Neglected tropical diseases (NTDs) are a major public health burden which mainly affects poor populations living in tropical environments and hard-to-reach areas. The study sought to examine coverage of preventive efforts, and case surveillance for NTDs in hard-to-reach communities in Ghana.The study investigated treatment efforts for lymphatic filariasis (LF), and onchocerciasis and schistosomiasis/soil transmitted helminths (SCH/STH) at household level, in difficult-to-access communities in Ghana. A total of 621 households were sampled from 6 communities in the Western, Oti and Greater Accra regions.Over 95% of the households surveyed were covered under mass drug administration (MDA) campaigns for lymphatic filariasis (LF) and onchocerciasis. More than 80% of households had received at least two visits by community drug distributors under the MDA campaigns in the last two years preceding the study. In addition, over 90% of households in the LF and onchocerciasis endemic communities had at least one member using anthelminthic medications under the MDA campaigns in the 12 months preceding the study. However, households where no member had taken anthelminthic medications in 12 months preceding the study were over 6 times likely to have someone in the household with LF.This study determined that SCH/STH, LF and onchocerciasis are of serious public health concern in some communities in Ghana. There is an urgent need for holistic practical disease control plan involving both financial and community support to ensure total control of NTDs in difficult-to-access communities is achieved.The online version contains supplementary material available at 10.1186/s12889-023-16652-1. Neglected tropical diseases (NTDs) are a major public health issue affecting poor populations living in tropical environment, and hard-to-reach areas , 2. AccoIn Ghana, unsafe health practices, limited access to safe water, poor sanitation, and a lack of awareness of the causes of NTDs continue to pose a serious challenge to achieving elimination of NTDs , 7. NoneAnopheles gambiae mosquitoes infected with the LF parasite (Wuchereria bancrofti) in communities where transmission is supposed to have been interrupted [Onchocerca volvulus in Simulium damnosum has been found in some communities where transmission is supposed to have been disrupted [Although progress has been made to reduce the burden of selected NTDs in Ghana , 14, howerrupted . Similarisrupted . In addiisrupted . Studiesisrupted . The success of NTD control programs relies on reducing pockets of disease transmission countrywide . As suchThese reasons underscore the need for studies that examine control efforts in at-risk populations in order to reduce the burden and control NTDs such as LF, onchocerciasis, and SCH/STH in Ghana . This stThe study was cross-sectional in design assessing interventions to control LF and onchocerciasis using a household survey among people living in difficult-to-access communities in Ghana.Data on LF were collected in two communities in the Western Region of Ghana – Old Bakanta and New Bakanta (both in the Ellembelle District). The study sites for onchocerciasis were Azua and Wui in the Nkwanta North District of the Oti Region. Data on SCH and STH were collected in Tuanikope and Pediatorkope in the Ada East District of the Greater Accra Region Fig. . These cIn each community, all households were eligible to be selected to take part in the survey. The total number of households in each community ranged between 60 and 250, depending on the size of the community. A simple random sampling approach was used to select households to participate in the study from May 2019 to September 2019. Estimated sample size was calculated based on the following: margin of error = 5%; design effect = 1; clusters = 1; confidence level = 95%. The combined sample size was 621 households. Table A household-level questionnaire was administered to heads of households (or the oldest adult household member) in the study communities  of the College of Health Sciences, University of Ghana . Written informed consent was provided by all adult participants.Univariate results were expressed as percentages  or means ± standard deviations (for continuous variables). Logistic regression analysis was used to assess the association between preventive measures and the prevalence of LF and onchocerciasis. The data were analysed with SPSS (version 23).Table The median monthly household income ranged from GHC150 (≈$27) in Azua, to GHC350 (≈$63) in Wui. The average household size was 5.8, although in the community of Azua, the average household size was higher (7.3)  of the respondents reported that water for the household use was from unprotected sources (such as surface water and borehole). All other household heads (45%) reported that water for their household use was from protected sources (such as pipe in the house or public tap/standpipe). More than half of household heads (53%) reported lack of a toilet facility, and indicated that members of the household as a result practiced open defecation.Approximately 96% and 98% of households in the LF and onchocerciasis endemic communities were covered under MDA campaigns Table . FurtherIn addition, 90% and 95% of households in the LF, and onchocerciasis endemic communities had at least one member using anthelminthic medications under the MDA campaigns in the 12 months preceding the study Table . In the Table Adjusted odds ratio analyses revealed that households where no member had taken anthelminthic medications in the 12 months preceding the study were over 6 times more likely to have someone in the household with LFLymphatic filariasis (LF), onchocerciasis, schistosomiasis, and soil transmitted helminths are important neglected tropical diseases in sub-Saharan Africa, including Ghana. This study investigated treatment efforts for lymphatic filariasis (LF) and onchocerciasis at the household level in difficult-to-access communities in Ghana. Findings from this study revealed households where no member had taken anthelminthic medications in the 12 months preceding the study were over 6 times likely to have someone in the household with LF, and self-reported household prevalence for onchocerciasis was higher compared to LF and SCH/STH. This finding corroborates the assertion that even though a combination of effective vector control and access to treatment will reduce the prevalence of LF in communities, MDA is a more effective control strategy . This stThis study revealed that the majority of households covered under preventive treatment for LF and onchocerciasis had received at least two MDA visits in the last two years preceding the study and had at least one household member using anthelminthic drugs within the last year preceding the survey. On the contrary, there had been no MDA visits in the SCH/STH endemic communities in the last two years preceding the survey, and only 5% of households reported using anthelminthic drugs in the last year. These findings suggest that control strategies for NTDs have been unequal in difficult-to-access communities in Ghana. In addition, it has been suggested that to help control NTDs, there should be sustained, expanded, and extended drug access programs to ensure the necessary supply of drugs, as well as addressing identified drawbacks to improve the effectiveness of other interventions . StudiesHowever, taking into account the logistical challenges associated with MDA and other vector control interventions, achieving coverage of the entire population is hardly ever achieved, particularly in difficult-to-access communities, and this results in residual infections . TherefoThe implementation of semi-annual community-wide MDA in the SCH/STH endemic study communities should be vigorously pursued and sustained. Evidence from previous studies in similar settings show that MDA programs have been largely effective against SCH and STH particularly among school-age children , 25.Optimizing surveillance, and improving the success rates of the MDA and other vector control programs in Ghana depends in large part on visits facilitated by CDDs. The findings suggest that CDDs in communities where NTDs are endemic should be given well-defined mandates, regularly trained, and supervised, and given the necessary resources to execute their mandate considering the relative precarious circumstances in the communities they serve. Over time, this will guarantee the success of strategies to control and possibly eliminate NTDs in difficult-to-access communities.Additional file 1: S1. File Household Questionnaire-2.


Background and aims: Patients frequently have concerns about their disease and find it challenging to obtain accurate Information. OpenAI’s ChatGPT chatbot (ChatGPT) is a new large language model developed to provide answers to a wide range of questions in various fields. Our aim is to evaluate the performance of ChatGPT in answering patients’ questions regarding gastrointestinal health. Methods: To evaluate the performance of ChatGPT in answering patients’ questions, we used a representative sample of 110 real-life questions. The answers provided by ChatGPT were rated in consensus by three experienced gastroenterologists. The accuracy, clarity, and efficacy of the answers provided by ChatGPT were assessed. Results: ChatGPT was able to provide accurate and clear answers to patients’ questions in some cases, but not in others. For questions about treatments, the average accuracy, clarity, and efficacy scores (1 to 5) were 3.9 ± 0.8, 3.9 ± 0.9, and 3.3 ± 0.9, respectively. For symptoms questions, the average accuracy, clarity, and efficacy scores were 3.4 ± 0.8, 3.7 ± 0.7, and 3.2 ± 0.7, respectively. For diagnostic test questions, the average accuracy, clarity, and efficacy scores were 3.7 ± 1.7, 3.7 ± 1.8, and 3.5 ± 1.7, respectively. Conclusions: While ChatGPT has potential as a source of information, further development is needed. The quality of information is contingent upon the quality of the online information provided. These findings may be useful for healthcare providers and patients alike in understanding the capabilities and limitations of ChatGPT. Gastrointestinal (GI) complaints and symptoms account for approximately 10% of all general practice consultations  and are AI chatbots employ deep learning-based natural language processing (NLP) that evaluates natural human language input and replies accordingly in a conversational mode . These mThe recent release of OpenAI’s ChatGPT in November 2022  has garnThe effectiveness of large language models in answering patients’ questions in the field of gastroenterology has not yet been thoroughly evaluated. In this paper, we aim to evaluate the performance of OpenAI’s ChatGPT chatbot in answering patients’ questions concerning gastrointestinal (GI) topics. This evaluation will focus on several key areas, including the accuracy and clarity of the information provided, the ability of the model to handle a wide range of questions, and the overall effectiveness of the model in addressing patients’ concerns and providing them with the information they need to make informed decisions about their health.Our evaluation aims to provide insights into the capabilities and limitations of large language models in answering patients’ questions in various gastroenterology subjects. Ultimately, our goal is to contribute to the ongoing development of large language models and their use in the field of gastroenterology, with the aim of improving the quality of care and information available to patients.To evaluate the performance of the newly- released large language model, OpenAI’s ChatGPT chatbot, in answering patients’ GI-related questions, we conducted a comprehensive study using a representative sample of real-life questions from patients in this field. The study was designed to assess the accuracy and clarity of the information provided by the chatbot, as well as its overall effectiveness in addressing patients’ concerns and providing them with the information they need to make informed decisions about their health.The study sample consisted of 110 real-life questions from patients in the field of gastroenterology, gathered from open internet sites providing medical information to diverse patients’ questions. These questions were selected to cover a wide range of topics, including common symptoms, diagnostic tests, and treatments for various gastrointestinal conditions. The questions were selected to reflect the types of questions typically asked by patients in gastroenterology and to provide a representative sample of the types of questions that the chatbot would encounter in a real-world setting.The questions were provided to the OpenAI chatbot and the answers were recorded. The answers provided by the chatbot were then assessed in consensus by three experienced gastroenterologists, each with more than 20 years of experience. All gastroenterologists work in a tertiary medical center, as well as in community clinics, and together cover all sub-specializations of gastroenterology: IBD experts, motility, hepatology, nutrition, and advanced endoscopy.The physicians graded each chatbot answer according to a scale of 1–5  in 4 categories: accuracy, clarity, up-to-date knowledge, and effectiveness in a consensus agreement between all three gastroenterologists. Since the questions were divided according to specific topics—common symptoms, diagnostic tests, and treatments—results are shown in a separate table for every topic. (Python (Ver. 3.9) was used for all statistical calculations. The average score ± standard deviation (SD) was calculated for each category and is shown in a table. A distribution graph of the answer grades for all groups by answer category was plotted. A Kruskal–Wallis one-way analysis of variance was used to determine the statistical difference between the groups.Overall, 110 various typical patient questions were presented to the OpenAI chatbot. Forty-two included various questions regarding treatment options in diverse gastroenterology fields. Questions were chosen to include the whole spectrum of specification from very specific questions  to wider questions not referring to definite disease staging or severity . All questions chosen were short and clear for better standardization. The results of the evaluation for the treatment questions are shown in A full list of all questions and answers is presented in the Overall, the OpenAI chatbot answers to the questions dealing with treatment options varied wildly between the different topics and were inconsistent in their level. Notably, at the end of almost all the answers, the patient is referred to a doctor/healthcare provider for further evaluation.The results of the evaluation for questions related to symptoms are shown in The results of the evaluation for questions related to diagnostic examinations are shown in Diversity in the quality of answers to the diagnostic examination was the highest of all groups. While many answers were correct and informative, other medical terms were simply not recognized by the chatbot .As shown graphically in p = 0.019) and up-to-date (p = 0.009), but not for the subjects of clarity (p = 0.071) and efficacy (p = 0.071).Statistical difference between the groups was shown for the subjects of accuracy (Overall, our study provides a comprehensive evaluation of the performance of a large language model, OpenAI’s ChatGPT chatbot, in answering patients’ questions in the field of gastroenterology. The results of the study will hopefully be valuable for healthcare providers and patients alike, as they will provide important insights into the capabilities and limitations of these models in providing accurate and reliable information about gastrointestinal health.Generally, the results of our evaluation of OpenAI’s ChatGPT large language model, as a potential tool for answering patients’ GI-related questions, are concerning. Despite the impressive capabilities of this model in other applications, our study found that it was insufficient for reliably answering patients’ questions in this domain.In our study, we presented the model with a range of common gastroenterological questions and assessed its ability to provide accurate and helpful responses. While the model could generate responses for all questions, the accuracy and helpfulness of these responses varied significantly. In many cases, the model’s responses were either incomplete or entirely incorrect, indicating a lack of understanding of the subject matter.These findings are particularly concerning given the importance of accurate information in the medical field. Patients often rely on Internet information to make decisions about their health and well-being, and inaccurate information can have serious consequences. As such, it is essential that any tool used to provide medical information to patients be able to provide accurate and reliable responses.Interestingly, while the answers to treatment-based questions and symptom-based questions showed a similar and relatively steady quality and effectivity , diagnosFurthermore, our study also highlighted the limitations of OpenAI’s ChatGPT chatbot in the medical domain. The ability to understand and accurately respond to complex medical questions requires a deep understanding of the subject matter, as well as the ability to process and integrate information from a variety of sources . While COur results are in line with previous data assessing other artificial intelligence conversational agents in healthcare ,7,11. AsRecent data from the last months suggest that LLMs hold the potential for significant impacts in medicine ,13.In our previous work, we examined the utility of ChatGPT in identifying top research questions in gastroenterology. Our conclusion was that ChatGPT may be a useful tool for identifying research priorities in the field of GI, yet we noted the need to improve the originality of the research questions identified .In telehealth, LLMs such as ChatGPT could improve efficiency and scalability, and provide unbiased care . DespiteSignificantly, it is worth mentioning that all of these studies have been published within the recent months subsequent to the initial release of the inaugural version of ChatGPT. This accumulation of research findings attests to the remarkable potential impact and significance that ChatGPT holds for the field of medicine in the foreseeable future.Our study had a few limitations. First, the choice of questions naturally influenced the answers obtained by the OpenAI chatbot. However, the wide variety of questions and their relatively high number minimized the chance for bias. Furthermore, the answers were graded with the consensus of three physicians; there is a possibility that other physicians might have had a different point of view. Nevertheless, to minimize that risk, we chose highly experienced gastroenterologists with wide clinical experience and more than 70 years of practicing gastroenterology both in a tertiary medical center and in community practice. Lastly, there were no comparisons with other chatbots to gauge the relative merits of ChatGPT against other similar technologies, and no blinded comparison between human and chatbot answers was performed. These research directions necessitate further dedicated exploration to explore and investigate its potential in greater detail.Importantly, our study did not include patients’ comments and, therefore, is not valid in terms of assessing patients’ points of view. This merits further specific research.Overall, our study suggests that caution should be exercised when considering the use of a large language model, such as OpenAI’s ChatGPT, for providing medical information to patients. While the model has the potential to be a powerful tool, it is not yet ready to be relied upon for this critical task. Further research and development are needed to improve its capabilities in the medical domain before it can be used with confidence.


Self-healing graphene- and MXene-based composites can be deployed in wearable sensors, supercapacitors, anticorrosive coatings, electromagnetic interference shielding, electronic-skin, and soft robotics.Self-healing graphene- and MXene-based composites have shown improved electrical conductivity, mechanical properties, healing efficacy, and energy conversion efficacy.Self-healing structures can open up considerable new horizons in the future of healthcare, sensors, electronics, robotics, supercapacitors/batteries, coatings, and biomedicine. Today, self-healing graphene- and MXene-based composites have attracted researchers due to the increase in durability as well as the cost reduction in long-time applications. Different studies have focused on designing novel self-healing graphene- and MXene-based composites with enhanced sensitivity, stretchability, and flexibility as well as improved electrical conductivity, healing efficacy, mechanical properties, and energy conversion efficacy. These composites with self-healing properties can be employed in the field of wearable sensors, supercapacitors, anticorrosive coatings, electromagnetic interference shielding, electronic-skin, soft robotics, etc. However, it appears that more explorations are still needed to achieve composites with excellent arbitrary shape adaptability, suitable adhesiveness, ideal durability, high stretchability, immediate self-healing responsibility, and outstanding electromagnetic features. Besides, optimizing reaction/synthesis conditions and finding suitable strategies for functionalization/modification are crucial aspects that should be comprehensively investigated. MXenes and graphene exhibited superior electrochemical properties with abundant surface terminations and great surface area, which are important to evolve biomedical and sensing applications. However, flexibility and stretchability are important criteria that need to be improved for their future applications. Herein, the most recent advancements pertaining to the applications and properties of self-healing graphene- and MXene-based composites are deliberated, focusing on crucial challenges and future perspectives. As. As2) na3C2Tx) were introduced into paraffin matrix to obtain composites with EMI shielding effectiveness (SE) of ~ 39.1 dB at 60 wt% MXenes loading ..−π conjuA graphene-based supercapacitor was designed for storing energy, which could be recharged in short times. Graphene supercapacitor technology is safer than present battery technology since it can work without discharge or high temperature . Graphen, in which rGO had efficient electrical conductivity and SnO2-informed energy storage abilities. On the other hand, supersonic spraying of rGO could decrease the peak ratio due to the self-healing effect. Supersonic spraying helped the good adhesion among the SnO2-decorated rGO flakes. The concentration effect of SnO2 on the electrochemical activity of the supercapacitors was also investigated; the best coating situations were recognized. Accordingly, the combination of rGO and SnO2 could increase the charge transport inside the electrode, finally enhancing the electrochemical performance. The porous construction of the fabric permitted the adequate electrolyte diffusion into the SnO2 or rGO to stimulate the function among the electrolyte with the electrode. The optimal sample displayed the greatest capacitance of 1008 mF cm−2, with the capacitance retention of ~ 93%. Stretching tests up to N¼ 1100 revealed the mechanical durability of the prepared supercapacitor, which was appropriate for generating energy storage systems on wearable fabrics -rGO composite electrode was introduced, joining high specific surface area of rGO and excellent conductivity of the MXene to inhibit the self-restacking of the structure and resist the low oxidization of MXene. Besides, this composite exhibited good mechanical properties than pure rGO aerogels; the MXene/rGO/PU aerogel provided a great area-specific capacitance of 34.6 mF cm−2 at a scan rate of 1 mV s−1. The 3D composite also displayed an outstanding self-healing capability with specific capacitance retention of 81.7% after the fifth healing according to the PU properties. The formation of this self-healable can offer an assay for manufacturing long-life electronic devices needs [Self-restacking and accumulation of MXenes are commonly predictable throughout drying and electrode formation procedures due to the robust van der Waals interaction among neighboring nanosheets, which restricts the ion passage and decreases the active site in supercapacitors. Thus, the use of graphene between MXene layers can perform as a perfect spacer to inhibit the stacking among the MXene nanosheets, which aids to increase the electrochemical properties of the MXene –115. A 3Non-chemotherapeutic cancer and tumor therapy has gained significant consideration due to its lower side effects and unique targeting properties. GO nanoparticles may lose their stability (in vivo), because of possible aggregations when exposed in physiological environment after dispersion in solutions. Thus, surface modification techniques can be applied for improving the stability of these materials. Self-healing hydrogels were designed via Schiff-base linkage using chondroitin sulfate multialdehyde (CSMA), branched polyethylenimine (BPEI), and BPEI-conjugated GO (BPEI-GO) for targeted breast cancer therapy. Surface modification was deployed for enhancing the stability of these hydrogels using BPEI. These hydrogels could be doped in the network and provided targeted drug delivery and NIR-triggered photothermal therapy Fig. . They diA PEG-CMC/needle-like nano-hydroxyapatite (HAP)/GO nanocomposite hydrogel exhibited a construction with efficient injectability and good self-healing properties for tumor proliferation prevention and photothermal therapy. In vitro assessments revealed that GO was toxic to tumor cells, and HAP could prevent the proliferation of tumor cells; this composite was not transferred to the normal cells and did not led to cell damage. The breast cancer tumor-bearing mice were treated with a PEG-CMC/HAP/GO composite hydrogel (in vivo). This self-healing hydrogel successfully obstructed the tumor cell proliferation, showing suitable photothermal effects for targeted cancer therapy .As mentioned above, both graphene and MXenes have interesting features that make them appropriate to be applied in the structure of self-healing composites; however, they also have some limitations that could restrict their clinical applications and necessitate conducting more research for overcoming these limitations. For instance, although evidence showed the short biocompatibility of MXenes (in cell culture tests), the long-term biosafety of these compounds is not completely assessed yet and more experiments are needed for confirming their safety for further biomedical uses. Indeed, due to the young age of this technology, our information about the immunogenicity, biocompatibility, biodistribution, and pharmacokinetics of different forms of MXenes is not comprehensive and several analyses on both small and large animal models are needed in this case , 120.One of the important points for controlling different features of nanomaterials is their synthesis method. So far, a few attempts have been made for the fabrication of MXenes via bottom-up methods and they are commonly prepared via top-down methods leading to the preparation of multi-layer MXenes with less controllable structural and morphological features. Accordingly, still, the properties of naked MXenes with pure surface terminal groups have not been tested due to the absence of bottom-up methods for the fabrication of pure MXenes . In the −1); these composites were designed by incorporation of mussel-inspired protein polydopamine. The significant stability and mechanical properties as well as adhesiveness (the adhesive strength was increased by 300%), self-healing, and fast recovery capabilities could be achieved due to presence of hydrogen bonding, covalent bonds, π−π stacking, and supramolecular interactions in these composites. Because of the enhancement in human embryonic stem cell-derived fibroblasts and cardiomyocytes cell viability and proliferation, after the utilization of these composite hydrogels, they can be considered as promising tissue engineering materials with both self-healing and electrical conductivity properties [One of the main challenges in designing hydrogels used in electroactive tissues is the deficiency in electrical conductivity and adhesiveness –126. Jinoperties .Graphene-based nanocomposite materials were developed with self-healing potentials without external forces, which had quick electrical recovery from damages. They had steady electrical resolution even when the cyclic test was done up to 150 cycles. These materials can be employed to design bio-electronic sensor devices with excellent permanency . In one 3C2) nanosheets through an etching technique and modification process utilizing 3-aminopropyltriethoxysilane. As the corrosion inhibitors, cerium (Ce3+) cations were introduced and encapsulated within MXene nanosheets to obtain self-healing epoxy composite coatings, showing good corrosion protection performance [Despite these limitations, the self-healing composites of graphene and MXenes are promising materials with bright future, especially for the fabrication of innovative and smart products in biomedical applications. They could be applied for the fabrication of E-skin, anticorrosion coating, and intelligent sensors. For instance, a type of self-healing composite of bio-based polyschiff vitrimers and GO was synthesized by Jia et al.  to be apformance . In addiformance .3C2Tx)/PVA hydrogel electrode with specific features like self-healing capability and stretchability was fabricated for E-skin applications. The presence of MXene in the structure of this E-skin leads to an enhancement in its self-healing ability and conductivity. This electrode shows excellent stretchability and self-healing properties . The sensor could recover its activity after a self-healing test, showing excellent potential for human motion monitoring [In recent years, E-skin with interesting features like self-healing, versatile sensory capability, and stretchability is one of the interesting fields of science that will have prospective applications in soft robotics, artificial intelligence devices, and personalized medicine. E-skin has similar functionalities as human skin such as self-healing properties, stretchability, and flexible sensory ability, which can be deployed in soft robotic systems, artificial intelligence devices, etc. , 134. Thnitoring . A componitoring . These aAlthough MXenes have distinct features and have shown promising potential for various applications, there are still some obstacles in the way of their commercialization and clinical implementation . One of Graphene and MXene-based composites have been developed with fascinating self-healing properties. Different literature has been accompanied on the limitations of graphene and MXenes on strength, mechanical potential, and response to external forces in the self-healing field. In addition to rheological recovery tests, the gelation, injectable, stretchable, and cut-heal properties ought to be comprehensively evaluated; the pH-responsive behavior and swelling behavior/swelling kinetics of the self-healing hydrogels should be analytically studied. Graphene-based materials have exceptional electrical, mechanical, and thermal properties and good energy absorption. Although more information is needed in graphene applications, especially regarding the applicability of self-healing graphene-based composites and understanding of their related mechanisms, the design of high-performance structures using polymers in combination with graphene and its derivatives still needs additional explorations.It is necessary to fully understand the related mechanisms of self-healing materials based on graphene and MXenes to design novel composites with multifunctionality. On the other hand, MXenes are exceptional, because they have great interlayer spacing, good electrical conductivity, unique architectures, and virtuous thermal stability. According to the great conductivity of MXenes, their composites displayed good conductivity, which could be applied in the self-healing process. MXenes exhibited greater electrochemical properties than other 2D nanomaterials such as graphene. Some of their properties such as abundant surface terminations and great surface area are important to evolve biomedical and sensing applications. However, flexibility and stretchability are crucial aspects that should be improved for their future practical applications. Several conductive graphene- and MXene-based composites with suitable elasticity and stretchability can be developed only after specific optimization processes as well as suitable surface modifications; these composites can be employed in different fields of sensitive strain sensors, health monitoring, E-skin, soft robotics, etc. Tough, the fabrication of these conductive materials with outstanding mechanical features, self-healing features, and sensitivity/selectivity is still an important challenging issue. Additionally, when the concentration of MXenes in a polymer matrix increases, the conductive network of MXene fragments is not break in the anticipated strain range. However, some of their limitations can be overwhelmed through the surface functionalization/modification as well as hybridization of MXenes; surface modification is essential to increase the attraction among the MXenes with the polymeric matrix. Due to their high reactivity, it is possible to perform several surface modification reactions by hydroxyl groups on the surface of MXenes.


The combined effect of temperature and humidity on the fracture toughness of aluminium alloys has not been extensively studied, and little attention has been paid due to its complexity, understanding of its behaviour, and difficulty in predicting the effect of the combined factors. Therefore, the present study aims to address this knowledge gap and improve the understanding of the interdependencies between the coupled effects of temperature and humidity on the fracture toughness of Al–Mg–Si–Mn alloy, which can have practical implications for the selection and design of materials in coastal environments. Fracture toughness experiments were carried out by simulating the coastal environments, such as localised corrosion, temperature, and humidity, using compact tension specimens. The fracture toughness increased with varying temperatures from 20 to 80 °C and decreased with variable humidity levels between 40% and 90%, revealing Al–Mg–Si–Mn alloy is susceptible to corrosive environments. Using a curve-fitting approach that mapped the micrographs to temperature and humidity conditions, an empirical model was developed, which revealed that the interaction between temperature and humidity was complex and followed a nonlinear interaction supported by microstructure images of SEM and collected empirical data. Al–Mg–Si alloys are commonly used in various structural applications like aircraft wings, rotor blades , and mar2O3, CuO, ZnO, etc., is observed in marine water above 30–80 °C [The ability of aluminium to resist corrosion is linked to the durability of the naturally formed oxide layer that protects its surface. However, aluminium is prone to pitting corrosion in a higher pH range (8.1 for marine water) at room temperature and 80 °C . Althoug30–80 °C . Above 730–80 °C . Corrosi30–80 °C .Moreover, temperature can potentially raise the salinity levels of seawater and consequently increase its aggressiveness due to evaporation . The evaThe weather data show that the temperature in Middle Eastern regions can reach nearly 60 °C during the summer months . High amThus, a comprehensive approach is required to relate the interdependency of humidity and temperature with Al–Mg–Si–Mn alloy properties in a corrosive environment. However, there are few studies on the environmental failure behaviour of aluminium alloys, especially cracking failure recurrence behaviour under varying temperature or humidity conditions, but not combinedly. Studying the combined effect of temperature and humidity on the material’s fracture toughness is essential in this connection. The present study aims to investigate the fracture toughness of the Al–Mg–Si–Mn alloy under the specific conditions of a coastal environment, considering the influence of varying temperatures and humidity. The novelty of this work lies in three key aspects. First, it involves a thorough investigation of fracture toughness in a coastal environment, which is crucial due to the unique challenges caused by high humidity and potential exposure to corrosive elements. Second, an empirical model has been developed to accurately predict the fracture toughness values, offering valuable insights for engineering applications and material design in coastal environments. Lastly, a novel methodology has been adopted to analyse the nonlinear variation resulting from the combined effect of temperature and humidity by mapping micrographs with the obtained curve. This comprehensive analysis method provides a deeper understanding of the intricate interactions and nonlinear behaviour exhibited by the Al–Mg–Si–Mn alloy in response to changing environmental conditions.Aluminium 6082, called Al–Mg–Si–Mn alloy, is frequently used in structural applications . Referri−6/K.The T651 state, which prevents elastic recovery after processing, is attained using solution treatment, stress relief by stretching, and artificial ageing at a temperature of about 180 °C. The properties of Al–Mg–Si–Mn alloy in the T651 condition were density = 2.71 g/cc, tensile strength = 348 MPa, yield strength = 320 MPa, elastic modulus = 70 GPa, elongation = 17.5% . Due to Al–Mg–Si–Mn alloy sheet 16 mm thick was machined to prepare the compact tension (C(T)) specimen as per the required geometry, as illustrated in The pre-cracked C(T) specimens were immersed in a 3.5 weight per cent NaCl solution at room temperature for 7 days [In the coastal environment of the Middle East, the temperature can rise as high as 60 °C, while the operating temperature of machine components may reach up to 70 °C. Therefore, a temperature range of 20 °C to 80 °C was selected to encompass these conditions. Additionally, the humidity in the Middle East region can vary between 40% and 90%.On a servo-hydraulic testing machine with a load capacity of 100 KN, fracture toughness investigations on C(T) specimens were carried out by maintaining a frequency of 3 Hz. From the fracture toughness testing, the load applied and strain gauge readings were recorded and analysed by plotting the load versus COD plot. QP) value using curve fitting techniques, specifically by drawing a 5% secant line to the maximum load (Pmax) on the experimental data. The plots show that all load versus COD curve cases match the type III curve [Pmax = QP. Moreover, P5 as shown in II curve ,26, whicFrom plots of load vs. COD, it can be observed that as the humidity increases, the load-carrying capacity of an Al–Mg–Si–Mn alloy decreases. A humidity level of 40% at a temperature of 20–80 °C typically does not significantly impact the load-carrying ability of aluminium, as aluminium is generally not susceptible to moisture absorption or degradation . From FiQK is calculated from each test’s QP value and the measured crack length using Equation (1). Along with Equations (2) and (3), the Pmax/QP ratio satisfies the normative criteria for obtaining the linear elastic plane strain fracture toughness. The primary result of the experimental tests is load-displacement curves.Using Equation (1) , conditiB). When the thickness of the specimen reaches the significant limit, the fracture toughness value seems fairly steady. It is referred to as plane strain fracture toughness, represented by KIc. In Equations (2) and (3) [NB is the thickness of the specimen at notch, B is the thickness of the specimen. The primary determinant of fracture toughness is specimen thickness ( and (3) , the fola) and thickness (B) of the specimen must be greater than 12.9 mm and width of the specimen (W) must be greater than 26 mm for the provisional fracture toughness (QK) obtained. However, specimens considered for the present work have a = 27 mm and W = 50 mm. The fracture toughness of the Al–Mg–Si–Mn alloy for various temperature and humidity conditions is calculated using Equation (1).The dimensions considered here fulfil the conditions of plane strain fracture toughness. As per Equations (2) and (3), the crack length , is assumed to be necessary to confirm the composition of the bright area and the presence of phase particles. The EDS mapping shows that as the temperature increases from 20 °C to 80 °C, the contents of Mg and Si improve ,38. ThisApart from Al, Si, Mg, and O, the EDS examination of the particles shown in When Al–Mg–Si–Mn alloy is subjected to atmospheric corrosion, it undergoes a complex series of chemical reactions that can form various corrosion products, as shown in 2Si [When Al–Mg–Si–Mn alloy is exposed to an increasing temperature at high humidity, the protective oxide layer on the surface of the alloy can break down, leading to increased corrosion rates. As a result, corrosion products might form on the surface of the alloy, which can include metal ions such as copper Cu and Zn and Mg2Si , as showAl–Mg–Si–Mn alloy-subjected corrosion reactions in humidity environments result in hydrogen absorption into aluminium alloy during deformation. The deformation primarily occurs in the region where the hydrogen concentration is critical. The metal lattice fractures once the critical deformation is attained in the particular localised zone placed ahead of the crack tip . When sp2 gas, as shown in Equation (4) presented below [The reduction in water at the alloy surface can produce hydrogen atoms that have the potential to be absorbed into the alloy and then recombine to form Hed below ;2Al (s)In general, the effect of humidity and temperature on Al–Mg–Si–Mn alloy can lead to complex changes in its properties, and the resulting curves may not necessarily be linear. Al–Mg–Si–Mn alloy is susceptible to corrosion when exposed to high humidity and certain temperatures. The degree and rate of corrosion can depend on various factors, including the humidity level, temperature, presence of other chemicals, and duration of exposure. However, experiments carried out by various researchers describe that the effect of humidity  and tempThe fracture toughness experiments were carried out for various couple loads such as temperature 20 to 80 °C and humidity 40 to 90% on Al–Mg–Si–Mn alloy. The results obtained emphasise the possibility that humidity and temperature variations may have contributed to the scatter of results. For these scattered points, it is required to fit the curve to find a mathematical function that best approximates a set of data points. This also helps to identify trends, make predictions, and provide insight into the underlying mechanisms of fracture toughness under coastal region temperature and humidity conditions. T—Temperature in °C, H—Humidity in %. In MATLAB, polynomial functions of two variables were employed to model the complex relationships between temperature and humidity on fracture toughness. Using these polynomial functions, coefficients were assigned by the weights to determine the shape of the surface . Curve-fThe coefficient of determination of the regression model, R-square, is 0.983. The curve fitting for the scatter plots shown in In the case of the Al–Mg–Si–Mn alloy being studied, the nonlinear variation of results is evident in the fact that cracks and corrosion on the surface are inconsistent across all environmental conditions. For example, at 50% humidity, the cracks are deeper and more pronounced. In contrast, at 70% humidity, there is evidence of broken particles, and at 90% humidity, the HELP mechanism is observed, as shown in At 40 °C and 50% humidity, there is a crack path between two oxide layers with a significant decrement in fracture toughness. At 40 °C and 70% humidity, there are cracks in the dimples with oxide layers indicating degradation. At 40 °C and 90% humidity, there are only dimples with stable fracture toughness values, as shown in At 60 °C and 50% humidity, the SEM images show deeper dimples and cracks between oxide layers with a significant decrement in fracture toughness, indicating a degraded state of the material. At 60 °C and 70% humidity, SEM images reveal a sign of precipitates and a crack path away from the precipitates with stable fracture toughness values. This suggests that precipitates in the material under certain environmental conditions can lead to more stable behaviour. At 60 °C and 90% humidity, the SEM images show only the cracks with a further reduction in fracture toughness values, indicating a high level of degradation, as shown in The mapping of SEM images using the curve fitting technique indicates that the material’s behaviour is nonlinear under different environmental conditions. At 80 °C and 50% humidity, SEM images show a crack path away from the oxide region with a little decrement in fracture toughness. At 80 °C and 70% humidity, SEM images reveal dimple cracks without an oxide layer and a significant decrement in fracture toughness. At 80 °C and 90% humidity, the SEM images show precipitation ) to predict the mechanical behaviour of the studied material under different environmental conditions. The accuracy and reliability of the model were evaluated by comparing the model predictions with the experimental results. The experimental fracture toughness values and the calculated fracture toughness values using the empirical model (Equation (5)) are compared in The low error rate indicates that the empirical model successfully accurately predicted the mechanical behaviour of the studied material under different environmental conditions. This is an important finding, as it demonstrates the ability of the empirical model to capture complex microstructural changes that can influence a material’s mechanical properties. The investigation of interdependencies between the coupled effects of temperature and humidity on fracture toughness of Al–Mg–Si–Mn alloys has provided significant insights into the behaviour of these materials under real-world conditions. The following are the conclusions drawn from the investigation:Based on the microstructure analysis conducted in this study, it was observed that the presence of phase particles at higher temperatures increased the fracture toughness of the Al–Mg–Si–Mn alloys. However, the results also indicated that higher humidity levels led to the formation and distribution of more of these particles, which resulted in a decrease in fracture toughness due to increased stress concentration. The formation of micro-voids due to increased humidity levels in the Al–Mg–Si–Mn alloys might result in hydrogen gas entrapment, leading to hydrogen embrittlement. This process is associated with a reduction in fracture toughness and an increase in crack propagation.The results of the fracture toughness test and microstructural analysis have shown that temperature and humidity have a nonlinear, interdependent relationship that can significantly impact the alloys’ fracture toughness.Furthermore, the developed empirical model has proven to be an effective tool for predicting the fracture toughness of Al–Mg–Si–Mn alloys under different temperature and humidity conditions. This study provides essential information to the scientific community about the interdependencies between temperature and humidity on the fracture toughness of Al–Mg–Si–Mn alloys. The model can be used to optimise the selection and design of materials in coastal environments.


In this paper, we investigate the electromagnetic response of metasurfaces due to excitation of the toroidal moment. A toroidal curved metasurface analyzad using a novel theoretical solution based on the Fourier analysis to evaluate the localized fields. Analyzing localized near-field interactions are crucial in investigating the excited trapped modes and enables us to optimize the reflection properties of the proposed metasurface. Optimization is accomplished using graphene layer and resulted a hybrid dielectric-graphene structure with near-zero reflection properties. According to a recent study3, Greta Otto’s wings have asymmetrically dispersed nanostructures in the transparent areas Fig. 4. This observation motivates us to investigate analytical approaches of non-periodic nano-structures.A zero-reflection structure is required to achieve transparency. This characteristic is present in the wings of the remarkable species of butterfly known as Greta oto Fig. 5. A toroidal dipole is the third member of localized electromagnetic excitations which is created by a current circulating on the surface of a torus and has been observed in solid-state physics6. The toroidal response of metasurfaces was experimentally observed in microwave regime7 and then theoretically scaled to the THz regime8. The performances of these metasurfaces are usually limited by radiative and nonradiative losses where nonradiative losses can by reduced by employing materials of low loss such as dielectric10 likewise the solution employed in nontoroidal metasurfaces11.The electromagnetic response of metasurfaces can be related to traditional electric and magnetic dipoles or their complex combinations known as multipoles12. Trapped modes that excited in such asymmetrical structures are included in the the concept of bound states in the continuum (BIC)13. A strong link between the toroidal dipole resonance and the BIC was defined in the context of all-dielectric metasurfaces14. To construct a trapped mode supporting metasurface, we utilize a set of identical subwavelength unit cells with two asymmetric high-refractive index Silicon particles made in the form of modified nanodisks.Radiative losses can be regulated by designing the asymmetric all-dielectric unit cells to excite a high-quality factor resonant response known as Fano resonance in which the radiative damping can be efficiently suppressed by trapped mode and leads to the reduction of radiative lossesTrapped modes lead to a strong near-field enhancement where the located electromagnetic fields becomes notable. We utilize a novel theoretical approach to analytically evaluate localized electromagnetic fields near the all-dielectric unit cells of trapped mode supporting metasurface.16. To accomplish a comprehensive solution, we consider a cylindrical surface where any arbitrary surface can be fitted on a cylindrical surface with a defined cross-section.This evaluation provides the capability of manipulating the reflection coefficient for the surface. Our investigations should support every possible surface shape in the practical applications of such metasurfaces as sensingSince all-dielectric curved metasurfaces are composed of multi subwavelength cells, their optical properties are related to resonant features of each constitutive unit cell resonator and its mutual interaction with the other cells, trapped mode excitation does not merely satisfy the high-Q and zero-reflection properties which necessitates computing the localized electromagnetic fields to optimize such curved multi-cell metasurfaces.The sampled curved metasurface was selected as entclass1pt{minimaGraphene is selected to optimize the obtained reflectivity from evaluated electromagnetic fields. Optimization can be implemented by varying the graphene chemical potential when the graphene layer is integrated with the proposed dielectric structure.6. c indicates the speed of light in free space. Equation  do not merely provide the high quality properties for proposed curved structure and accentuates our introduced novel approach for determining localized electromagnetic fields. Consequently, any practical surface with random and arbitrary curve can be optimized by utilizing the near-field responses. To figure out the functionality of the procedure, a reasonable segment of the designed Silicon metasurface is optimized using graphene ribbons and strip lines which results near-zero reflectivity properties for the structure. To bias graphene sheets empirically, one can apply an external voltage to the sheets using a voltage source or bias tee. Graphene can be indirectly stimulated by applying thin gold electrodes on the side borders of the structure and mounting the graphene layers onto them. By applying stimulation to the metal electrodes, the graphene layers can be activated or manipulated to achieve the desired conductivity or impedance properties. It is important to note that the exact procedure for mounting and stimulating graphene layers may depend on the specific experimental setup and conditions, and may require careful calibration and optimization to achieve the desired results


In the first part of the review article “General considerations” we give information about conventional flexible platforms and consider the advantages and disadvantages of paper when used in humidity sensors, both as a substrate and as a humidity-sensitive material. This consideration shows that paper, especially nanopaper, is a very promising material for the development of low-cost flexible humidity sensors suitable for a wide range of applications. Various humidity-sensitive materials suitable for use in paper-based sensors are analyzed and the humidity-sensitive characteristics of paper and other humidity-sensitive materials are compared. Various configurations of humidity sensors that can be developed on the basis of paper are considered, and a description of the mechanisms of their operation is given. Next, we discuss the manufacturing features of paper-based humidity sensors. The main attention is paid to the consideration of such problems as patterning and electrode formation. It is shown that printing technologies are the most suitable for mass production of paper-based flexible humidity sensors. At the same time, these technologies are effective both in the formation of a humidity-sensitive layer and in the manufacture of electrodes. Lately, a new trend has appeared with the integration of sensors directly on flexible plastic foils. Their flexibility and their simplified processing, targeting the production on large area using roll to roll and printed electronics processing see , bring nIn conventional Si microelectronics, patterning is most often done using photolithography, in which the active material is deposited initially over the entire substrate area, and selected areas of it are removed by physical or chemical processes. Despite its high resolution, the photolithographic process is very complex, expensive, uses extremely expensive equipment, requires many steps, is time consuming, subtractive, and only suitable for patterning of small areas.In addition, the harsh conditions required to dissolve the resists, etch the underlying layers, and remove the photoresist destroy the activity of most organic electronic materials. De Rooij and co-workers ,5 believIn addition, flexible substrates are ideal for deployment on curved surfaces, for integration on cloths for application in wearable sensors, smart textiles, or for development wireless radio frequency identification (RFID) tags for logistics applications . In thisCurrently, a large number of flexible sensors have been developed. These include gas and humidity sensors, photodetectors, strain sensors, pressure sensors, temperature sensors and biosensors ,20,21,22https://www.researchdive.com/171/humidity-sensor-market, accessed on October 2022). This growth will primarily be due to the miniaturization of electronic devices and the use of humidity sensors in various industries. Due to unique water properties, humidity greatly affects living organisms, including humans and materials. The amount of water vapour in the air can affect the human comfort, and the efficiency and the safety of many manufacturing processes, including drying of products such as paint, paper, matches, fur, and leather; packaging and storage of different products such as tea, cereal, milk, and bakery items; and manufacturing of food products such as plywood, gum, abrasives, pharmaceutical powder, ceramics, printing materials, and tablets. Moreover, industries discussed above are only a small part of the industries where the humidity should be controlled. In agriculture, the measurement of humidity is important for the plantation protection (dew prevention), the soil moisture monitoring, and so on [Humidity sensors are among the fastest growing sensor markets. The global humidity sensor market is predicted to grow by 7.5% per year in the coming years and reach $1551.9 million by 2026  be It should be noted that the field of paper-based sensors is developing rapidly, and significant progress has been made in the development of such sensors. At present, quite a lot of reviews on paper-based sensors have already been published ,55,56,57The review is organized as follows. It consists of two parts. In the first part of “General consideration” we give information about conventional flexible platforms and consider the advantages of paper for humidity sensor development as both a substrate and a humidity-sensitive material. Next, we discuss the manufacturing features of paper-based (PB) humidity sensors, their configuration, sensing materials and electrodes. Then, in the second part of this review “Humidity sensors performances”, we analyze the performance of paper-based humidity sensors manufactured using different approaches. Finally, we discuss the challenges encountered in the development and use of paper-based humidity sensors. Possible areas of application of PB humidity sensors are not considered in this article, since they are described in sufficient detail in the already published review articles mentioned earlier.One of the most fundamental challenges in the design of flexible electronic systems is the choice of substrate, because the material for such substrates must have a unique set of properties . No doubAt present, for substrates, flexible materials such as polyimide (PI), polydimethylsiloxane (PDMS), polyester (PE), polyethylene naphthalate (PEN), polytetraflouroethylene (PTFE), and polyethylene terephthalate (PET) are the most commonly reported ones ,60,61,62As follows from the previous discussion, the flexible organic materials play the irreplaceable roles in the substrates of flexible sensors because of their excellent flexibility and stability . HoweverPaper is a three-dimensional sheet formed by connecting cellulose fibers of different lengths through hydrogen bonds between hydroxyl groups. Paper is made from raw materials containing plant fibers through pulping, blending, and processing, and can be folded and cut as desired . The celThe most common types of paper used in the development of humidity sensors are filter paper, nitrocellulose paper and office paper. Filter paper made from pure cellulose has various properties. Important parameters are wet strength, porosity, particle retention, volume flow, compatibility, efficiency and capacity. According to the quality of the filter paper, it is divided into qualitative filter paper and quantitative filter paper. Qualitative filter paper is often used in qualitative analysis. The reason is that qualitative filter paper produces more cotton fibers if it is used for filtering. Quantitative analysis filter paper is made in such a way that the paper does not react with common chemicals during the production process. As a result, it produces fewer impurities and is used in quantitative analysis. There are different grades of filter paper depending on the size of the pores. In total, there are 13 different grades of the filter paper. The largest pore size is grade 4; the smallest pore size—grade 602 h; the most commonly used grades are 1 to 4. Quality grade 1 filter paper has a pore size of 11 µm.3) groups in the polymer structure. Nitrocellulose surface is more homogeneous, smoother and has fewer and narrower pores in comparison to chromatographic cellulose-based paper surface [Nitrocellulose is a cellulosic compound produced by treating common cellulose with a sulphuric/nitric acid mixture, resulting in the substitution of (-OH) groups to , card paper, and the like. As a rule, mineral fillers, such as calcium carbonate, chalk, and clays, are added to the paper base, usually in an amount of 10–20%, to fill the voids at the intersections of the fibers ,79. AddiIn addition to the above types of paper, it is also necessary to highlight the so-called nanopaper ,81,82,83The experiment showed that a wide variety of paper types can be used to develop sensors . The chaPaper-based sensors are considered to be a new alternative technology for making simple, low-cost and flexible electronic devices ,74,105. During the research and use of paper, it was found that the three-dimensional porous structure throughout the thickness of the paper with a large surface area makes it easy to absorb functional reagents, and, most importantly, allows selective processing of two sides of the paper with different or the same functions . In addiPaper as a dielectric material can be used in numerous sensing devices, especially capacitive-type sensors. In addition, the unique three-dimensional hierarchical architecture of cellulose fibers with different length scales allows the accommodate various active materials in substrates, opening up great opportunities for the development of advanced electronic devices. In this regard, in recent years, research has been carried out aimed at studying the possibilities of using paper substrates for the development of various sensors ,122,123.Moreover, cellulose fibres can be functionalized, thus changing properties such as hydrophilicity, if desired, as well as its permeability and reactivity . The surOf course, paper substrates are inferior to plastic ones in terms of mechanical strength, resistance to aggressive environments, and manufacturability. The inherent surface roughness and porosity complicate the fabrication of devices on paper, especially when their size is reduced. However, there are paper processing methods that can significantly improve the properties of its surface . For exaIn addition, the large pore size in the paper results in poor thermal performance . MoreoveOngoing research also shows that paper substrates cannot replace plastic ones in all devices. But, in specific applications, paper substrates can undoubtedly find applications. For example, the high porosity of the paper makes it possible to incorporate materials that have properties that are important for sensor applications, but which are difficult to fix on plastic substrates. In addition, continuous pore channels, allowing for efficient diffusion of gaseous molecules throughout the film matrix, provide maximal exposure of sensing material to the gaseous analytes and thus makes it possible to enhance the sensor signal and accuracy .Yao et al. , Hu et a® cellulose range, Maidstone, UK) is most suitable for developing microfluidic sensors due to its wicking ability [® filter papers is popular due to the choice of paper with the required porosity (pore size of 11–25 µm) to control particle retention and flow rates [® filter papers, flow rate, and particle retention, this paper is suitable for fabricating electrochemical devices capable of storing the reagents, filtering the sample, enabling reactions to occur, and flowing the detectable product towards the electrochemical testing area [As we can see, there are a variety of paper materials available to the user. However, it cannot be said that paper of all types is a universal material suitable for all applications. Different types of paper have different properties and therefore the choice is based mainly on the fabrication steps required in developing a device and also on the specific application area ,145,146. ability . The ranow rates ,149. Theing area . Paper ting area ,152.Nitrocellulose, obtained from the partial nitration of cellulose, enhances the porous property of cellulose and changes the material from hydrophilic to hydrophobic due to the presence of nitro groups. It has smaller pores than those of Whatman Grade 1 paper. Nitrocellulose membranes exhibit a high degree of non-specific binding towards biomolecules and are suitable for immobilization of enzymes, proteins and DNA ,153. In We must not also forget about office paper. The structure of office paper can be used in various configurations. For example, due to the non-degradability and relatively smooth surface of glossy paper, it is a good substitute for filter paper especially when modifying nanomaterials onto a surface rather than within the fibre matrix is necessary . In addiConventional paper is known to have disadvantages such as optical opacity, high surface roughness, and low mechanical strength and low stability in aqueous media, which may hinder further development of paper-based sensor devices for special applications ,156. On In addition to the examples above, unusual paper substrates such as carbon fiber paper (CFP) and paper hybrids can be found in paper-based sensor designs. Carbon fiber paper is a composite paper composed of carbon fibers and polymeric carbon. Its production process begins with polymerization and carbon fiber formation, followed by carbonization, papermaking, resin impregnation, molding, and a final heat treatment step . CFP hasA discussion of the advantages of certain types of paper for the development of flexible devices can be found in published reviews. In particular, Liu et al.  summarizAs follows from this consideration, the mechanical, chemical and electrophysical properties of each paper type differ from each other due to differences in the material composition and manufacturing processes. As a result, it is hard to generalize a set of properties for paper as the constituents of paper vary among different types of paper . For exaIn terms of device architecture, the humidity sensor comprises a sensing/transduction layer over a substrate with electrodes placed for physical interfacing. As a rule, paper-based humidity sensors are developed in two modifications that differ in their sensing mechanisms. These are capacitive and resistive. There are also impedance-based humidity sensors, but they are much less common. Other humidity sensors that show responses at different frequencies like quartz crystal microbalance (QCM) , surfaceThe most common way to manufacture paper-based (PB) humidity sensors is to apply a humidity-sensitive material to the surface of a paper substrate. It is assumed that the paper in such a sensor is a passive element, and the sensor performances are controlled by humidity-sensitive material. It is clear that not every material can play the role of humidity-sensitive material in paper-based humidity sensors.According to ,25,173, Carbon materials have been extensively studied as humidity-sensitive materials for flexible devices due to their high surface area, low toxicity, high electron mobility, mechanical compliance and good chemical stability . Graphen2, VS2, WS2, ZnIn2S4, and CdS in humidity sensing are their rich hydrophilic surface sites, which allow the occurrence of proton transition induced by the absorbed water molecules as long as the humidity level is increased. Additionally, due to the ultrathin 2D layered semiconductors, it is possible to create transparent humidity sensors.The common advantages of sulfide-based nanomaterials like MoSLike metal sulfides, nanomaterials based on metal oxides also have hydrophilic properties necessary for use in humidity sensors . Nanomat2 [Polymers is another group of materials widely used in the manufacture of humidity sensors . Polymer2 . The hum2 .Humidity sensing properties of materials used for humidity sensor fabrication are discussed in sufficient detail in ,197,198.As it was indicated before, the paper begins to degrade at temperatures above 100 °C, placing severe limitations on the quality of crystalline semiconductors that can be grown directly on the paper. Therefore, in many cases, developers prefer to use a polymer and carbon-based materials as sensing material. However, it is known that polymer- and carbon-based humidity sensors have limitations in many applications. For resolving above problem with deposition of crystalline material, three various approaches for overcoming temperature restriction have been proposed . The firThe roughness and porosity of the papers tend to hamper the performance of some electronic devices such as transistors and diodes; on the contrary, the roughness and porosity are attractive here because they increase the contact area with the ambient air and promote the adhesion to sensing materials used. Similar to the methods of forming sensitive material on polymer flexible substrates, the main methods of applying sensitive materials used in the fabrication of PB humidity sensors include handwriting ,180,208,It is clear that when designing flexible humidity sensors, developers very often fail to strike a balance between humidity sensitivity and response/recovery rate due to inherent properties of the materials used. Therefore, various strategies have been developed to optimize performances of humidity sensors, such as chemical treatment, alloying, transition to nanocomposites, structural engineering, Joule heating, etc. ,216,217.The main process that determines the sensory response to moisture is the adsorption of water vapor on the surface of the active material. Adsorption processes of water vapour taking place in porous media usually is described by an adsorption isotherm ,220,221.In porous materials used in humidity sensors, such as paper, the adsorption isotherms are almost exclusively of type II, i.e., with an S-shape ,223. TypIt is important to take into account that at desorption, we sometimes get a different dependence of the water content on the relative humidity than at adsorption . The desA is the resistivity at zero moisture content and B is a factor which reflects the sensitivity of the paper resistivity to the moisture content or to the RH at which the paper was conditioned. Since the ionic conductivity of the paper is proportional to the amount of water adsorbed on the surface of the cellulose fibers, then such properties of paper made it possible to use it as a humidity-sensitive material for the manufacture of PB humidity sensors [It is important to note that the properties of paper make it possible to use it not only as a substrate in the development of humidity sensors, but also as an active humidity sensitive material. The experiment showed that the paper has a hydrophilic surface. In brief, cellulose paper has a large amount of hydrophilic –OH groups that can adsorb water molecules. At low relative humidity, only a small amount of water molecules is absorbed by -OH groups via hydrogen bonds, resulting in a slight increase in paper conductivity . At high sensors ,232,233.Studies have shown that humidity sensitive properties of the paper can be improved by surface and bulk modification and functionalization ,166. ForAs mentioned earlier, the dielectric properties of paper also change when water vapor is adsorbed , which mWith regard to moisture transport in the paper, as a result of the studies carried out, it was concluded see  that moi−8 m2/s to 5.4 × 10−6 m2/s, which means that the diffusion of water vapour through the paper/pulp grades is reduced by between 5 and 1400 times compared with the diffusion of water vapour in air. The highest value for effective vapour diffisivity was found in the filter paper, and the lowest value in the lightweight coated (LWC) paper, which had been coated and calendered.One of the results of the conducted research is the establishment of a direct correspondence between water vapor diffisivity and the paper density. The effective water vapor diffisivities measured for different types of paper are shown in r and ε0 are the relative and vacuum permittivity constants, respectively, A is the plate surface area, and d is the plate distance. It can be seen from this equation that there are only three ways to change the capacitance of this device: (1) change the distance d between the two plates, (2) change the overlap area A between the two plates, and (3) change the dielectric permittivity of the material between the plates. This means that capacitive sensors can detect only those gases and vapours that affect these parameters. Water vapour can exert such influence and therefore by measuring the change in the capacitance, the presence of the water vapours in the air can be detected. In particular, if we take into account that the dielectric constant of water is 80, and paper, depending on the type, lies in the range of 2–4, it will be clear that the adsorption of water can lead to a significant change in the dielectric constant of the paper. In comparison, polymers have a dielectric constant of 3–6, metal oxides have a dielectric constant of 3.6–9, and carbon-based materials have a dielectric constant that varies between 6–15. It is clear that the lower the dielectric constant of the dielectric used and the greater the proportion of the space between the electrodes is occupied by water, the greater will be the effect, which is manifested in increasing the capacitance. In other words, high adsorption capacity and high porosity, which can be filled with water, are important parameters for materials suitable for the development of capacitive humidity sensors.Capacitive sensors are the most commonly used humidity sensors and have the advantage of being quick and simple to react to humidity. Capacitive sensors are linear and can operate over a wide humidity range. In addition, capacitive sensors are less sensitive to bending strain and temperature. In the simplest case, a capacitive-type sensor consists of two parallel plates. In such a structure, the capacitance between two electrodes is given by the Equation (2):γ is the surface tension of vapour in the liquid phase, MV is molecular volume, θ is contact angle, and ρ is the density of vapour in the liquid phase. Equation (3) was obtained for case of cylindrical pores [Kr, the Kelvin radius, and under a constant water vapour pressure or relative humidity. The smaller Kr or the lower the temperature, the easier capillary condensation occurs, i.e., at lower air humidity, free water is formed in the pores of the dielectric.It is important to note that for a noticeable change in capacitance, water in a dielectric material must be in a free state, since only free water molecules have dielectric properties close to those of liquid water, while bound water exhibits dielectric properties characteristic of ice. According to Evans  and Matzal pores . Thus, tConsidering that condensed water has the maximum effect on the capacitance, it becomes obvious that it is the pore size and porosity of the humidity-sensitive material that determine the sensitivity of the capacitive humidity sensor. The smaller the pore size is, the lower is the sensitivity threshold, i.e., at a lower humidity level, capillary condensation and an increase in capacity begin. At that, the greater the porosity and open pores volume are, the greater is the amount of condensed water and the greater is the range of capacity change when interacting with water vapour. It is important to note that capillary condensation can occur in all humidity sensitive materials used in the manufacture of humidity sensors, which by definition must be porous. These include paper, which has a porous structure with pore sizes varied from 0.7 nm to 8 µm. However, it should be borne in mind that the reduction of pore diameter will influence simultaneously the kinetics and hysteresis of sensor response, i.e., the response time and the magnitude of hysteresis will increase.A change in capacitance associated with a change in the distance between the electrodes is also possible if the interaction with water vapor is accompanied by a swelling effect. This effect in cellulose paper was observed by Olejnik et al. . HoweverIn reality there is a balance between the forces of retraction and the tendency for the chains to swell to infinite dilution. The degree of cross-linking has a direct effect on the level of swelling of the polymer and the strength of the network, i.e., increased cross-link density = decreased swelling capacity. This means that the swelling effect has strong dependence on the technology of polymer synthesis. Regarding a swelling rate, experimental studies have shown that for a rapid effect, the polymer should be a macro-porous (the large pores with size in the range of 0.1–1 μm), or even super-porous, i.e., along with high porosity, polymer should have interconnected open-cell structure . In thisOne should note that, the position and the shape of an adsorption isotherm, shown in previous section, strongly depend on the temperature . At highIn classical capacitive sensors a humidity sensitive material is placed between two, the top and bottom, electrodes see a. This iHowever, the experiment showed that when using the configuration of a plane-parallel capacitor, certain technological difficulties arise for the implementation of PB humidity sensors with better sensor characteristics. To achieve the maximum capacitive response to humidity and reduce the effect of parasitic capacitance, the thickness of the sensitive layer should be minimal, and the area of the upper electrode occupied by the conductive material should be maximum, since this area determines the capacitance value. A minimum sensing layer thickness is also required for fast response. But the requirement for fast response contradicts the requirement for increasing the area of the electrodes. This is due to the fact that the diffusion of water vapor under the top electrodes is in most cases the phenomenon that determines the response rate. If water diffuses rapidly into the thin sensing layer from the surface to the bottom electrode, then in metal plated areas water diffuses sideways under the top electrodes, and this diffusion rate can be quite low. In other words, sensitivity and response time are inversely related: if the structure is optimized for faster response, then the sensitivity will decrease, and vice versa. Therefore, the choice of the optimal structure is a compromise between these requirements.As a result of the research, we came to the conclusion that the configuration of planar sensor, when both electrodes are in the same plane b, is betAs a result of testing the capacitance-type IDE sensors, it was concluded that achieving the maximum signal requires a certain ratio between the thickness of the sensitive material and the IDE geometry, since the electrodes’ periodicity and the thickness of the sensitive coating layer impact the response of a capacitance-type IDE sensor ,261. In The humidity measurement in resistive sensors is based on the change in resistance or conductivity of a humidity-sensitive film produced by contact of humidity sensitive material with water vapor. The presence of water vapor modifies the electrical conductivity (or conductance) of the sensing layer by phenomena such as adsorption, chemical reactions, diffusion, and swelling (in the case of polymers) that occur on the surface or in the bulk of the sensing layer. This modulation may be quantified as a change in current, resistance or conductivity that are proportional to the water vapor concentration in the surrounding environment .In principle, the basic mechanism of conductivity in the majority flexible humidity sensors can be explained by the Grotthuss reaction, which is usually simplified as a proton-hopping process . It usuaMeasurements in resistive sensors are usually carried out with a constant voltage applied to the electrodes. It is important to note that, just like in capacitive humidity sensors, the ID electrode configuration is the most optimal when manufacturing resistive humidity sensors.Impedance humidity sensors are a type of devices that operate on the basis of a change in impedance. A sinusoidal voltage is applied to the humidity sensor in the frequency domain from subhertz to megahertz, and the impedance is calculated by measuring the current. The advantage of this type of humidity sensors is that they can accurately detect relatively low humidity. But, as a rule, this requires professional high-performance impedance spectroscopy. Despite the relative complexity of the measurement process, studies have shown that this method not only allows one to estimate the level of humidity, but also provides useful information about the mechanism of interaction of water vapor with the material .Typically, impedance-based humidity sensors are configured identically to resistive sensors. Since measurements in impedance-based humidity sensors are carried out on alternating current, detectable changes in impedance are the result of changes in both capacitance and resistance of the sensing element . GeneralTypical the complex impedance plots (CIPs) of paper-based humidity sensor without additional humidity-sensing element is shown in Paper is fundamentally different from the substrates used in the production of classical microelectronic devices. Therefore, the technologies used in conventional Si technologies are not applicable or have significant limitations for use in the manufacture of paper-based detector. This means that the development of paper-based devices requires new approaches and new technologies.2 laser scribing process to pattern nanostructured electrodes on paper, providing a green solution for reagentless mass-scale production.Given the scope of paper devices, in their manufacture, it is necessary to search for technologies and materials that meet the criteria of low cost, simplicity and efficiency of the production process ,266. TecWith respect to photolithography commonly used in microelectronics, there is a possibility of damage to the photoresist when paper is bent or folded when photolithography is used to make paper-based sensors. To overcome the problem associated with photolithography, Bruzewicz et al.  proposedAs for the description of patterning technologies listed in Electrodes play an important role in humidity sensors, especially those of the resistive type. The resistance of the electrodes should be as low as possible. Therefore, for their manufacture it is necessary to use highly conductive materials. For example, Arena et al.  used intMetallic particle inks offer the highest level of conductivity. To obtain a high level of conductivity, an additional post treatment of annealing  is usually required. This leads to the formation of a continuous interconnected phase between the metallic particles after the elimination of all the insulating components present in the ink . Silver is the most widely used metal so far owing to its high bulk conductivity and high resistance to oxidation. As a result, Ag nanoparticle inks have excellent low electrical resistance, when they are printed and cured on paper substrates. Most of the conductive silver inks are based on spherical nanoparticles or flakes. These inks exhibit a high conductivity but the obtained printed tracks and layers are usually opaque and brittle.Carbon-based materials such as carbon nanotubes (CNTs), graphite and graphene are another group of materials successfully used to make electrodes on the surface of paper. For example, Hu et al.  fabricatIn some publications, conductive polymers such as poly (PEDOT)  or polyaAs with conventional substrates, a variety of methods can be used to fabricate paper-based electrodes . For exaThe limitations of inkjet printing are especially due to the specific ink physicochemical properties requirements for allowing droplet ejection and the restriction in the particle size (<1 μm) for avoiding nozzle clogging . In thesIt was also found that in the manufacture of silver contacts, post-treatment drying at room temperature of about 25 °C followed by treatment at T ~ 150 °C is necessary to achieve maximum conductivity. At that only less than 2 min of drying time at this temperature was required to achieve the best electrical conductivity . It was Experiment has shown that besides surface pre-treatment and post-deposition thermal treatment ,295, theHand painting is also a frequently used electrode preparation method. Liu et al.  drew conWith regard to the stability of Ag-based contacts, studies by Liu et al.  showed tBenefiting from the rough surface of the paper, the electrodes of PB sensors can be prepared by simple, low-cost and solvent-free processing methods such as pencil drawing ,299,300.Therefore, in a number of publications, another simple approach to the manufacture of paper-based electrodes has been proposed. This approach was based on the use of conductive adhesive tapes ,175,178.2-laser writing of electrodes onto TEMPO-oxidized cellulose paper [9 Ω sq−1, the laser-irradiated area had a surface resistance of 108–102 Ω sq−1, depending on the laser power. The CO2-laser-induced carbonization of polymeric materials can be attributed to the generation of thermal energy due to the photothermal effect derived from their lattice vibrations [2-laser irradiation, the polymeric material reaches a high temperature, which causes chemical bonds such as C–O and C=O within the polymer to break and rearrange to form a graphitic structure (2-laser-irradiation process is extremely attractive for industrial use because it can be entirely performed in ambient air without any reagents.Some developers believe that it is not economically feasible to use noble metals in paper sensors, as they are expensive and non-renewable ones. To solve this problem, a method was proposed for forming conductive electrodes using the direct COse paper . As it ibrations . When sutructure . This apIf electrodes are required that are conductive over the whole area of the paper, then commercially available carbon paper can be used for this purpose, or metals, such as Au, can be deposited on the whole area of the paper. Another possibility to achieve this goal is to pyrolyze the paper by heating it to ~900–1000 °C in an inert atmosphere. However, the resulting material is rather brittle . It was Additional information regarding the formation of electrodes on paper can be found in the reviews by Cummins and Desmulliez , Hoeng eThus, we considered the possibilities of using paper for the development of humidity sensors and showed that paper is indeed a promising material for these applications, not only as a substrate, but also as a humidity-sensitive material. The review showed that all types of humidity sensors, including capacitive, resistive and impedance, can be developed based on the paper, and all types of humidity-sensitive materials such as carbon-based materials, solid state materials and polymers, can be used in these sensors. At that PB humidity sensors can be highly efficient in humidity monitoring. However, to achieve maximum sensitivity, the properties of the humidity sensitive materials used in PB sensors must be optimized. The analysis also showed that printing technologies are the most suitable for the formation of both a sensitive layer and electrodes on a paper substrate. In the second part of this review, “Humidity sensors performances”, we will already consider the specific approaches used to manufacture such paper-based humidity sensors. In conclusion, we will analyze the problems that need to be solved in order to promote paper-based humidity sensors on the sensor market and discuss the current trends in their development.


Organophosphate insecticides with broad spectrum and high efficiency make a great difference to agricultural production. The correct utilization and residue of pesticides have always been important issues of concern, and residual pesticides can accumulate and pass through the environment and food cycle, resulting in safety and health hazards to humans and animals. In particular, current detection methods are often characterized by complex operations or low sensitivity. Fortunately, using monolayer graphene as the sensing interface, the designed graphene-based metamaterial biosensor working in the 0–1 THz frequency range can achieve highly sensitive detection characterized by spectral amplitude changes. Meanwhile, the proposed biosensor has the advantages of easy operation, low cost, and quick detection. Taking phosalone as an example, its molecules can move the Fermi level of graphene with π–π stacking, and the lowest concentration of detection in this experiment is 0.01 μg/mL. This metamaterial biosensor has great potential in detecting trace pesticides, and its application in food hygiene and medicine can provide better detection services. Currently, there are many types of pesticides in the world, and the application of pesticides has brought considerable economic benefits to agriculture. However, the excessive utilization of pesticides has produced a serious influence on human health and the ecological environment. Taking organophosphate pesticides as an example, they are toxic to insects and mammals, and can easily damage their nervous systems . In addiTraditionally, detection methods for pesticide residues include high-performance liquid chromatography, gas chromatography, and liquid chromatography–tandem mass spectrometry. Although these methods have high sensitivity, their expensive equipment, stringent experimental conditions, and long experimental time limit their applications ,6,7,8,9.Metamaterials, composed of sub-wavelength periodic unit cells, can produce abundant electromagnetic responses in the visible, terahertz, and infrared regions ,11,12. BTraditionally, metamaterial sensors consist of a dielectric layer and a metal layer, and they are sensitive to the refractive index of the top layer of the analyte. For example, a metamaterial sensor can measure 4-methylimidazole at concentrations from 0 to 20 mg/L, and the excited local electric fields effectively enhance the interaction between the incident terahertz light and the matter under testing . By usinIn this work, a graphene-based metamaterial biosensor working in the terahertz band is proposed. The sensor is composed of a polyimide (PI) film as the dielectric layer, an aluminum structure array as the metal layer, and monolayer graphene as the sensing interface. Simulation results indicate that the monolayer graphene, with varying Fermi levels, can modulate the entire electric field and produce the phenomenon of amplitude change. In addition, the adjustable amplitude range of the graphene-based metamaterial biosensor is almost independent of the structural parameters. Using phosalone as an example, the increasing concentration of the analyte results in a rise of the Fermi level of graphene, showing an increase in the transmission amplitude. The limit of detection (LOD) achieved in this experiment is 0.01 μg/mL. These findings demonstrate the potential of graphene-based metamaterial biosensors for trace detection of residual pesticides, and they may also be applied for detection devices in food hygiene and medical fields.x = Py = 150 μm, and a square ring with an outer length of L1 = 122 μm and an inner length of L2 = 90 μm. The conductivity of the aluminum material is σ = 3.56 × 107 Sm−1 [z-axis, with the electric field direction along the positive direction of the x-axis. The unit cell boundary condition was utilized both in the X and Y directions, and the open boundary was utilized in the Z direction to achieve a perfect absorption boundary.The proposed model of the graphene-based metamaterial biosensor is depicted in 107 Sm−1 . Polyimi107 Sm−1 . Prior tF ranging from 0.01 eV to 0.04 eV are analyzed. As the Fermi level of graphene increases, the amplitude at the resonance frequency gradually rises, indicating that the resonance becomes weaker. The effective conductivity of the biosensor also increases as the Fermi level rises, which is the main reason for the weaker resonance. As shown in F from 0.01 eV to 0.04 eV, the change in transmission amplitude ΔT and ΔEF exhibit a good linear relationship with a fitting degree of R2 = 0.99, which is beneficial for the following detection of substances.The designed biosensor operates by detecting changes in the Fermi level of the graphene induced by the analyte, which in turn causes changes in the resonance strength ,33. In tIn addition, the surface electric fields on the top layer of the biosensor at the Fermi level of 0.10–0.14 eV are studied. As shown in 1 and L2, respectively) of the aluminum rings are selected as key parameters, and different spectra are analyzed. The change in transmission amplitude (ΔT) is set as the difference in amplitude when the Fermi energy level (ΔEF) changes. The larger the value of ΔT, the more sensitive the sensor is to changes in the Fermi level of graphene. Therefore, the influence of the structural parameters on the dynamic range of amplitude can show the change in sensitivity.The structural parameters of the graphene-based metamaterial biosensor determine the intensity of the electromagnetic field that can be excited in the aluminum ring array layer. This, in turn, affects the range of transmission amplitude that can be controlled by the monolayer graphene. To investigate this effect, the outer and inner side lengths  in the frequency range of 0.3 to 0.8 THz. As shown in The monolayer graphene used in this experiment was purchased from Jicang-Nano Technology Co., Ltd.  with a size of 10 × 10 mmA standard solution of 10 μg/mL phosalone was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China. This standard solution was diluted with acetone to prepare phosalone solutions with concentrations of 0.01 μg/mL, 0.05 μg/mL, 0.1 μg/mL, 1 μg/mL, and 2 μg/mL. These solutions were then applied on the surface of the biosensor for detection. Due to the fast evaporation rate of acetone, heating is not necessary during the drying process.i/T0, where Ti and T0 represent the transmission amplitude at the resonance frequency in the i-th concentration and zero concentration of the analyte, respectively. After extracting the experimental data, ΔTi/T0 for phosalone solution concentrations of 0 μg/mL, 0.01 μg/mL, 0.05 μg/mL, 0.1 μg/mL, 1 μg/mL, and 2 μg/mL corresponds to 0%, 1.92%, 9.37%, 11.32%, 13.73%, and 13.69%, respectively.A pipette was used to drop 20 μL of phosalone solution onto the surface of the biosensor. As the solvent acetone quickly evaporates, the detection time is greatly reduced. Different spectral curves were obtained at different concentrations, as shown in i/T0 increases rapidly and appears to maintain a linear relationship with the concentration of the solution. As concentrations further increase, ΔTi/T0 remains almost unchanged and exhibits a clear saturation effect. Therefore, the relative change in transmission amplitude caused by increasing solution concentrations is not a simple linear trend, which is common in biological sensing. To characterize the binding ability between the monolayer graphene interface and small biological molecules such as phosalone, the Hill model can be employed to fit the experimental data. The description of the Hill equation is as follows [max is the maximum ΔTi/T0 value at the saturation concentration, c is the concentration of the phosalone solution, n is the Hill coefficient, and k is the dissociation constant. The calculation can be performed using the commercial software Origin. The values of the parameters in Equation (1) were obtained by selecting the Hill function for fitting in the software Origin, and then the parameters were determined through the Levenberg–Marquardt iterative algorithm. The calculated Vmax is 0.136, the Hill coefficient n is 1.558, the dissociation constant k is 0.032 μg/mL, and the goodness of fit is 0.999. The consistency between the experimental data and the fitting curve reflects the reliability and accuracy of the results.The relative change in transmission amplitude is presented in  follows :(1)y=VmaThe designed biosensor offers several advantages over traditional pesticide detection methods, such as low cost, ease of operation, and extremely short detection time. Moreover, it is more appropriate for biosensing at trace concentrations than traditional dielectric-metal metamaterials.As shown in A graphene-based metamaterial sensor characterized by spectral amplitude changes is proposed. Taking the phosalone in organophosphorus insecticides as an example, the designed sensor has been simulated and experimentally verified. In the entire sensor structure, the PI film serves as the dielectric layer and the aluminum structure array acts as the metal layer, reducing cost. The monolayer graphene as the sensing interface further enhances the interaction between the surface and the analyte. The structural parameters of the metal layer do not significantly affect the adjustable amplitude range of graphene within a small variation range. Graphene can interact with molecules through π–π stacking, and graphene at different Fermi levels affects the electric field strength that can be excited by the entire metamaterial. Finally, the lowest concentration of detection LOD is 0.01 μg/mL, and the amplitude change in the concentration range of 0–2 μg/mL is in line with the Hill model. The graphene-based metamaterial biosensor has the advantages of a small size, high sensitivity, and label-free detection, making it a promising detection method for food safety industry applications.