And also, low-cost epoxy resin (ER) proved the great feasibility of fabricating these devices using the CO2 laser ablation technique in our previous studies. However, such a technique has shown negative impacts on such ER-based microfluidics as rough surface microchannels, and thermal defects. Therefore, incorporating different proportions of boric acid (BA) into epoxy resin formulation was proposed to obviate the genesis of these drawbacks in ER-based microfluidics. The structural and optical properties of plain ER- and B-doped ER-based chips were characterized by Fourier transform infrared (FT-IR) and UV/Vis spectral analyses. Furthermore, their thermal properties were studied by thermo-gravimetric (TGA) and differential scanning calorimetric (DSC) analysis. A CO2 laser ablation machine was used in vector mode to draw the designed micro-channel pattern onto plain ER- and B-doped ER-based chips. The quality of microchannels engraved onto these chips was assessed using 3D laser microscopy. This microscopic examination showed a noticeable reduction in the surface roughness and negligible bulge heights in the laser-ablated micro-channels. On the other hand, overall and specific migration using gravimetric methods and gas chromatography-mass spectrometry (GC–MS), respectively, and PCR compatibility test were performed to explore the convenience of these micro-plates for the biological reactions. These findings validated the applicability of B-doped ER-based microfluidics in bio-analytical applications as a result of the effective role of boric acid in enhancing the thermal properties of these chips leading to get micro-channels with higher quality with no effect on the biological reactions.CO Moreover, they are often considered lower costly compared with silicon/glass and easy to process with several fabrication methods. Currently, both thermoplastics and thermosets e.g., PDMS (polydimethylsiloxane)3, PMMA (polymethylmethacrylate)4, PC (polycarbonate)5, and PS (polystyrene)6 are widely employed in microfluidics.In the last ten years, polymers have replaced silicon/glass as alternate substrates for microfluidic devices because of the versatility in their chemical, optical, and physical properties7. Epoxy resin readily available in the marketplace has several crucial characteristics that make it a strong candidate for use in microfluidics, including a high young's modulus, high optical transparency, autoclavability, hydrophobicity, negligible migration, ease of handling, and low cost8. Concurrently, epoxy polymers exhibit low thermal stability and high flammability9.Epoxy resins are extensively used in industry as construction materials, coatings, adhesives, and matrices for advanced composites because of their superior mechanical and chemical resistance, electrical properties, and resistance to moisture10. In this context, fine powder of boric acid (particles dia. < 40 µm) was previously used as flame-retardant filler for epoxy resin (1–10% of ER mass). The thermal stability of the epoxy composite was increased with increasing amount of boric acid, and this enhancement was attributed to decrease mobility of epoxy phase in the vicinity of the boric acid particles and the more uniform distribution of boric acid in epoxy matrix11. On the other side, boron-containing compounds including boric acid have been also used as curing agents12. Similarly, BA has been utilized as a cross-linking agent for cellulose fibers/polyvinyl alcohol composite13, polyvinyl alcohol and ethyl cellulose films as drug delivery systems14, and polyvinyl alcohol adhesive15. The cross-linking capability for boric acid with such biodegradable hydrophilic polymers  was explained on the basis of the dispersion uniformity to a coulombic acid/base reaction of the acidic protons of the three –OH groups on this simple triprotic acid (boric acid) with the hydroxyl groups of the polymer molecules. The high reactivity of boric acid can be attributed to the presence of vacant d-orbital in trivalent boron atoms, which causes it to react rapidly with various nucleophiles to form complexes15. Likewise, monomeric and polymeric epoxy resins may also include reactive -OH groups, which arise from the ring-opening reaction of epoxides, reacting with boric acid to result in an additional cross-linking. As well as being examined as a curing accelerator to the embodiments that contain epoxy resin, curing agent, and catalyst where they cure more rapidly if contain a stoichiometric excess of boric acid compound over the catalyst16. Despite the mentioned above benefits of the incorporation of boric acid in an epoxy matrix, it may cause coloration of the microfluidic platforms with pale yellow color declining their transparency and subsequently reducing the quality of the latter17 because transparency considers one of the most critical quality peculiarities of microfluidic devices18.Boron compounds are relatively nontoxic, naturally available, ecofriendly and have proven to enhance the fire retardancy of epoxy polymers, wood, cellulose, cotton, etc. Amongst the boron compounds, boric acid is well known for its fire retardancy and exerts its flame retardant properties at a temperature well below the normal pyrolysis temperature of polymeric materials. As an inorganic reagent, boric acid shows relatively low toxicity2 laser ablation approach in our previous study. However, they have revealed a downside because the laser intensity applied in the micro-patterning led to defects by the action of the resulting heat as bulge heights and surface roughness8. Therefore, this work will address enhancing the thermal stability of ER-based microfluidic platforms with doping epoxy resin with boric acid. Regarding the significance of uniformity of the distribution of processing aids in the epoxy resin matrix in achieving the effective role20 and tuning the act of boric acid to enhance the thermal properties of the microfluidic devices with no negative impact on the other quality merits, before becoming a part of the composition, the boric acid is dissolved in methanol which a reactive diluent for the main component of the compositions (epoxy resin). Such methodology was proposed to enhance the boric acid distribution in the ER matrix and consequently, the thermal stability and micro-channel quality of the boric acid-doped epoxy resin (B-doped ER)-based microfluidic platforms with maintaining their transparency. Furthermore, the optimization of laser micromachining parameters such as laser power (P) and scanning speed (U) was studied. Further, other critical assessments on these boric acid-doped epoxy resin-based microfluidic platforms' are carried out to explore their convenience for biotechnological applications. These assessments involved the measurement of the potential migrants in addition to PCR compatibility testing.Otherwise, epoxy resin-based microfluidic devices have already shown good processability using the rapid and cost-effective CO3BO3, MW (g/mol) = 61.83 (Carlo Erba Reagents). Methanol HPLC grade MW = 32.04 from Fisher Scientific UK.Diglycidyl ether of bisphenol-A (DGEBA) with epoxy equivalent weight (EEW) = 185–190, and curing agent (hardener); modified cycloaliphatic polyamine were purchased from Green Build Chemical Company (Egypt). Boric acid, H21 with some modifications. Briefly, different proportions of boric acid were dissolved in methanol at room temperature to form a clear alcoholic solution of boric acid with various concentrations % (w/v), as in Table The fabrication method of pristine ER- and B-doped ER–based chips was taken place by compounding the components and casting technique adapted from the method of Lau and Lu2 laser micro-machining is an efficient and cost-effective method of producing a wide range of polymeric microfluidic devices22. The pre-fabricated epoxy resin cast chips (3 mm thick) were micro-machined using a commercial bench top CO2 laser  with a maximum power of 30W  spectral analysis. FTIR spectra were recorded for KBr discs on a Shimadzu FTIR-8400S spectrometer in a range of 400–4000 cmThe epoxy resin shows a transparent aspect in its pure state. To explore the impact of the incorporation of boric acid in the epoxy resin compositions on the optical properties of microfluidic plate, the transparency of the epoxy resin specimens was measured using UV/Vis spectrophotometer (Hitachi Model U-3900).Vickers hardness of epoxy resin plates was carried out using MICRO Hardness Tester Shimadzu (HMV-2 series), where test force (490.3 mN) which is equal to 0.0499 kgf load, was applied for 10 s. The hardness value HV was calculated from the indentation load and the diagonal of the Vickers imprint.The thermal stability of the epoxy resin specimens was assessed using Shimadzu TGA-50 thermogravimetric analyzer by heating the specimen from ambient temperature to 800 °C at a rate of 10 °C/min under a nitrogen atmosphere.The thermal transition in epoxy resin specimens were studied by differential scanning calorimetry (DSC) using a Discovery X3 DSC . The thermal behavior was studied under non-isothermal linear heating (10 °C /min) in a nitrogen atmosphere from room temperature to 800 °C.−1 starting from room temperature to 800 °C with nitrogen purge gas.Differential thermal analysis (DTA) was performed using a Discovery DTA . The analysis was performed at a heating rate of 10 °C min23. The autoclaving standability was evaluated by measuring their dimensions and weight accurately before and after autoclaving. For the pristine cured epoxy resin-based chips, it was found to withstand autoclaving as indicated in our previous study8. Herein, the autoclaving standability of the B-doped ER-based chips was assessed to explore the impact of the incorporation of boron compounds in the epoxy resin matrix.As well-known, all substrates and devices in biological applications which in contact with biological components, organs, or cells have to be sterilizable because their contamination could damage these biological systems and affect the accuracy and reproducibility of such analyses. Autoclaving is the most widely technique used for sterilization because of its efficiency and low cost. The capability of epoxy resin-based plates to withstand autoclaving was assessed by conducting a standard autoclaving with saturated steam at 121 °C under the pressure of approximately 15 pounds per square inch for 20 min using MaXterile 60 autoclave24. Concisely, a B-doped ER specimen was immersed in distilled water as a polar simulant or in dichloromethane as a low polar simulant and heated with shaking at 100 °C for 2 h. An aliquot of the aqueous simulant (2 ml) was then heated to evaporate the simulant and measure the overall migration by weighing the remaining solid  by using the sensitive balance. For measuring the specific migration, these solid residues were dissolved in methanol (2 ml), and the resulting methanolic solution was qualitatively analyzed by gas chromatography coupled with a mass spectrometer (Shimadzu GC-MS-QP2010).To guarantee the aptness of epoxy resin-based microfluidic devices for bio-analytical application, the non-presence of any substances that could interfere with the biological components is highly necessary for these analyses to ensure their accuracy and sensitivity. The potential release of the components from B-doped ER compositions was measured according to the method reported in a study by Cardama and his colleaguesThis test is performed to examine the effect of contacting a polymerase chain reaction (PCR) mixture on cured epoxy resin plates.2, optimized Dream Taq™ buffer, and dNTPs that save time and decrease contamination. It can cause robust amplification of genomic DNA (up to 6 kb). The entire length of the EGFR exon 19 gene was amplified using the oligonucleotide primers Ex19 Fw (5′-AGCATGTGGCACCATCTCAC-3′) and Ex19 Rv (5′-ATGAGAAAAGGTGGGCCTGA-3′). The reaction mixtures volume was 25 µl contained 0.1 ng of sample DNA, 12.5 µl 2 × PCR Fast Gene Taq 2 × Ready Mix , a 200 nM concentration of both primers, and 2.5 µl bovine serum albumin (BSA). BSA weight (1 µg/µl) dissolved in freshly prepared phosphate buffer saline (PBS) solution (pH 7.4)25. PCR cycling was performed in a Lab cycler  with the following parameters: one cycle of 4 min at 94 °C, followed by 35 cycles of denaturation for 1 min at 94 °C, annealing for 30 s at 58 °C, extension for 2 min at 72 °C and final extension at 72 °C for 5 minutes26. The reaction mixture was added to a PCR tube containing a piece of ER and ER coated with BSA to test its effect on the PCR test efficiency.The polymerase chain reaction (PCR) includes primer-mediated enzymatic amplification of DNA. This technique uses the ability of DNA polymerase to synthesize a new strand of DNA complementary to the template strand. PCR Master Mix (2X) is a pre-mixed solution containing Dream Taq™ DNA polymerase, MgClNucleic acid bands (PCR products) were identified and visualized by running in 1.0% agarose gel in 0.5 × TBE buffer system with 90 V for 35 min. in horizontal gel electrophoresis apparatus , followed by staining with ethidium bromide, a non-radioactive marker, and pictured on UV Trans illuminator, . Radiolabeled DNA fragment sizes were approximated using eco in Action (ready-to-use) 100 bp DNA Ladder (H3 RTU).−1 corresponding to the bending vibration of B–O–B. The band at 636 cm−1 is ascribed to the deformation vibration of B–O. The band at 1192 cm−1 is attributed to the in-plane bending vibrations of B–O–H. The band observed at 2263 cm−1 could be caused by stretching vibrations of atoms in the B–O bonds. The stretching vibrations of O–H are supported by the broad band at 3461 cm−1. The absorption band at 1385 cm−1 is belonging to asymmetric stretching vibrations of B–O28.FTIR is an analytical technique used to identify organic, polymeric, and, in some cases, inorganic materials. Each molecule or chemical structure will produce a unique spectral fingerprint, making FTIR analysis a great tool for chemical identification. FTIR spectra of boric acid, pristine ER, and ER doped with boron by incorporating varied proportions of boric acid in epoxy resin matrix were shown in Fig. −1 is due to overlapping the adsorption peaks belonging to the –NH2 vibration of amine compounds and stretching vibration of OH of epoxy resin. Adsorption peaks at 1605, 1580, 1510, 1455 cm−1 are assigned for Ar–C=C–H stretching vibrations. The absorption bands due the gem-dimethyl C (CH3)2 appeared at 1384 and 1360 cm−1 is. The two bands at 729 and 693 cm−1 may be attributed to out of plan bending of aromatic rings. The peak at 1182 cm−1 is due to C–O stretching of aromatic ring of DGEBA. The aliphatic –CH2 and –CH3 vibrations are seen in the region 3000- 2850 cm−1 for both the polyamine adducts. The absorption peaks appeared at 1036 and 1240 cm−1 is due to symmetric and asymmetric stretching vibrations of aromatic ether C–O–C). The disappearance of the peaks at 3056 and 915 cm−1 belonging to vibration of C–H and C–O of epoxy group, respectively, in addition to the appearance of the characteristic band due to C–N stretching vibrations at 1108 cm−1 indicating the opening of epoxy rings and confirming the curing process29.The prepared cured epoxy system was characterized by IR for to confirm its composition and crosslinking of polymeric epoxy resin Fig. . The cur−1 , 1607 and 1510 cm−1 (aromatic C=C stretching vibrations). The adsorption peak replicated at 1030 cm−1 with medium intensity as a result of overlapping the frequencies of C–O–C stretching with the corresponding due to B–O–C groups, which confirms the reaction between boric acid and epoxy resin30. However, this peak is 1030 cm−1), which already exists in the plain epoxy resin31. Also, absorption peaks with medium intensity occur at 1330–1375 cm−1 due to the stretching vibration of the B–O and B–N bonds.The spectra of ER containing boron additives exhibited characteristic broad absorption peaks at 3340 (O–H and N–H stretching vibrations), bimodal peaks at 2875 and 2931 cm−1) was observed with increasing the proportion of boric acid incorporated in the epoxy resin. These findings prove the reaction of the boron-containing species with the cured polymeric epoxy.In comparison with neat epoxy resin, the stretching vibration of O–H in the modified epoxy resin shifted to lower wavenumber region, in addition to a broadening of the hydroxyl group is attributed to the cross-linking reaction and formation of hydrogen bonds originated from reaction of the hydroxyl groups of cured epoxy resin and boron containing species. Moreover, the presence of systematic increases in boric acid concentrations resulted in increased intensity in frequencies associated with B–O and B–N stretching and the characteristic band due to stretching vibrations of C–N bond  is an essential characteristic of microfluidic devices, and it should exceed 90% to ensure good visability35.Hardness is well-defined as a material's ability to resist penetration, indentation, and abrasion. Vickers hardness values of plain ER and B-doped ER specimens were tabulated in Table 37, this study has aimed to enhance the thermal stability of ER substrate via compounding of epoxy resin with boric acid (flame retardant) into the resin matrix. Therefore, thermo-gravimetric analysis (TGA) has been used to assess the thermal stability of ER and B-doped ER specimens. TGA thermograms depicted the relationship between the weight losses owing to the thermal decomposition of specimens with temperature as shown in Fig. T5, T10, T20, T50, T70, and T90, respectively. The thermo-oxidative degradation of the plain epoxy resin was nearly completed at 790 °C, and the mass residue was ~ 1.75%. Therefore, the residues of B-doped ER specimens at 790 °C were used to evaluate their thermal stability. The data obtained from the TGA thermograms of the prepared epoxy resin compositions are given in Table Considering the thermal effect of the laser ablation procedure that may raise the treated substrate temperature to 150 °C maximum, as mentioned in several previous studiesThese findings exhibited that incorporating the boric acid in the epoxy resin compositions has an efficient role in the enhancement of the thermal stability of the boron-doped epoxy resin casted specimen. The degradation temperatures for such boron-modified epoxy resin specimens were higher than their counterpart of plain epoxy resin specimens. Increasing the proportions of boric acid employed in the fabrication process led to elevating.T5 and T10 of B-doped ER cast specimens prepared using 20% of BA was ~ 152 and ~ 268 °C, respectively, and higher than those corresponding for plain epoxy resin by 32 and 114 °C, respectively. The residue of the B-doped ER cast specimen (10% BA) at 800 °C is 7.5%, while the neat epoxy polymer almost decomposes completely.The degradation temperatures. 3BO3) into epoxy resin leads to a significant modification of the structure and properties of epoxy thermosets with increasing thermal stability of the modified resin. However, the compounding methodology applied in this study makes these structural and thermal changes seem to be highly complicated and inconclusive, where they can be caused directly by action of boric acid or the reactive boron-containing spices resulting from the interaction of methanol with the boric acid or indirectly by the interactions of boron-containing compounds with uncured or cured epoxy resin. H3BO3 eliminates water at a temperature higher than 100 °C. The water released during its decomposition reduces the temperature and can dilute the combustible gases in the combustion zone38. At higher temperatures, H3BO3 is converted to boric trioxide (B2O3) which can form a glassy film on the burning surface of the polymer, thus inhibiting the diffusion of flammable gases in the combustion zone and reducing the flame spread on the polymer surface7. On the other side, the potential intra-molecular B–N interactions that would form complexes such as 1,3,6,2-dioxazaborocanes (DOABs) (cross-linking), and formation a Lewis acid/base type products as well as hydrogen bonding, can also enhance the thermal stability of epoxy resins.The incorporation of boric acid (HTg) of plain and B-doped ER specimens prepared using varying BA proportions under non-isothermal linear heating (10 °C/min) from ambient temperature to 800 °C.Differential scanning calorimetry (DSC) was used to determine phase transition temperatures and glass transition temperature  is widely used to indicate the curing degree that depends on its chain flexibility, cross-linked structure, and intermolecular hydrogen bonding of the resin 40. However, Tmax indicates the speed of the curing process. Tg and Tmax of plain and boron-modified epoxy resin are tabulated in Table Tg), the inflection point of the curing exothermic peak, was increased with increasing the proportions of BA up to 15%. This increase in the glass transition temperatures can be explained by that the boron-containing compounds react with epoxy resin rather than the hardener (a higher degree of cross-linking). In this context, it has been previously reported that the glass transition temperature of thermosetting plastics such as epoxy resin shifts to higher temperatures at higher degrees of cross-linking41. Contrary to that, incorporating a higher amount of boric acid in the epoxy formulation led to a slight decrease in the Tg of the boron-doped epoxy resin specimen compared to the neat epoxy resin specimen. Similarly, the thermal decomposition process of boron–modified epoxy resin specimens has one stage as the pristine epoxy resin. The Tmax of plain epoxy resin was ~ 353 °C. t is found that the incorporation of BA up to 15% in epoxy resin increased Tmax by ca. 11 °C, in comparison with that of pure epoxy. The higher thermal stability might be because the BA incorporating increases the cross-link density of the epoxy. However, the Tmax was decreased by incorporating boric acid in the epoxy resin at a higher amount. This increase in the cross-linking density of these boron-modified epoxy resin specimens (5–15%) can be supported by increasing the hardness with increasing the amount of boric acid incorporated in the epoxy resin as mentioned above. This can be attributed to the homogenous distribution of boron-containing species because of the high miscibility of epoxy resins system components resulting in increasing the cross-linking density that can enhance the ductility of the polymer matrix. Notwithstanding, declining the cross-linking density at the highest BA concentration (20%) might be due to inhibition of the curing and subsequently lowering the cross-linking density.Glass transition temperature  reflect the high thermal stability of the polymer42. From these findings, it was indicated that the onset temperature of the second exothermic peak (Ton2) and the melting point of B-doped ER specimens were increased by increasing the concentration of the boric acid up to 15%. These results proved that incorporation of boric acid in the epoxy resin formulations enhance the thermal stability of the resin specimen.Differential thermal analysis (DTA) was conducted for plain ER and B-doped ER specimens to explore the characteristic exothermic peaks and measure the melting point. The DTA thermograms were demonstrated in Fig. 43. Due to the advantages of steam sterilization (autoclaving) including the high efficiency, ease of use, low cost, and no use of toxic compounds44, B-doped ER-based microfluidic platform (prepared from a composition containing 10% BA) was sterilized in an autoclave at 121 °C for 20 min under the pressure of 2 atm. as performed on the plain epoxy resin-based microfluidic plate in our previous study for assessing the serviceability of these micro-plates based on the modified epoxy resin under autoclaving conditions with the comparison with plain ER-based ones. The gross weight the fabricated B-doped ER micro-plate and dimensions, and surface roughness of the micro-plate and their micro-channels were measured and the data of these trails are tabulated in Tables Sterilization of the microfluidic devices utilized in most biological applications such as organs-on-chips employed in biomedical applications is a crucial process to avoid contamination which can affect the validity of experiments and the accuracy of the results. Hence, the ability of these devices to endure such a sterilization process is a key property in these applications45. Therefore, determination of the overall and specific migration is so essential. Regarding the polar solutions of PCR and the high denaturation temperature of PCR (95 °C), migration testing has been conducted using distilled water as a stimulant at 100 °C46. The overall migration of the B-doped ER specimen in polar simulant (water) was less than 0.1 mg dm−2. The GC–MS chromatogram is shown in Fig. −2. This less polar simulant exhibited higher potency for occurring migration than the more polar counterpart (distilled water). In the GC–MS chromatogram ram Fig. b, the mi47. PCR inhibition can also occur by inhibitory components that may leach from the substrate of the microfluidic device into the PCR mixture48. The compatibility of the materials employed in microfluidic fabrication with PCR has to be addressed as an urgent issue. The PCR compatibility with B-doped ER-based chips was assessed and the results were listed in Table 48. Herein, the incorporation of BSA or coating of B-doped ER-based chips with BSA was tried. The compatibility assessment results of B-doped ER-based chips with PCR after these treatments -based microchips22. Further, increasing the boric acid concentration increased the micro-channel width. The micro-channel was depicted with the highest width by high-output lasers moving slowly i.e., at 3.6 W and 5 mm/s. Whereas the highest micro-channel width on the plain epoxy resin (~ 135.91 μm) was recorded at a scanning speed of 5 mm/s and laser power of 3.6 W. So, the highest micro-channel width on B-doped ER chips (20% boric acid) (~ 155.53 μm) obtained at the same processing parameters. Hence, compared to direct parameters, the composed parameter, laser output power over moving speed (P/U), may have a greater impact on micro-channel width  was obtained at a laser power of 3.6 W and a scanning speed of 10 mm/s for microchips prepared by 5% boric acid in the epoxy composition. Meanwhile, at 1.8 W and 15 mm/s, the lowest micro-channel depth of about 20.25 m was recorded for microchips prepared by incorporating 20% of boric acid in the epoxy composition. The relationship between P/U and micro-channel depth was plotted and displayed in Fig. The impact of laser input parameters and boric acid concentration on the micro-channel depth is demonstrated in Fig. 51. Figure The product of dividing micro-channel depth by micro-channel width is defined as the aspect ratio. A high aspect ratio of a micro-channel is considered a key feature in the technical feasibility of microfluidic chips, particularly in life science, to combine cell screening action with high fluidic throughput in continuous flow systemsRa) was chosen as a measure of surface roughness because it is the average arithmetic height of surface irregularities  from the mean line along the scanning length at the bottom of the micro-channel52. The influence of input power, scanning speed, and BA concentration incorporated into ER matrix on the Ra of the micro-channel surface is shown in Fig. Ra, increased with raising the laser power. However, it decreased by increasing the scanning speed. The highest roughness ~ 29.5 μm was recorded at a laser power of 2.4 W and a high scanning speed of 10 mm/s for ER-based chips. However, the lowest Ra (~ 1.88 μm) was recorded at laser power of 1.8 W and scanning speed of 20 mm/s for B-doped ER-based chips prepared using 15% boric acid.The roughness of the micro-channels surface is a crucial issue for its high impact on fluid flow and the efficiency of the microfluidic devices. The arithmetic average of roughness (53. Considering the impact of the composed parameter (P/U) that ranged from 0.35 to 0.75 on the roughness, it was indicated that by increasing P/U from 0.35 to 0.6, a slight increase in Ra. However, at higher P/U, a pronounced increase was observed. The 3D micrographs for plain ER- and B-doped ER-based specimens were given in At a scanning speed of 5 mm/s, no noticeable difference was recorded in the resulting surface roughness of micro-channel drawn over B-doped ER-based chips prepared with varying proportions of boric acid. The impact of boric acid concentration tends to be more pronounced at higher scanning speeds (> 5 mm/s) since the micro-channel surface roughness was reduced by increasing the boric acid concentration. These findings agree with those reported in a previous study that indicated that the roughness of the cut increased with decreasing laser scanning speeds54. However, the last type cannot be removed and can induce cracks in the following processes.The bulges on the rim of a micro-channel can be formed by two mechanisms. One is called the 'conventional bulge' caused by molten polymer re-solidification in a cool-air atmosphere. The other is referred to as a "hump" because of thermal distortion caused by thermal stress or residual stress in a large temperature gradient that forms on the rim of the micro-channel. Coating the microfluidic platform with PDMS or an unexposed JSR layer can eliminate the first type55.The influence of laser ablation parameters and the amount of boric acid on the bulge height was investigated. The results are shown in Fig. 3BO3 after its dissolution in methanol into the epoxy resin matrix at different concentrations. Incorporation of BA was performed with the proposed to enhance the thermal stability of microfluidic substrate, and consequently, the dimension stability and quality of microfluidic micro-channels. The structural, physical, and thermal properties of the modified epoxy resin specimens were studied using FTIR and UV/Vis spectral analyses and mechanical testing, TGA, DSC, and DTA, and compared to those of the control unmodified (neat) epoxy resin specimen. Based on the finding of these studies, it was concluded that the mechanical and thermal stability of epoxy resin were noticeably improved via the acting of boron compounds formed and present in an epoxy matrix as a sintering and fluxing agent and simultaneous formation of DOPO derivatives and other potential interactions between ER and boron compounds. These improvements were fulfilled with a negligible effect on the optical transmittance of the epoxy resin chips. CO2 laser micro-machining has been operated using laser power in a range of 1.8–3.6W and scanning speed in the range of 5–20 mm/s to optimize the processing parameter of boron-doped epoxy resin and exploring the impact of the incorporation of boric acid in epoxy polymer compositions on the dimension and quality of engraved micro-channels. The findings of these trails showed a reduction in the surface roughness of micro-channels drawn over B-doped-ER micro-plates; the lowest roughness (~ 1.88 μm) was recorded for micro-plates fabricated at a laser power of 1.8 W and a high scanning speed of 20 mm/s with incorporating 15% BA. Also, a slight bulge height (≤ 6 µm) was obtained for all fabricated B-doped-ER micro-plates and the lowest value (0.022 µm) for BA-doped-ER fabricated at 1.8 W and 20 mm/s using 15% BA. In respect of the suitability of the fabricated B-doped ER-based microfluidic platform for bio-biomedical and analytical applications such as DNA amplification, it was demonstrated that these platforms have good autoclaving standability and PCR compatibility as well as no release for any components that would interfere with or inhibit the biological components employed in these analyses. This study validated the incorporation of boric acid into the ER matrix to enhance the thermal stability of the cured epoxy resin, which led to improved micro-the quality of the micro-channel with no negative impacts on the biological reactions. Therefore, the B-doped ER microfluidic devices developed in this study can be considered promising candidates for bio-analytical applications.Microfluidic devices based on novel boron-doped epoxy resin were successfully fabricated using casting and solvent evaporation followed by micromachining with mask-less, simple, and rapid CO2 laser ablation technique. Modification of epoxy resin compositions was achieved by incorporating HSupplementary Tables.


But the molecular mechanism linking AEA signaling to HPC proliferation and/or differentiation has not been explored. Here, we show that in vitro exposure of HPCs to AEA triggers both cell cycling and differentiation along with increased expression of Cnr1, Krt19, and Axin2. Mechanistically, we found that AEA promotes the nuclear localization of the transcription factor β-catenin, with subsequent induction of its downstream targets. Systemic analyses of cells after CRISPR-mediated knockout of the β-catenin-regulated transcriptome revealed that AEA modulates β-catenin-dependent cell cycling and differentiation, as well as interleukin pathways. Further, we found that AEA promotes OXPHOS in HPCs when amino acids and glucose are readily available as substrates, but AEA inhibits it when the cells rely primarily on fatty acid oxidation. Thus, the endocannabinoid system promotes hepatocyte renewal and maturation by stimulating the proliferation of Axin2+Cnr1+ HPCs via the β-catenin pathways while modulating the metabolic activity of their precursor cells.The proliferation and differentiation of hepatic progenitor cells (HPCs) drive the homeostatic renewal of the liver under diverse conditions. Liver regeneration is associated with an increase in Axin2 Suchem (ECS) –6. Furthem (ECS) , 8 and aem (ECS) –11.+ hepatic progenitor cells are the source of clones of hepatocytes expanding from the central vein towards the portal vein and are responsible for the natural homeostatic renewal of the liver [+Cnr1+ HPC cells in liver regeneration and the interplay of the ECS with the β-catenin pathways as a regulatory mechanism. We also investigated the role of the endogenous endocannabinoid, anandamide (AEA), in mitochondrial energy metabolism—in Axin2+Cnr1+ HPCs at the molecular level during liver regeneration.Oval cells, which are liver cells with a high nuclear:cytoplasmic ratio and an ovoid nucleus, are generally considered hepatic progenitor cells (HPCs) . They arhe liver . Axin2 ehe liver . Recentlhe liver , 20. The+ cells and the ECS and its role in liver regeneration, we used the in situ hybridization RNAscope technique to analyze the mRNA levels of Axin2 and Cnr1 in the remnant liver at 0 and 40 h following 2/3rd partial hepatectomy (PHx) in mice. We found a strikingly greater degree of Axin2 expression at 40 h post-PHx compared to baseline, which was accompanied by greater expression of Cnr1, and there was notable co-localization of Cnr1 and Axin2 staining in the same cells   Fig. , indicatTo understand the mechanistic role of AEA in cell proliferation of HPCs, we performed transcriptome analyses of mouse HPCs (BMOL) using a pool of six samples from such cells treated either with vehicle or AEA at 0.3 µM. GeneGo analyses of the transcriptome indicated that AEA markedly upregulated the expression of cell cycle proteins involved in G1/S transition, as well as Ras and Rho proteins in HPCs. Transcripts differentially expressed by >20% are illustrated in a heatmap Fig. .Ccnd1 (encoding cyclin D1) and its regulator Ctnnb1 (encoding β-catenin)  was verified by real-time PCR . The most robustly induced pathway was the TGFβ receptor signaling pathway, of which 56 genes were altered in response to AEA treatment. Similarly, large differences in transcript abundance were observed in a gene network laden with transcription factors involved in the segregation of the hepatocytic lineage. The AEA-induced enrichment of genes within these two pathways was statistically significant. The top inducible targets were in) Fig. . InductiPCR Fig. . AEA-indata Fig. .Ccnd1 and Axin2 were induced in mouse liver by PHx, and both are known to be regulated by β-catenin [Axin2, Cnr1, and an additional progenitor cell marker Krt19 (encoding CK19) in HPCs, we performed RNAscope analyses in both mice and rat HPCs. HPC proliferation induced by 0.3 µM AEA was associated with increased expression of Axin2, Cnr1, and Krt19, and there was a partial co-expression of these three transcripts in the same cells , including a clonal population, which was further confirmed by DNA sequencing , high g-score (33.12) and high Z-score  with a low false discovery rate (FDR = 7.905e−4)  with a low false discovery rate (FDR = 6.010e−7)  and has a low false discovery rate (FDR = 5.519e−9)  were induced by AEA, and such inductions were absent in the β-catenin KO cell line. HIF1a and Bnip3, which encode for factors in the hypoxia pathway, were also induced by AEA in wild-type but not in β-catenin KO cells  on the hepatocyte differentiation markers HNF4 and albumin Fig. . AEA sig+Cnr1+ HPC cell line, we quantified parameters of mitochondrial respiration in BMOL cells by Seahorse instrument analysis. In an assay medium supplemented with 1 mM pyruvate, 2 mM glutamine, and 10 mM glucose (“Full Substrate”), the addition of 0.3 μM AEA significantly increased the oxygen consumption rate (OCR) under both basal and maximally stressed conditions and increased ATP production , which were similarly modulated by PHX [TgfβR1 and Cdc42, are also induced following PHX [Ctnnb1 (encoding β-catenin) and Ccnd1 (encoding Cyclin D1), proteins that are known to have crucial roles in hepatocyte lineage differentiation.Transcriptome analyses had been previously used to uncover novel metabolic pathways in liver diseases , 37. In d by PHX , 38–40. wing PHX . Notably+ cell proliferation also correlated with enhanced expression of CB1R and cytokeratin 19 (CK19) in both mouse and rat HPCs. CK19 is commonly used as an HPC marker, and its increased expression has also been reported in patients with hepatocellular carcinoma (HCC) [Cnr1 expression, this is in agreement with earlier findings of the autoinduction of Cnr1 expression by CB1R activation [Endocannabinoid-mediated Axin2ma (HCC) , 43. As tivation .1R activation was also reported to have a pathogenic role in these conditions [1R and β-catenin.To understand the mechanism by which endocannabinoids induce Axin2 expression, we analyzed the expression of its transcriptional regulator β-catenin. In mouse HPCs treated with AEA, distinct mesh-like staining of β-catenin appeared to accumulate around the nuclear membrane. Staining was also observed in many cell nuclei and the plasma membrane when viewed at higher magnification. Furthermore, numerous β-catenin target genes were induced, suggesting that nuclear localization of β-catenin resulted in the activation of downstream targets. AEA-induced nuclear localization of β-catenin and induction of its target genes were also evident in rat HPCs. These data support the hypothesis that endocannabinoids activate β-catenin and its downstream targets in HPCs. β-catenin plays a pivotal role in the development of alcohol-associated liver steatosis, bile duct carcinoma and HCC –47. CB1Rnditions , 11, whiTo further interrogate the link between β-catenin and endocannabinoid-induced HPC proliferation and differentiation, we generated β-catenin-deficient HPCs by CRISPR-Cas9 and analyzed the differential effects of AEA on gene expression in the KO cells and their wild-type controls using whole transcriptome analyses. Heatmap representation of those gene networks demonstrated a critical role for β-catenin in AEA-induced network processes including essential proteins, such as transcription factors, enzymes, receptors, kinases, proteases and phosphatases. Specifically, we screened for genes induced by AEA by more than 50% in wild-type but not in β-catenin KO cells. When subjected to GeneGo analyses, the most strongly induced genes fulfilling this criterion were components of cell differentiation and cell cycle-proliferation pathways. The expression pattern of these genes was further validated by real-time PCR, which supported the key role of β-catenin pathways in AEA-induced proliferation and differentiation of HPCs.Most cell cycle and cell proliferative genes were constitutively upregulated in β-catenin KO cells, indicating loss of regulation. β-catenin interacts with many cell cycle proteins and transcription factors and its absence may trigger compensatory mechanisms unrelated to its regulatory pathways. Thyroid hormone receptor β agonizts also induce hepatocyte proliferation in mice during liver regeneration and the same β-catenin pathway is involved .Xenopus embryos [1R signaling plays a critical role in liver development in Danio rerio (zebrafish) embryos [Our transcriptome data indicated significant activation of both β-catenin signaling and TGF-β receptor signaling pathways by AEA. This suggests that during liver regeneration, endocannabinoids not only promote cell cycle progression but also stimulate the maturation of HPCs. Previously, β-catenin was implicated in lineage reprogramming of hepatic cells in the endoderm of  embryos . CB1R si embryos . Transcr embryos . Another embryos , during 1R activation promotes maturation of cells in the hepatocyte lineage. AEA likely has a similar role in the regenerating liver, as suggested by its marked and sustained increase in the remnant liver following PHx [1R activation and β-catenin expression, we may infer that β-catenin is responsible for the endocannabinoid-mediated initiation of hepatocyte maturation. This, of course, does not negate the possible role of numerous other paracrine factors in the hepatocyte maturation process.To further dissect the molecular machinery involved in the initiation of differentiation, we incubated wild-type and β-catenin KO mouse HPCs with AEA for five days and estimated the cellular levels of the hepatocyte markers HNF4 and albumin , 54, by wing PHx , 8. Beca+ HPCs are preferentially localized in the perivenous region where the hypoxic milieu promotes their maintenance in the quiescent state, by analogy to hematopoietic stem cells localized in hypoxic niches of the bone marrow [HIF1α and Bnip3 expression in a β-catenin-dependent manner. Wnt-β-catenin signaling in the liver was shown to promote cell proliferation by increasing glutamine metabolism [There is a physiological gradient in the liver where the oxygen tension of 60–65 mmHg in the periportal region declines to 30–35 mmHg in the perivenous zone 3 regions . Axin2+ e marrow . Under te marrow . Hypoxiatabolism . HIF1α itabolism . Togethe1R activation to inhibit fatty acid oxidation in a variety of tissues, including liver [1R by AEA promotes the terminal differentiation of hepatocytes, which would require a brake on the energetic support of cell proliferation. Inhibition of OXPHOS may also be a mechanism to preserve the self-renewing potential of HPCs and prevent their senescence and depletion that can result from uncontrolled proliferation.The most striking effect of AEA was modulation of mitochondrial energy metabolism. Mitochondrial energy metabolism plays a critical role in immune cell differentiation and cell cycle , 62. In ng liver , 63, brong liver , kidney ng liver , sperm cng liver , and ghrng liver . As disc+Cnr1+ HPCs have a unique endogenous cannabinoid-modulated role in hepatic cell proliferation, maturation and metabolic remodeling during liver regeneration. These findings could potentially be leveraged to improve liver regeneration and thus treat acute liver failure or organ dysfunction in chronic liver disease.A limitation of this study is that primary HPCs were not studied due to technical challenges of indistinguishable heterogeneous population of HPCs and hepatocytes in the PHx model. However, the insight that Axin2Mouse BMOL hepatocyte progenitor cells and permission for their genetic manipulation were obtained from Dr. George Yeoh . Cells were cultured in Williams’ E medium containing 5% FCS, antibiotics, glutamine, 20 ng/mL epidermal growth factor (BD Biosciences) and 30 ng/mL human insulin (Sigma-Aldrich) .The rat LE2 non-tumorigenic hepatocyte progenitor cell line was generated by Dr. N. Fausto’s lab  and was All other methods are provided with details as supplemental materials.Supplemental MethodSupplemental Figure legendsFigure S1Figure S2Figure S3Figure S4Figure S5RNASEQ dataOriginal Data File


Here, to address this challenge, two highly robust Hoffmann-type metal-organic frameworks are rationally applied as the NH3 sensing materials which possess ultra-high static adsorption capacity for NH3, only lower than the current benchmark material. The adsorption mechanism is in-depth unveiled by dynamic adsorption and simulation studies. The assembled interdigital electrode device exhibits low detection limit (25 ppb) and short response time (5 s) at room temperature, which set a record among all electrical signal sensors. Moreover, the sensor exhibits excellent selectivity towards NH3 in the presence of 13 other potential interfering gases. Prominently, the sensor can stably output signals for more than two months at room temperature and can be recovered by simply purging nitrogen at room temperature without heating. This study opens up a way for reasonably designing gas sensing materials for toxic gases.The development of fast-response sensors for detecting NH Developing fast-responsive NH3 sensors at room temperature is challenging. Here the authors developed robust Hoffmann-type MOF based NH3 sensors with a low detection limit (25 ppb) and quick response (5 s). The sensors exhibit high NH3 selectivity, stability, and easy recovery. Meanwhile, NH3 is also a colorless, irritating and corrosive gas with high toxicity4. Long-term exposure to NH3 with a concentration greater than 50 ppm will lead to temporary blindness, pulmonary edema, and even death. Occupational Safety and Health Administration has set a limit of 300 ppm for industrial environments5. Therefore, the detection and sensing of NH3 are of great significance for environmental protection and human health. Currently, the use of metal oxides as the affinity layer is the mainstream in commercial NH3 sensors. However, drawbacks still exist for current detection devices, e.g., low selectivity and high operating temperatures. Therefore, the rational design of advanced materials for NH3 sensing at ambient conditions  with high selectivity is urgently needed.Ammonia  can adjust the host-guest interaction at the molecular level, which is the potential to offer high selectivity to targeted guest molecules. More importantly, the physical adsorption/desorption with good recyclability will endow MOF-based gas sensors with long-term reliability. Therefore, MOF-based gas sensors have been gaining increasing attention in recent years13. Although significant progress has been made in gas sensing using MOFs, the development of MOFs for NH3 sensing is still in its infancy. Firstly, most MOFs exhibit structural degradation after adsorbing NH3 and low binding affinity to NH3, hindering the application of MOFs as NH3 sensors. Secondly, the mechanism of NH3 sensing is not well understood, mainly due to the lack of appropriate techniques such as adsorption kinetics and molecular simulation. Thirdly, currently reported MOF materials often require additional material doping for sensing , which in turn requires complex fabrication procedures and even high-temperature sensing conditions, complicating the sensor device. Using pure MOF materials for NH3 sensing applications is still very rare and all currently reported examples suffer from expensive ligands which are not readily available , leading to increased operating costs. Hence, it is of great significance to reasonably design cost-efficient and high-performance MOF materials for NH3 sensing at room temperature.Metal-organic frameworks (MOFs) possess tailored structures, high porosity, and customizable functionalities are considered to be a promising choice to serve as the affinity layer of gas sensors3 environment. (ii) In order to achieve strong NH3 binding capacity, MOFs with open metal sites (OMS) and micropores are preferred; (iii) Low-cost and large-scale preparation of MOFs is a key requirement for industrial applications such as toxic gases and air filters. Thus, we delicately choose two highly robust Hofmann-type MOFs, Ni(pyz)[Ni(CN)4] and Co(pyz)[Ni(CN)4] , as the sensing materials for detecting NH3. Although these two materials have been previously reported for application in gas separation21, they have not yet been investigated for sensing application. Their high-performance interdigitated electrode (IDE) sensors have been successfully fabricated and used for NH3 sensing  High structural robustness is required to prohibit the structure collapse in the NH3)2·6H2O, pyrazine and K2[Ni(CN)4] in a green synthesis fashion . The crystal structures of MNi-Pyz were confirmed by powder X-ray diffraction (PXRD) pattern, which was consistent with that of the simulated structure, indicating the high phase purity  square channels along the a-axis direction. The M2+ ions with unsaturated metal sites are uniformly arranged on the walls of 1D channels  were prepared through the reaction M surface area of NiNi-Pyz and CoNi-Pyz were 488 and 585 m2·g−1 with the pore size distribution around 7.2 Å and 6.8 Å, respectively , or acid solution (pH = 1) treatment for one day  and famous MOFs (Cu(cyhdc)23, 17.5 mmol·g−1 and Cu2Cl2BBTA24, 19.7 mmol·g−1), and only slightly lower than the benchmark MOF (LiCl@MIL-53-(OH)225, 33.9 mmol·g−1). Nevertheless, taking into account the green, cheap raw materials and low energy consumption in the preparation process, MNi-Pyz can easily surpass the current benchmark MOF in terms of cost. The excellent NH3 capture ability of MNi-Pyz MOFs could be due to their special pore microenvironment with enriched open metal sites and strong regional restriction effect for NH3. In the real world, the competitive adsorptions of H2O and NH3 often occur due to the similar molecular properties of H2O and NH3. Adsorbents with high NH3 uptake but relatively low uptake of water are desirable. Therefore, we tested the water vapor adsorption isotherms for MNi-Pyz. When the relative humidity (RH) rises to 60%, the water vapor adsorption capacities of NiNi-Pyz and CoNi-Pyz are 1.16 and 1.88 mmol·g−1, respectively. When the humidity rises to 90% RH, MNi-Pyz still maintains a low water vapor adsorption capacity of 1.7 mmol·g−1 −1. These results indicated that both NiNi-Pyz and CoNi-Pyz exhibited fast dynamic adsorption for NH3. Notably, NiNi-Pyz has a higher average adsorption rate than CoNi-Pyz possibly because NiNi-Pyz had a higher density of open metal sites (NiNi-Pyz: 9.29 mmol·cm−3 and CoNi-Pyz: 8.97 mmol·cm−3). The fast adsorption performance in kinetics lays a solid foundation for sensing applications.The rapid adsorption of NHPyz Fig. . The exp3 capture behavior of MNi-Pyz, we conducted Monte Carlo simulations (GCMC) performed to investigate the interactions between materials and NH3. The total adsorption field shows that NH3 is stably bound inside the cavity of MNi-Pyz, due to the gas molecules being subject to the barrier of surrounding ligands  sites in the NiNi-Pyz square channel, with a distance of 2.709 Å. A sandwich-like binding environment is constructed, which is attributed to the strong interaction between the N atom of NH3 and Ni2+. For the adsorption site II 4]2− to generate a strong electrostatic attraction, increasing the van der Waals interaction forces between NH3 and ligands. In addition, the N atom of NH3 can achieve conjugation with the large π bond on the pyrazine ring to achieve dual and strong interactions. For site III 4]2− because of hyperconjugation. More importantly, NH3 molecule itself tends to form dimers29. When further adsorption occurs, NH3 are close to each other due to the effect of orientation force. Finally, hydrogen atoms are inserted into the electronic cloud of nitrogen atoms, and the two NH3 molecules are combined by overlapping orbits to form adsorption site III. For CoNi-Pyz materials, there are four NH3 molecular interaction sites  sites in the square channel, showing a lateral binding mode, thus forming a sandwich-like binding environment. For site II, the electrostatic attraction between NH3 molecule and the N atom of [Ni(CN)4]2− and the conjugation with a large π bond on the pyrazine ring realize strong interaction. For site III, when further adsorption occurs, the N atom has a partial negative charge, while the H atom has a partial positive charge. Due to the effect of orientation force, a dimer is formed to act on site III. Besides, CoNi-Pyz has an additional adsorption site IV with a weak force. In this site, NH3 molecules mainly exist in the middle of the pore, which may be due to the larger surface area of CoNi-Pyz, so it can accommodate more NH3 molecules. Furthermore, the interaction energy between NH3 and MNi-Pyz was calculated using the Density functional theory (DFT) method (Supplementary Table 3 pressure). The high total adsorption energy also implies that CoNi-Pyz has a higher NH3 capture capacity than NiNi-Pyz. The independent action and mutual cooperation of all binding sites reveal the key points and mechanism of strong NH3 capture and detection performance of MNi-Pyz. Simultaneously, we conducted simulations to analyze the adsorption sites and energies of MNi-Pyz materials towards three common air gases , as well as three typical volatile organic compounds . The findings demonstrated that MNi-Pyz materials exhibit higher adsorption energy for NH3, and relatively lower binding energy for other gas molecules, which further confirms the specific recognition capability towards NH3 of MNi-Pyz materials  after one day 18, Cu-BHT film32 and NiPc-Ni33. Notably, the sensing response time of MNi-Pyz surpasses all reported MOF materials. On a wider scale, compared to other excellent NH3-sensing electrical signal materials reported so far -Response(N2)/Response(N2)) towards interference gases, indicating their excellent selectivity. Furthermore, to verify the practicality of the sensor, we explored the sensor signal in a real air atmosphere . From Supplementary Figs. Additionally, one of the most important evaluation parameters of the sensor includes stability and reproducibility. In this regard, we conducted a cyclic stability test on MNi-Pyz of 1 ~ 1000 ppm NH8 K Fig. . ThroughNH3 Fig. . The tes3 sensing behavior of the MNi-Pyz sensor under varying relative humidity (RH) conditions of 12, 35, 75, and 90% [Ni(CN)4], were rationally applied as the sensing materials for detecting NH3. Due to the high density, ultra microporous structure, and strong regional limitations of OMS, the static adsorption capacity of MNi-Pyz for NH3 reached 29.1 mmol·g−1 at 298 K and 1 bar, which was more than three times the capacity of industrial standard zeolites (13X Zeolite) and only lower than the current benchmark MOF (LiCl@MIL-53-(OH)2). The adsorption kinetics showed that the materials reached adsorption saturation at low concentration within 20 s, and the maximum adsorption rate was as high as 1.67 mmol·(g·s)−1, demonstrating the rapid NH3 capture performance. Additionally, GCMC simulation calculations indicated there were three priority adsorption sites for NH3 with unsaturated metal sites as the primary adsorption sites. Furthermore, the assembled IDE device was used as an NH3 sensor, capable of detecting NH3 in a low concentration range of 1–1000 ppm. These sensors exhibited a low detection limit of 25 ppb and a fast response time of 5 s at room temperature, exhibiting the fastest response speed among all reported electrical signal sensing materials at room temperature. Excellently, the sensor can be recovered by simply purging nitrogen at room temperature, and the response signal can stably output for at least two months at room temperature. In addition, MNi-Pyz-sensors exhibited excellent selectivity towards NH3 in the presence of 13 other potential interfering gases. Prominently, this work provides important guidance for the design and manufacture of high-performance sensors operating at room temperature.In summary, two Hoffmann-type MOFs, Ni(pyz) were purchased from Aladdin (98% purity), pyrazine was purchased from Macklin (98% purity).Unless otherwise stated, all materials were commercially available and used without further purification. Ni(NO49. M(NO3)2·6H2O  was dissolved in a mixture of methanol (15 mL) and deionized water (15 mL). Pyrazine  was dissolved in a mixture of methanol (15 mL) and deionized water (15 mL). When they were completely dissolved, the two solutions were combined and stirred. Subsequently, K2[Ni(CN)4]  was dissolved in deionized water (5 mL), and dropped into the above mixture with constant stirring. After 8 min, the reactant was centrifuged to obtain the corresponding purple and pink powder samples for NiNi-Pyz and CoNi-Pyz, respectively. The materials were washed twice with deionized water and methanol, and then dried in a vacuum drying oven until use.The synthesis method of MNi-Pyz is fine-tuned on the basis of literature reportso) min−1, scanning step 0.02 (o) and scanning range 5 (o)–40 (o). For Temperature-dependent PXRD, the measured parameter included a scan speed of 5 ° min−1, a step size of 0.02 (°) and a scan range of 2θ from 5 (°) to 40 (°).In this experiment, Rigaku Altima IV powder diffractometer from Japanese Neo Confucianism was used for relevant tests. The diffractometer parameters were set as follows: 40 kV, 40 mA, CuK α 1,2 λ = 1.5418 Å. The measurement parameters included scanning speed 5  in air atmosphere using crucible.TGA was conducted on Netzsch STA449F3 thermal analyzer from room temperature to 800 °C , pH = 13 (NaOH), and boiled water for one day, respectively. Further, prepare saturated KCl (RH = 85%) solution, put the saturated solution and the vial containing MNi-Pyz into a large beaker, seal the beaker with a preservative film and place it at room temperature. The treated MNi-Pyz samples were washed with methanol several times and dried at room temperature before PXRD measurements.3 stability, calculate the volume of the seal pipe, put MNi-Pyz into the seal pipe, extract and empty the gas inside. Then, according to the definition of parts per million (ppm) a certain volume proportion of NH3 is injected into the sealed pipe, sealed tightly, and placed at room temperature to study their gas stability.For NHIn this experiment, we used the BSD-PMC1 adsorption instrument of Beishide Instrument Company. The specific method is as follows: using MNi-Pyz (150–250 mg) to test the single component gas adsorption curve, the test temperatures are 273 K and 298 K.3 were measured on the BSD-PMC adsorption instrument. About 50 mg of NiNi-Pyz and CoNi-Pyz were first loaded to the sample chamber and activated at 150 °C under high vacuum for 8 h. After cooling to a specific temperature, 1 bar of NH3 is introduced into the chamber. With the progress of material adsorption, the NH3 pressure change every second is recorded, so as to judge the mass of the sample loaded with gas molecules. As the completion of NH3 consumption in the chamber, after the instrument is balanced for a period of time, a certain amount of gas will be automatically introduced for continuous test recording.The time-dependent adsorption curves of MNi-Pyz on NH3, Grand Canonical Monte Carlo (GCMC) simulation was carried out on Materials Studio 2019 version. Considering the rigidity of the frame, the forcite module was used to optimize the geometry of MNi-Pyz and NH3. Under the condition of ultra-fine mass, the universal force field (UFF) is used to model it to reach the minimum energy. The partial charge of atoms in the frame is determined by QEq method, detailed structural information can be found in Supplementary Data 5, and the production step is 1 × 106. The calculation formula of the binding energy between the skeleton and gas molecule is: ΔE = E(MOF) + E(gas)-E(MOF + gas).In order to better understand the adsorption behavior of MNi-Pyz on NHUse self-built equipment to test the sensing signal. The gas sensor test by using HIOKI LCR-3536 full-automatic measurement system, and the clamp is L2000-four terminal Kelvin clamp. To reduce the disturbance of noise, insert the noise filter into the power line during testing. Before each test, perform open circuit compensation and short circuit compensation on the instrument, ranging from 4 Hz to 8 MHz, to reduce testing errors and select LCR for measurement mode. The measurement frequency is set to 8 kHz, the test signal level V is set to 5 V, the limit value is adjusted to OFF; select internal trigger mode, set the range to AuTo (1 kΩ~1 MΩ), Low Z selects OFF mode, measurement speed is MED, and the average number of times is three; trigger delay of 0.000 s; DC bias setting OFF, DC adjustment function setting On, JUDGE SYN setting ON.−1. After, about 200 µL suspension droplets were applied to the electrode and dried naturally in air to form a film. Then the coating sensor is placed in the self-made testing room, and the material is connected to the LCR instrument with a clamp to detect the change of electrical signal, the sensor unit is installed on the sensor equipment through two probes. Before the test, the sample is first activated under vacuum at 80 °C for 2 h (this activation process only needs to be done once before the first use of the sensor), then the test chamber is purged with pure nitrogen to remove the substances left in the chamber until the baseline is balanced. The subsequent material activation steps can be achieved only by blowing with pure nitrogen gas. When the chamber is filled with nitrogen atmosphere, the chamber exhaust valve is closed to keep it in a closed environment, and then a certain volume of NH3 is injected through a micro syringe to test the NH3 sensing performance. To control the tested gas/steam concentration, we calculated the required gas volume in detail according to the definition of the fixed volume of the chamber (220 cm³), ppm (parts per million concentration) and the Antoine equation53. For Antoine formula, the constants A, B and C for the measured gases are given in Supplementary Table P is the vapor pressure of the substance in mmHg; t is the temperature in °C. Equation  value — representing the noise-based deviation in ∆R/R0 — was calculated using the baseline trace before exposure to analyte. We took 600–1000 consecutive points (N) and fit the data to a polynomial. We then calculated sum of squared residuals (SSR) from Eq. (0) after a specific exposure time and isolated the range of values wherein this relationship was linear. Linear regression provided an equation of best-fit (slope = m). With these values, we extrapolated the theoretical LOD from Eq.  were calculated using reported protocolsSupplementary InformationPeer Review FileDescription of Additional Supplementary FilesSupplementary Data 1


Metasurfaces attracted extensive interests due to their outstanding ability to manipulate the wavefront at a subwavelength scale. In this study, we demonstrated quasi-freeform metasurfaces in which the radius, location, and height of the nanocylinder building blocks were set as optimized structure parameters, providing more degrees of freedom compared with traditional gradient metasurfaces. Given a desired wavefront shaping objective, these structure parameters can be collectively optimized utilizing a hybrid optimized algorithm. To demonstrate the versatility and feasibility of our method, we firstly proposed metasurfaces with deflecting efficiencies ranging from 86.2% to 94.8%, where the deflecting angles can vary in the range of 29°–75.6°. With further study, we applied our concept to realize a variety of high-efficiency, wide-angle, equal-power beam splitters. The total splitting efficiencies of all the proposed beam splitters exceeded 89.4%, where a highest efficiency of 97.6%, a maximum splitting angle of 75.6°, and a splitting uniformity of 0.33% were obtained. Considering that various deflecting angles, and various splitting channels with different splitting angles, can be realized by setting the optical response of metasurfaces as the optimization target, we believe that our method will provide an alternative approach for metasurfaces to realize desired wavefront shaping. Beam deflectors and splitters play a critical role in various optical and photonic systems, such as optical holography, spectroscopy, interferometers, sensing, and optical communications ,2,3,4. TFor a large portion of metasurfaces, the geometrical parameters of the building blocks are determined by forward design method ,17,18. Aentation ,20. Howeentation . A largeentation . Alternative approaches for realizing high efficiency deflecting and splitting with wide angle are based on inverse design concept. The inverse optimization methods brought promise to metasurfaces beyond the capabilities of traditional methods, such as broadband response, unconventional electronic logic gate, multiplexed response, large numerical apertures, and high efficiencies ,24. In tIn this paper, we proposed quasi-freeform metasurfaces to realize wide-angle, high efficiency beam deflecting and splitting. The supercells inside the metasurfaces were defined as an ensemble of simple nanocylinders that were collectively optimized by a hybrid optimization algorithm. The radius and location of each nanocylinder, and the height of the supercells, were optimized structure parameters. To illustrate the feasibility and versatility of the proposed method, we begin with demonstrating six metasurfaces for deflecting incident light to +1 channel with deflecting angles ranging from 29° to 75.6°. The deflecting efficiencies were higher than 86.2% and the highest deflecting efficiency reached 94.8% at 56.4° after optimization. With further study, we applied our concept to realize a variety of wide-angle, high efficiency, equal-power beam splitters. In the design of the beam splitters, we started by optimizing metasurfaces with three port splitting output with the maximum splitting angles ranging from 29° to 75.6° and splitting efficiencies ranging from 89.4% to 95.7%. Additionally, metasurface with five port splitting output was then proposed, where the overall efficiency and splitting uniformity were 93.6% and 5.5%, respectively. The beam splitters mentioned above adopted the asymmetrical structure to generate more degrees of freedom. Apart from the asymmetrical structure, we also proposed metasurfaces with symmetrical structure to realize beam splitting. By adopting symmetrical structure with a smaller number of structure parameters, we further addressed metasurfaces for generating five and seven port splitting output. In the two optimized metasurfaces with a maximum splitting angle reaching 75.6°, the total splitting efficiencies reached 97.6% and 95%, and the splitting uniformity were 2.7% and 4.7%, respectively. Those cases studies proved that various deflecting angles, and various splitting channels with different splitting angles, can be realized by setting the optical response of the quasi-freeform metasurfaces as the optimization target. In general, the inversely designed quasi-freeform metasurfaces provided useful insights into the design of metasurfaces for realizing desired wavefront shaping, especially for realizing wide-angle deflecting and splitting. 2 substrate. The refractive index of Si and SiO2 were x direction. n channel, respectively. n channel can be calculated by:The quasi-freeform metasurfaces were composed of periodic supercells, as illustrated in g theory :(1)PXsiny direction was set to 640 nm to allow only zeroth-order diffraction in y direction. Based on the above equations, different deflecting or splitting angles designs can be obtained by varying the period length Supercells with asymmetrical and symmetrical structure were proposed in this paper. The schematics of the supercells are shown in x and y directions. The perfectly matched layers were used along the incident z direction. The efficiency of each channel was obtained from the grating transmission analysis group which was set on the x-y plane. The optimization-based inverse design methodology consisted of an electromagnetic solver and an objective optimizer based on algorithm, as shown in x direction, the locations of the nanocylinders were set to meet The backward optimizer can be realized by any optimization algorithms, such as genetic algorithm (GA) ,36, topoFOM) functions. In the design of beam deflectors, the goal was to deflect the incident light to a selected diffraction channel with high efficiency. To realize high beam deflecting efficiency, we defined the figure of merit as following equation: n. As for the design of beam splitters, the ultimate target was to equally split the incident light into selected diffraction channels with high efficiency. Therefore, to optimize the overall splitting efficiency and the splitting uniformity simultaneously, we defined the figure of merit as:In this paper, the structure parameters of the metasurfaces were optimized for realizing two kinds of optical responses. Thus, two equations were required to define the figure of merit (Firstly, we addressed a set of metasurfaces that can deflect the normally incident light to +1 channel with deflecting angles ranging from 28.97° to 75.64°. Six supercells, named D1, D2, D3, D4, D5, D6, were designed by the inverse design methodology in To demonstrate the advantages of the proposed beam deflectors based on our method, a comparison between some previously reported studies and the proposed beam deflectors are listed in Apart from the optimization of metasurfaces for beam deflecting, our optimization strategy can also readily generalize to the design of high efficiency, equal power beam splitting. In order to further verify the feasibility and versatility of the proposed quasi-freeform metasurfaces, we demonstrated several sets of metasurfaces for three, five, and seven port splitting output. In the design of beam splitting, two types of supercells including asymmetrical and symmetrical structure were utilized. Both structures obtained high splitting performance after optimization. To reveal that different wavefront shaping tasks can be realized by modulating the figure of merit function, six supercells mentioned in To further indicate the feasibility of our method, we addressed metasurface for generating wide-angle five-port splitting output. Here, the undesired In addition to the asymmetrical structure, we, furthermore, proposed quasi-freeform metasurfaces that adopted the symmetry structure, which can also realize high efficiency and equal power beam splitting while using less optimized parameters. As shown in The first symmetrical supercell, named supercell S8, contained five nanocylinders. The period length The second symmetrical supercell had a supercell period To reveal the diffraction performances of the inversely designed quasi-freeform metasurfaces, a comparison between the previously reported metasurface-based beam splitters and the proposed beam splitters is presented in Some previous reported metasurfaces can realize polarization-insensitive beam splitting. The beam splitters in this paper could not always maintain high splitting performance under y-polarization incident. Here, we explored the performance of the proposed beam deflectors and splitters in waveband. We calculated the deflecting and splitting performance of the optimized supercells with a wavelength scanning from 1500 nm to 1600 nm, as illustrated in The fabrication error was unavoidable in practice fabrication. The optimized supercell D1 and D2 were selected as examples for evaluating the effects of radius and height of the nanocylinders on the deflecting efficiency. The results, as depicted in In summary, we presented wide-angle, high efficiency beam deflectors and splitters based on quasi-freeform metasurfaces. In the quasi-freeform metasurfaces, the radius, location, and height of the nanocylinder building block in a supercell were set as the optimized structure parameters, which will provide more design degrees of freedom. The quasi-freeform metasurfaces proposed in this paper can combine the features of traditional and freeform metasurfaces. By setting the supercell towards a pre-set angle as the optimization target, various deflecting and splitting angles gratings were inversely designed by a hybrid optimization algorithm. In the design of beam deflectors, the deflection efficiencies ranging from 86.2% to 94.8% with the deflection angles varying in the range of 29°–75.6° were demonstrated. With further study, we demonstrated two kinds of metasurfaces, including asymmetrical and symmetrical metasurfaces, for wide-angle, high efficiency, equal-power beam splitting. In the design of beam splitters based on asymmetrical structure, the splitting efficiencies ranging from 89.4% to 95.7% with the splitting angles varying in the range of 29°–75.6° were obtained. Meanwhile, the splitting uniformities were lower than 5.5%. In the design of beam splitters based on symmetrical structure, a total splitting efficiency reaching 97.6% and 95%, with a splitting uniformity of 2.7% and 4.7%, were achieved for five-port and seven-port splitting output, respectively, where the maximum splitting angles of 75.6° were achieved in both designs. Additionally, broadband analysis indicated that the proposed metasurfaces have a certain broadband characteristic. Compared to traditional metasurfaces, the quasi-freeform metasurfaces provide more degrees of freedom, thus resulting in higher performance. Compared to fully freeform metasurfaces, the structures can avoid immense parameter optimization space while obtaining performances comparable to freeform metasurfaces. Overall, we believe that this work will provide an alternative approach for metasurface to realize desired wavefront shaping.