A high sensitivity chemiluminescence-based CMOS image biosensor for the detection of human interleukin 5 (IL-5)
In this study, a CMOS image sensor that converts light intensity to digital image data was used to detect human interleukin 5 (IL-5). Although the application of CMOS image sensors to biosensors is well known, a more sensitive method is needed to detect molecules with very low concentrations such as cytokines. For this reason, we have used a chemiluminescence reaction to increase the sensitivity of sandwich immunoassay in CMOS image sensor. Another approach used to obtain a high sensitivity response was the pixel counting analysis. By using pixel counting analysis, much more detailed luminescence signals can be obtained. The detection sensitivity of IL-5 we obtained in our experimental measurements was evaluated up to 0.1 pg/mL.
CMOS Active Column Sensor for Label-Free Biodetection in Microarrays based on Surface Plasmon Resonance (SPR)
This dissertation presents the design and implementation of a CMOS imager for use in integrated biosensors based on Surface Plasmon Resonance. First, the optimal conditions for plasmon resonance in a CMOS/Post-CMOS compatible interface are obtained by COMSOL modelling. Second, a 32×32-pixel CMOS-Active Column Sensor (CMOS-ACS) is implemented in a 0.35 μm CMOS technology. In a gold-water interface with prism excitation and wavelength of 633 nm, it is found that for prisms with refractive indexes of 1.55 and 1.46, the optimal plasmon coupling occurs at incidence angles of 68.45◦ and 79.05◦ and gold layer thicknesses of 50 nm and 45 nm, respectively. Under these conditions, approximately 99.19% and 99.99% of the incident light energy is transferred to the surface plasmon. It is also obtained that a change of 10−4 RIU in the refractive index of the dielectric medium, produces a change of 0.01◦ in the plasmon resonance angle, which under a light intensity modulation scheme represents a change of 0.08% in the reflected light's energy reaching the photodetector. Concerning the CMOS imager, a n-well/p-substrate photodiode is selected as the photosensing element, due to its low junction capacitance, which results in high efficiency and high conversion gain. Computer simulations with Cadence and Silvaco produced a junction capacitance of 31 fF and a maximum quantum efficiency of 82%. The imager's pixel is based on a three-transistor (3T) configuration and shows a fill factor of 61%. The readout circuitry employs an Active Column Sensor (ACS) technique to reduce the Fixed Pattern Noise (FPN) associated with traditional Active Pixel Sensors (APS). Additionally, Non-Correlated Double Sampling (NCDS) and Delta Double Sampling (DDS) are used as noise reduction techniques. An experimental optical setup is used to characterize the performance of the imager, obtaining a conversion gain of 7.3 μV/e− , a photodiode junction capacitance of 21.9 fF, a read noise of 324.5 μV, equivalent to ∼45e− , and a dynamic range of 62.2 dB. The benefits of ACS and NCDS-DDS are observed in the low pixel and column FPN of 0.09% and 0.06% respectively. The work presented in this thesis is a first step towards the goal of developinga fully integrated SPR-biosensing platform incorporating light source, SPR interface, microfluidic channel, optical elements and CMOS imager.
Preparation and performance evaluation of swine manure bio-oil modified rubber asphalt binder
Abstract In order to study the effect of the preparation process of swine manure bio-oil modified rubber asphalt binder on the rheological properties of the binder, the matrix asphalt and asphalt rubber were used as the control group, and swine manure bio-oil modified rubber asphalt binders were obtained by three preparation processes. Then the rheological properties of five binders were evaluated by rotational viscosity, DSR, MSCR and BBR tests. The results show that the addition of swine manure bio-oil to asphalt rubber is beneficial to the workability, but cause negative effect on its high temperature performance, fatigue performance and low temperature crack resistance. The preparation method of premixing bio-oil and rubber powder can reduce the degradation of high-temperature performance of asphalt rubber caused by addition of swine manure bio-oil to a certain extent. The fatigue properties of the three bio-binders are close, and the critical temperature is less than 25 °C. The process of premixing bio-oil and rubber powder will increase the creep stiffness and reduce the low-temperature performance. However, the low-temperature performance of the binder obtained by this process is still better than that of the matrix asphalt and can meet the requirements of use. Therefore, it is recommended to use the preparation process of premixing bio-oil and rubber powder to prepare swine manure bio-oil modified asphalt rubber.