Aflatoxin is a potent biological toxin produced by fungi Aspergillus flavus and A. parasiticus. Current quantification methods for aflatoxins are mostly established on immunoaffinity columns which are both costly and labor intensive. Inspired by smectites’ high aflatoxin adsorption capacity and affinity, a novel aflatoxin quantification sensor based on smectite-polyacrylamide (PAM) nanocomposite was fabricated. First, a smectite-PAM nanocomposite film was synthesized on flat silicon substrates which assembled smectite particles from the clay suspension. A layer-by-layer assembly process was developed to achieve uniform morphology and thickness of the nanocomposite films. During the aflatoxin quantification process, positive correlations between the fluorescence intensity from the aflatoxin B1 (AFB1) adsorbed smectite-PAM nanocomposite films and the AFB1 concentration in the test solutions were obtained. The smectite-PAM nanocomposite film has shown similar AFB1 adsorption capabilities as the smectite. Second, the smectite-PAM nanocomposite film was optimized in order to achieve the aflatoxin quantification at ppb level (below 20ppb) in corn extraction solutions. The smectite was modified by Ba2+, which had demonstrated to be able to improve its aflatoxin adsorption capacity. PAM aqueous solutions with the mass concentration ranging from 0.8% to 0.001% were tested. The results showed that the nanocomposite synthesized from 0.005% concentration of PAM solution generated the best properties. After the optimization, the smectite-PAM nanocomposite films achieved the detection of aflatoxin B1, B2, G1 and G2 (AFB2, AFG1 and AFG2) in 10 ppb corn extraction solution. Aflatoxin quantifications in AFB1 and AFB2 mixture solution, AFB1 and AFB2 mixture solution and AFB1 and AFG1 mixture solution were conducted, and the recoveries of last test ranged from 90.52% to 110.11% at low aflatoxin concentration (below 20 ppb). Third, in order to shorten the quantification duration and simplify the detection process, a novel aflatoxin detection array based on smectite-PAM nanocomposite and an improved fluorometric quantification method were developed. Through a microfluidic chip, the reaction time was reduced to 10~20min. Two concentration levels (20~80ppb/5~15ppb) of aflatoxin B1 spiked corn extraction solutions were tested. In the fluorometric quantification step, a common lab-use 365 nm ultraviolet lamp replaced the spectrofluorometer which simplified and accelerated the process.

Mechanical rubbing alignment is the most common used method in the liquid crystal display manufacturing process. However, it may cause dust and electrostatic problem. In this study, we investigate effects of low surface free energy Polydimethylsiloxane (PDMS) on orientation of liquid crystal molecules in a confined structure and fabricate alignment layer using PDMS. In the present study, we show that liquid crystal molecules are arranged in consistency without rubbing process and it may be a new homogeneously aligned mode in liquid crystal display. In this thesis, liquid crystal textures were observed using polarizing optical microscopy (POM). It was found that liquid crystal molecules were homogeneously aligned in PDMS holes. In addition, this thesis indicated that how liquid crystal alignment affected by PDMS layer thickness and surface treatment. We learned that using treatment of JALS-9800 film on the bottom substrate from liquid crystal texture can obtain the arrangement of expected liquid crystal molecules. The liquid crystal device can be produced using PDMS structure. The measurement of electro-optic characteristics showed that the circular shape in the confined structure had better transmittance and contrast ratio.

The backlight module is usually used to increase visual angle and brightness of liquid crystal display (LCD). Thus, the design and fabrication of optical films, including light guide plate, diffuser film, and brightness enhancement film (BEF), are critical factors to decide the optical efficiency in a backlight module. In order to improve the optical efficiency for power-saved display with competitiveness, this study presents a new fabrication process combining precision machining, lithography, and hot-embossing techniques to form a two-side-patterned optical film. One side of the optical film is micro triangular-pyramidal array (MTPA) and the other is micro spherical lens array(MSLA). First, the Taguchi method is applied to design the optimal microstructure configuration by the assistance of the optical software, FRED. Second, a tungsten (W) steel mold (as the mold to hot emboss MTPA) is manufactured by precision machining including optical projection grinding, lapping, and polishing processes. Meanwhile, a nickel-cobalt (Ni-Co) mold (as the mold to hot emboss MSLA) is fabricated by electroplating process. Then, polydimethylsiloxane (PDMS) is used to replicate the MTPA and MSLA patterns, on W and Ni-Co metal molds, respectively, and the replicated PDMS films are used as the molds to form a two-side-patterned optical film. In addition, the optical property such as luminance is measured by photo research 650 (PR 650) to evidence the optical function of the two-side-patterned optical film. From the experimental results, both brightness and uniformity can be improved by this film;thus, optical efficiency is successfully increased in this study.

The deformation between interface, adhesion mechanism and the transparency of multi-layer flexible electronics composite were discussed. First, ITO (Indium Tin Oxide), Al (Aluminum) and ZnO (Zinc Oxide) were sputtered on a PET (Poly Ethylene Terephthalate) substrate by PVD (Physical Vapor Deposition) sequentially, to form ZnO/ITO/PET and ZnO/Al/PET which is the essential multi-layer structure in the transducer of flexible electronics. ITO/PET structure was widely applied to the touch panel. PET substrate possesses a good optical penetrability, low thermal expansion coefficient and lower price. However, the heat-resisting and chemical stability are poor. In this study, we explore the feasibility of the PDMS (Polydimethylsiloxane) substrate. It not only possesses good optical penetrability, but also exhibits higher PH selectivity than PET. In the analysis, the periodic external force was pressed on the flexible composite films to realize the difference between before and after experiment. Then the composite films were examined by nanoindentation and nanoscratch system (Berkovich and Conical probe with the radius of curvature of 20nm and 10um), four-point probe and spectrometer to measure the mechanical, electrical and optical properties, respectively. To investigate the effect of external force on these composite films, the interaction of films was discussed through external force testing by nanoscratch test.

PDMS has not only the characteristics of good chemical and physical properties,flexible, low surface free energy, and good optically transparent, also has the advantages of low cost, low toxicity and environmental protection. In this study we use PDMS to fabricate liquid crystal device with different micro-confined structures. We had a discussion about liquid crystal in the micro-confined structure through optical textures and measured electro-optical characteristics on our device. Through the experiment we found the liquid crystal device with micro-confined structure had not only the characteristics of wide viewing angle and contrast ratio has been up to standard in normal display. And it also demonstrated the capability in flexible liquid crystal display.

This thesis presents the development of a micro-aspirator chip using vacuum expanded microchannels for mechanical characterization of single cells. Mechanical properties of cells can offer valuable insights into the pathogenic basis of diseases and can serve as a biomarker to identify cells depending on disease state, and thus have the potential for use in human disease diagnostic applications. Micropipette aspiration and atomic force microscopy (AFM) are the most commonly used techniques for measuring mechanical properties of single cells. Though powerful and versatile, both methods have two drawbacks. First, micromanipulation of glass micropipettes and AFM tips require expertise and extensive operator skills. Second, the serial manipulation process severely limits the throughput. Although recently reported microfluidic micropipette device showed the potential of microfluidic chip type micropipette aspiration, difficulty in cell trapping and unnatural cell deformation remain to be solved. In order to address these limitations, a high-throughput micro-aspirator chip, which can deliver, trap, and deform multiple cells simultaneously with single-cell resolution without skill-dependent micromanipulation was developed. The micro-aspirator chip is composed of 20 arrays of cell traps and aspiration channels. The principle of cell trapping is based on differences in flow resistance inside the microfluidic channels. Once the first cell trap is filled with a cell, the next cell coming in passes by the trap and is captured in the next trap. After all traps are filled with cells, negative pressure can then be applied to the integrated aspiration channels using hydrostatic pressure. The aspiration channels are positioned at the center of a trapped cell both in vertical and horizontal directions to obtain a good seal just like a traditional micropipette, a design made possible through a vacuum expanded raised microfluidic channel fabrication technique. Device operation was demonstrated using HeLa cells. The cell trapping efficiency was almost 100 percent. Using this device, Young's modulus of 1.3 ± 0.8 kPa (n = 54) was obtained for HeLa cells. Device to device variation was less than 15.2 percent (n = 3), showing good repeatability of the device. No dependence of the Young's modulus on the cell diameter was found.

This research proposes a novel polymer-based optical waveguide made with Polydimethylsiloxane (PDMS) for optical detection applications. Alternative to other fiber-based sensor, the proposed optical sensor uses PDMS waveguide as the main sensing component. PDMS has excellent optical properties which is essential for bio-photonic detection, including highly optical transparency, good flexibility and high bio-compatibility. Uncured PDMS polymer is cast in a Teflon tubing to form the PDMS rod. Since the reflective index of PDMS is as high as 1.43, that the bare PDMS can be an optical waveguide while the reflective index of the surrounding media is smaller than 1.43. The cast PDMS waveguide is then connect with plastic optical fibers to form the proposed optical waveguide system. In order to improve the optical performance of the PDMS waveguide, a surface coating process is used to reduce the surface roughness of the PDMS waveguide. The measured insertion loss with and without performing the surface coating procedure is 1.14 and 1.71dB/cm, respectively. Once the PDMS waveguide is formed, Au nanoparticles (Au-Nps) were coated on the PDMS surface with the assistance of a positive charge polymer of PDDA to form an optical waveguide capable of localized SPR detection. In addition, an atmospheric plasma treating process is used to enhance the coating ratio and speed of Au-Nps. UV-VIS spectrum and the SEM observation of the Au-particle coated PDMS waveguide confirm that the plasma treatment process significantly improves the coating results of Au-Nps. Liquid samples with different refractive index were used to demonstrate the LSPR sensing ability of the fabricated optical waveguide. The label free DNA detection was demonstrated by the system. The thiolated single strand DNA was modify on the PDMS optical waveguide as a DNA probe and bound with target DNA by DNA hybridization. The detection limit is as low as 10 pM. This research provides a simple and fast fabrication method to fabricate waveguide-based LSPR sensors.

<p>The need for safe and functional implants has led to anincreased demand for improved biomaterials. The performance invivo depends on the interaction between the biologicalsurrounding and the surface of the material. By tailoring thesurface of a material with suitable bulk properties,biomaterials with an ability to interact with the biologicalsystem in a specific and controlled way are obtained. Siliconeelastomers have been used as biomaterials for several decades,but it is widely recognized that they are difficult to modifyby the conventional methods used for organic polymers due tothe partly inorganic structure of silicone.</p><p>This thesis presents a strategy to obtain siliconebiomaterials by covalent coupling of molecules to the surfaceusing silicon chemistry. The first step is to introduce Si-Hgroups onto the surface of silicone elastomers by plasmatreatment. The second step is to react a terminal double bondof a molecule with the formed Si-H group by a catalyzedhydrosilylation reaction. The coupled molecule may eitherprovide the desired properties itself, or have a functionalitythat is able to couple another molecule with suitablecharacteristics.</p><p>The influence of plasma treatment in hydrogen, argon andoxygen on the silicone elastomer was characterized by X-rayphotoelectron spectroscopy (XPS). To quantify the effect ofplasma treatment, the method of ternary XPS diagrams wasdeveloped. It was found that undesired silica-like layers wereformed under severe treatment conditions. Argon plasma at lowpower and short treatment time was the most suitable parametersetting. Subsequent hydrosilylation grafting ofallyltetrafluoroethylether, aminopropylvinylether andN-vinylformamide showed that it was possible to functionalizethe surface via a covalent link to the surface. The primaryamino groups introduced onto the surface were accessible forfurther coupling reactions. Heparin surfaces were obtained by acoupling reaction with the introduced amino groups.</p><p><b>Keywords:</b>Silicone elastomers, PDMS, XPS, ESCA, surfacemodification, plasma</p>

<p>Microcontact printing using elastomeric stamps is a technique used in finding new and efficient ways to produce biodetection chips. Microcontact printed, with poly(dimetylslioxane) (PDMS) stamps, patterns of antibodies have been evaluated using fluorescence microscopy, imaging ellipsometry and atomic force microscopy. Fluorescent conjugated polyelectrolytes form non-covalent molecular complexes with Immunoglobulin-γ type antibodies, antigen binding to the tagged antibody result in spectroscopic shifts. Four different conjugated polyelectrolytes (POWT, POMT, PTT, PTAA) in complex with human serum albumin antibodies (aHSA) have been tested with fluorescence spectroscopy. Complexes of POWT and aHSA gave rise to thelargest wavelength shift when exposed to human serum albumin.</p><p>Several types of commercially available fluorescent antibodies and antigens were used to test the specificity of microcontact printed antibodies to different antigen solutions. Using fluorescence microscopy it could not be shown that printed antibody patterns promote specific adsorption of corresponding antigen. It is proposed however that changed surface characteristics of the substrate due to PDMS residues transferred during printing is the main driving force behind antigen adsorption.</p><p>POMT - poly (3-[(s)-5-amino-5-methoxylcarboxyl-3-oxapentyl]-2,5-thiophenylenehydrochloride)</p><p>POWT - poly (3-(s)-5-amino-5-carboxyl-3-oxapentyl]-2,5-thiophenylenehydrochloride)</p><p>PTAA - polytiophene acetic acid</p><p>PTT - poly (3-[2,5,8-trioxanonyl] thiophene)</p>

In recent years, BioMEMS/NEMS have been primary elements associated with the research and development efforts in the bioengineering area. International and federal funding has effected an enormous increase in the development of state-of-the-art bioengineering and biomedical technologies. Most of the BioMEMS/NEMS related applications are associated with diagnostics, sensing and detection. Procedures for separation and manipulation of biological components play a paramount role in the function of these bioengineering mechanisms. This research was concerned with the development of a novel BioMEMS device for cell manipulation. The functioning of the device is based on the use of thermally responsive polymer networks, which differs dramatically from existing approaches. This approach is cost effective, requires low power and uses a minimal amount of on-device area, which makes it suitable for personal medical diagnostics and battle field scenarios. The device integrates the technologies associated with reversibly binding surfaces and dielectrophoresis, (DEP). The DEP field drives a sample into contact with a binding surface. This surface can be controlled to provide different levels of target selectivity. This system provides a separation strategy that does not suffer from fouling issues. The binding surfaces are fabricated from LCST polymers. The LCST polymers experience hydration-dehydration changes in response to temperature fluctuations. Therefore, separation efficiency can be "dialed in" as a function of temperature to prompt the selection of targets. Furthermore, size-exclusion "trenches" were patterned into the binding surfaces. The trenches permit the passage of the small objects in order to provide size-exclusion separations. In order to expand the discrimination size range from the micron to the submicron scale, two techniques for submicron patterning of cross-linked reversibly binding surfaces were investigated. The patterning techniques associated with electron-beam lithography and the combination of softlithography and a focused ion beam patterning were found to generate well-defined patterns that retained their thermo-responsiveness. The combination of DEP and reversibly binding surfaces for bio-particle manipulation is a significant contribution to microfluidic based separations in BioMEMS/NEMS. The developments associated with this research provide a novel technology platform that facilitates separations, which would be difficult to achieve by any other existing methods.