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This work presents recent progress in the area of organic photorefractive polymer composites. These materials have been previously shown to be a suitable medium for dynamic holographic displays, with multiple colors and single frame writing times on the order of seconds. However, these materials still require large electric fields and high intensity lasers to function effectively. Recent advancements in improving these areas are discussed, including a review of the history and state-of-the-art in photorefractive polymer composites.The addition of electron traps via low loading of the electron-transporting molecule Alq3 is shown to dramatically improve the diffraction efficiency and reduce the required field. The grating formation also proceeds faster by more than one order of magnitude, leading to an increase in sensitivity by a factor of 3. The dynamics of these materials also show evidence of competing gratings indicative of bipolar charge transport and trapping.The addition of an amorphous polycarbonate (APC) buffer layer is reported to have a similar effect on the steady-state diffraction efficiency, and the further doping with a fullerene derivative (PCBM) allows a 3x increase in the efficiency in the reflection geometry, which is normally poor due to the small grating spacing. These composites reveal the fundamental limits of the reflection geometry, based on the physics of high frequency gratings. A reversal in the direction and increase in the magnitude of the two-beam coupling energy transfer is also observed.The use of interdigitated coplanar electrodes, instead of the standard uniform electrodes in a parallel-plate geometry, is shown to result in large diffraction efficiency with symmetric writing beams due to the increased projection field. The efficiency is similar to that achieved in the standard samples with large slant angles and much better than those geometries typically used in applications, with the benefit that the writing beams do not have to be slanted with respect to the sample normal. Different electrode widths are examined and the trade-offs discussed. This device makes beam injection simpler and allows one to bring the benefits of highly slanted geometries, common to small area setups, to the large-area applications.

In this thesis, a novel technique for measuring photoacid generation kinetics in chemically amplified photoresists was developed that utilizes capacitance measurements from interdigitated electrodes. In this technique, a chemically amplified photoresist is first coated onto the interdigitated electrode sensors. Then, capacitance measurements are recorded from the sensor as the photoresist is exposed to UV radiation. As acid is generated in the film during exposure, the net dielectric constant of the resist film changes, resulting in a change in the capacitance measured from the IDE sensor. By properly analyzing the observed capacitance response to exposure, it is possible to determine the kinetic rate constant for photoacid generation, or Dill C parameter. The discussion in this thesis describes four major areas of work performed. First, the basic development of the Dill C measurement technique and data analysis algorithm is described. Second, potential complications due to relative humidity changes, spin coating problems, and ambient base contamination are investigated. Next, the discussion turns to two key improvements to the measurement technique: the use of multi-frequency measurements to increase the capacitance signal, and the development of a normalized capacitance expression for improved data analysis. Finally, the effects of two critical components of chemically amplified resist solutions upon the technique are studied: protecting groups and background base quenchers.

A numerical simulation study for an interdigitated micro-channel PEM fuel cell is presented. Hydrogen gas is supplied to the anode and air is supplied to the cathode. The fuel cell outer surfaces are maintained at a constant temperature. The SIMPLEC algorithm is employed in a control volume numerical scheme. The outflow boundary conditions are specified to all transport equations except that an outlet pressure is specified to the momentum equation. Results are compared and show good agreement with the experimental data. The effects of the mass flow rate, the outlet pressure and the cell surface temperature on the cell performance are studied. The results can provide reference for fuel cell design.

The dielectric properties of polymeric thin films (100-200 nm) are hard to measure with the standard approaches as the samples aren't free standing necessitating a supporting substrate. Consequently, a planar interdigitated sample holder has been designed to hold the thin film where the polymeric capacitance was derived from the passing fringing fields. The electrodes were fabricated by creating 120 nm trenches in a SiO2/Si wafer; 20 nm Cr was deposited as an adhesion layer prior to the deposition of Cu by thermal evaporation. The electrical measurements were implemented using HP 4294A and a probe station. Devices of 20 to 70 fingers were measured and the results were compared to the analytical and finite element simulation. At 10 KHz, the total measured capacitance of a 20-finger device was about 8 pF with 3 % represented the polymeric contribution. The measurements differed from the calculations or finite modeling results by about 12%.

The objective of this thesis is to develop a complex dielectric properties sensor using interdigitated capacitor (IDC) structure. IDCs are easy to fabricate and because of its planar structure, it can be easily integrated with other sensing components and signal processing electronics. The design, fabrication, modeling, and testing of IDC sensors are presented in this thesis. Design parameters and their influence on sensor's output signals are discussed. Previous IDC models are reviewed and the limitations are studied. A new equivalent circuit model based on the fringing electric field distribution and a novel iterative data extraction algorithm combining Finite-Element Method (FEM) and the equivalent circuit model is studied. Results suggest that the algorithm can accurately extract relatively low dielectric constant and conductivity of material under test (MUT) from measured impedance data. / text

According to the previous experimental fact that an interdigitated single PEMFC has a better performance than other flow type single PEMFC, therefore this research is aimed to predict a two-cell stack interdigitated PEMFC via a numerical simulation. Investigation the effects of the cell temperature, the cell operating pressure, the fuel flow rate and the air flow rate are performed. This research can provide design reference for application of interdigitated PEMFC stack.

Grain storage is an essential part of the food production chain. Therefore, pre- venting grain deterioration is a key issue in a grain storage system. There are several causes for spoilage, all resulting in grain quality and quantity loss. One approach to detect incipient spoilage is by detecting the produced volatiles. In the past, many sensors for detecting volatiles have been developed and are used in industry. However, most of the commercial gas sensors are bulky with high power consumption, mainly limited in range of operating temperature, or require a restricted control over temperature and humidity. This thesis describes the design, fabrication and evaluation of a gas sensor capable of detecting volatiles and considers the potential use of polymer- based sensors. Conductive polymer-based sensors have been reported sensitive to a wide range of volatiles but are commonly evaluated under a controlled environment. Conventional sensor reproducibility and repeatability are also a concern due to the difficulties associated with polymer composite film preparation. In addition, current studies have not fully explored sensor properties in response to humidity, a common factor in any environment, and a variable parameter in grain storage facilities. Moreover, these sensors suffer from ambient temperature dependency as they work based on partitioning mechanism. To enhance sensor performances and eliminate the temperature dependency, a new sensor structure is proposed. The new design uses standard lithography process to fabricate a thermally isolated cantilever containing interdigitated electrodes and a micro-heater to efficiently heat and maintain a constant temperature throughout the interdigitated electrodes. This structure eliminates sensor response drifts caused by ambient temperature variations. Capacitive measurements are performed as the means of volatile detection, which simplify the use of polymers due to the absence of conductive filler and the challenges associated with it. Frequency spectroscopy provides additional information regarding the presence of volatiles compared to conventional resistive sensors, since mechanisms other than swelling are involved. Moreover, frequency and temperature modulations can be employed to further enhance sensor performance, enabling the use of a reduced number of sensors in a sensor array.

Grain storage is an essential part of the food production chain. Therefore, pre- venting grain deterioration is a key issue in a grain storage system. There are several causes for spoilage, all resulting in grain quality and quantity loss. One approach to detect incipient spoilage is by detecting the produced volatiles. In the past, many sensors for detecting volatiles have been developed and are used in industry. However, most of the commercial gas sensors are bulky with high power consumption, mainly limited in range of operating temperature, or require a restricted control over temperature and humidity. This thesis describes the design, fabrication and evaluation of a gas sensor capable of detecting volatiles and considers the potential use of polymer- based sensors. Conductive polymer-based sensors have been reported sensitive to a wide range of volatiles but are commonly evaluated under a controlled environment. Conventional sensor reproducibility and repeatability are also a concern due to the difficulties associated with polymer composite film preparation. In addition, current studies have not fully explored sensor properties in response to humidity, a common factor in any environment, and a variable parameter in grain storage facilities. Moreover, these sensors suffer from ambient temperature dependency as they work based on partitioning mechanism. To enhance sensor performances and eliminate the temperature dependency, a new sensor structure is proposed. The new design uses standard lithography process to fabricate a thermally isolated cantilever containing interdigitated electrodes and a micro-heater to efficiently heat and maintain a constant temperature throughout the interdigitated electrodes. This structure eliminates sensor response drifts caused by ambient temperature variations. Capacitive measurements are performed as the means of volatile detection, which simplify the use of polymers due to the absence of conductive filler and the challenges associated with it. Frequency spectroscopy provides additional information regarding the presence of volatiles compared to conventional resistive sensors, since mechanisms other than swelling are involved. Moreover, frequency and temperature modulations can be employed to further enhance sensor performance, enabling the use of a reduced number of sensors in a sensor array.