For this thesis, the use of Liquid Crystal Polymer (LCP) as a system-level substrate and packaging material is investigated. Early in the research, recipes for fabricating on LCP were developed. With this knowledge, RF components were able to be fabricated. These devices include filters, antennas, phase shifters, and RF MEMS switches. To investigate the potential of using LCP as a system-level material, packaging properties and robustness were tested. This research demonstrated that LCP could be used to package something as small and delicate as an individual switch or as large as a 4-inch wafer. In addition, it was shown that MEMS switches could survive well over a hundred million cycles. This demonstrated that LCP could be used to create reliable, high performance systems. The culmination of this research was used to create two variations of a communication module. The first device was fabricated on one layer and a multi-layer approach was taken for the other device. These modules needed to be low-cost, low-loss, flexible, and capable of beam steering. This technology can be used for communication, sensing, detection, and surveillance for a broad scope of applications. To this date, they are by far the most sophisticated SOP on LCP ever achieved. This technology can be further developed to include more functionality, smaller size, and even better performance.

In this thesis we synthesize two organic materials, one is discotic liquid crystal Acid-6, and the other is novel discotic liquid crystal polymer DLC-PAM. After demonstrating the molecular structures of Acid-6 and DLC-PAM by FT-MS, 1H-NMR and FT-IR, we use the two materials as photo-sensitized dyes for dye-sensitized solar cells(DSSCs) and manufacture two kinds of cells. We use polyacrylamide(PAM) as main chain of the novel discotic liquid crystal polymer DLC-PAM and graft the discotic liquid crystal monomer Acid-6 onto PAM by chemical synthesis. DLC-PAM belongs to side-chain liquid crystal polymer, and it can show the properties of it¡¦s discotic liquid crystal function. One of the properties is absorption of visible light. By observing the UV-Vis spectrum, we can realize the absorption band is located between 200 ~ 450 nm and confirm that it is able to be a photo-sensitized dye. Another property of discotic liquid crystal is the self-assembly ability, the moleculars can assemble into hexagonal columnar structure by themselves, and the property enable discotic liquid crystal to have better mobility. In this part, we can demonstrate DLC-PAM and Acid-6 really have hexagonal columnar structure by X-ray diffractmeter. After qualitative demonstrating and optical analysis, we use DLC-PAM and Acid-6 as photo-sensitized dyes for DSSCs and manufacture two kinds of cells successfully. The more photocurrent occur when the two DSSCs are woking. Besides, the two DSSCs have good performance on power conversion efficiency which can achieve 0.047 % for DLC-PAM and 0.364 % for Acid-6. Therefore, in this research we prove that DLC-PAM and Acid-6 are able to be photo-sensitized dyes for DSSCs and successfully demonstrate that using the two materials to manufacture DSSCs is feasible.

A number of high performance fibres (aramid, PBZT and PBO) spun from liquid crystal polymer solutions were examined in this work. In particular, a thorough investigation of the mechanical response of these fibres under tensile and compressive deformations was carried out. The major experimental tool employed was the technique of Laser Raman Spectroscopy. It was found that stress-induced changes of these fibres at molecular level are proportional to the macroscopic deformation applied. This correlation is unique for the fibres. A method for converting spectroscopic data to predicted stress-strain curves in tension and compression was proposed. An estimation of their compressive strength was derived and an understanding of the nature of their compressive failure was discussed. The adhesion of these fibres to epoxy resin was also investigated by monitoring in situ the interfacial stresses developed along the interface/interphaseo f model single fibre composite coupons. The strength of the interfacial bond was measured. The effect of various parameters such as fibre modulus, fibre diameter and fibre nature upon the interfacial strength of the various systems was evaluated. The mechanisms of stress transfer along with the nature of interfacial damage was examined accurately. It was found that the major parameter controlling the above mechanisms was interfacial yielding in shear. A numerical appoximation (using Finite Element Analysis) was employed in order to evaluate the experimental results. Finally, general conclusions concerning the performance of these fibres were drawn.

The development of environmental continuous monitoring of physicochemical parameters via portable small and inexpensive instrumentation is an active field of research as it presents distinct challenges. The development of a PCB MEMS-based inexpensive CTD system intended for the measurement of environmental parameters in natural waters, is presented in this work. Novel PCB MEMS fabrication techniques have also been developed to construct the conductivity and temperature transducers. The design and fabrication processes are based on PCB MEMS technology that combines Cu-clad liquid crystal polymer (LCP) thin-film material with a direct write photolithography tool, chemical etching and metallization of layers of electroless nickel, gold, and platinum. The basic principles of a planar four-electrode conductivity cell and the resistive temperature device are described here as well as the integration and the packaging of the microfabricated sensors for the underwater environment. Measurement results and successful field evaluation data show that the performance of the LCP thin-film microsensors can compete with that of conventional in-situ instruments.

This dissertation shows a detailed investigation on reconfigurable low profile antennas using tunable high impedance surfaces (HIS). The specific class of HIS used in this dissertation is called a frequency selective surface (FSS). This type of periodic structure is fabricated to create artificial magnetic conductors (AMCs) that exhibit properties similar to perfect magnetic conductors (PMCs). The antennas are intended for radiometric sensing applications in the biomedical field. For the particular sensing application of interest in this dissertation, the performance of the antenna sub-system is the most critical aspect of the radiometer design where characteristics such as small size, light weight, conformability, simple integration, adjustment in response to adverse environmental loading, and the ability to block external radio frequency interference to maximize the detection sensitivity are desirable. The antenna designs in this dissertation are based on broadband dipole antennas over a tunable FSS to extend the usable frequency range. The main features of these antennas are the use of an FSS that does not include via connections to ground, their low profile and potentially conformal nature, high front-to-back radiation pattern ratio, and the ability to dynamically adjust the center frequency. The reduction of interlayer wiring on the tunable FSS minimizes the fabrication complexity and facilitates the use of flexible substrates. This dissertation aims to advance the state of the art in low profile tunable planar antennas. It shows a qualitative comparison between antennas backed with different unit cell geometries. It demonstrates the feasibility to use either semiconductor or ferroelectric thin film varactor-based tunable FSS to allow adjustment in the antenna frequency in response to environment loading in the near-field. Additionally, it illustrates how the coupling between antenna and HIS, and the impact of the varactor losses affect the antenna performance and it shows solutions to compensate these adverse effects. Novel hybrid manufacturing approaches to achieve flexibility on electrically thick antennas that could be transitioned to thin-film microelectronics are also presented. The semiconductor and ferroelectric varactor-based tunable low profile antennas demonstrated tunability from 2.2 GHz to 2.65 GHz with instantaneous bandwidths greater than 50 MHz within the tuning range. The antennas had maximum thicknesses of λ/45 at the central frequency and front to back-lobe radiation ratios of approximately 15dB. They also showed impedance match improvement in the presence of a Human Core Model (HCM) phantom at close proximity distances of the order of 10-20 mm. In addition, the use of thin film ferroelectric Barium Strontium Titanate (BST) varactors in the FSS layer enabled an antenna that had smaller size, lower cost and less weight compared to the commercially available options. The challenging problems of fabricating robust flexible antennas are also addressed and novel solutions are proposed. Two different types of flexible antennas were designed and built. A series of flexible microstrip antennas with slotted grounds which demonstrated to be robust and have 42% less mass than typically used technologies (e.g., microstrip antennas fabricated on Rogers® RT6010, RT/duroid® 5880, etc.); and flexible ferroelectric based tunable low profile antennas that showed tunability from 2.42 GHz to 2.66 GHz using overlapping metallic plates instead of a continuous ground plane. The bending test results demonstrated that, by placing cuts on the ground plane or using overlapping metallic layers that resemble fish scales, it was possible to create highly conductive surfaces that were extremely flexible even when attached to other solid materials. These new approaches were used to overcome limitations commonly encountered in the design of antennas that are intended for use on non-flat surfaces. The material presented in this dissertation represents the first investigation of reconfigurable low profile antennas using tunable high impedance surfaces where the desired electromagnetic performance as well as additional relevant features such as robustness, low weight, low cost and low complexity were demonstrated.

Significant potential for plastic hypodermic needles exists as an alternative to current steel needles, especially in developing regions where proper needle disposal is problematic. Needle reuse causes tens of millions of hepatitis and HIV infections each year. Plastic needles may reduce reusability and increase the opportunities for safe disposal. Plastic needles also will help with medical waste disposal, by removing metal from the waste stream, hence making it easier to reprocess needles and syringes into useful products such as car battery cases and pails. This thesis presents the design and testing of one type of plastic hypodermic needle. The buckling and penetration characteristics of the needles were modeled and analyzed analytically and by finite element analyses. Experimental penetration tests using steel and plastic hypodermic needles and skin mimics, specifically polyurethane film and pig skin, were performed to determine penetration and friction forces. Penetration tests also were conducted to determine whether the needles could penetrate butyl rubber stoppers that cover drug vials. Various lubricants, including silicone oil and a medical grade silicone dispersion, were also used. In addition, the needles underwent perpendicular bending tests and cannula stiffness tests. Finally, fluid flow tests were conducted to determine fluid flow rates through the needles. Experimental results were compared to each other and finite element analyses and discussed. The research presented in this thesis demonstrates that with further design modifications, plastic needles may become suitable for mass replacement of steel needles, thus helping to eradicate the many health and environmental risks brought upon by steel needles.

No description available.

No description available.

No description available.

No description available.