Abstract: We fabricate quasi-three-dimensional terahertz electric metamaterials by stacking multiple single-layer planar metamaterials fabricated on thin, flexible polyimide substrates. Terahertz time-domain spectroscopy is used to characterize their transmission properties, with which we obtain the frequency dependent complex effective dielectric functions. Increasing the number of layers reduces the resonant transmission minimum, while the extracted effective dielectric functions are independent on the number of layers. The results reveal that the real portions of the dielectric functions only show positive values, however, decreasing the thickness of the polyimide substrates, and thereby the spacing between the adjacent split-ring resonator layers, enables negative electric response.

Abstract—A flexible, smooth, and low profile conformal coat-ing was developed to accomplish the encapsulation of a micro-electromechanical system (MEMS) device that will be applied to sense the static pressure on aircraft during real flight testing. The encapsulant should be able to protect the MEMS device and the multichip module (MCM) from adverse environmental conditions, i.e., mechanical shock, temperature fluctuation, engine fuel and oil contamination, and moisture/mobile ion permeation. Presently, conventional packaging schemes for electronics cannot satisfy this specific outdoor application, and a new encapsulation combination has been designed in accord with the requirement of reliability without hermeticity (RWOH). A bi-layer structure was selected because of property limitations of a single material. Pliable elastomeric silicones, are typically flexible, water repel-lant, and abrasion resistant. The silicone encapsulant will be first applied to planarize the MEMS surface and function as durable dielectric insulation, stress-relief, and shock/vibration absorbers over a wide humidity/temperature range. To compensate for the deficiency of silicone on engine fuel/oil contamination, Parylene C is to be deposited afterward. This bi-layer coating can achieve excellent bulk properties, such as moisture and mobile ion barrier resistance, chemical compatibility, and electrical insulation char-acteristics. However, the poor adhesion of Parylene C to silicone greatly restricts its application. To address this problem, silane coupling agents were used as an adhesion promoter. Significant adhesion im provement was achieved by placing an interlayer silane coupling agent to provide interfacial bonding to the silicone elastomeric surface and the Parylene C film. Furthermore, a pos-sible mechanism of adhesion enhancement will also be presented in this study. Index Terms — Bi-layer conformal coating, micro-electro-mechanical system (MEMS), multichip module, Parylene C, reliability without hermeticity (RWOH), silane coupling agent, silicone elastomer. I.

Photosensitive polymers with photo-crosslinkable groups have gained a considerable interest in recent years owing to a wide variety of applications in the field of potoresists, photocurable coatings, microlithography, nonlinear optics, energy exchange materials, photosensitizers, etc.1-6 Among various photo-crosslinkable groups, α,β-unsaturated carbonyl unit known as cinnamoyl group have attracted particular attention due to its excellent photoreactivity at UV absorp-tion wavelength.7-11 Here, cinnamoyl group either in the back-bone or side chain of the polymer can easily be produced by crosslinking reaction through [2pi+2pi] cycloaddition of the carbon-carbon double bond upon irradiation with UV light.12-14 In this paper, we report the synthesis and characterization of a new photo-crosslinkable aromatic polyester with cinnamoyl group onto polymer backbone.

ech.(2009)P02031

(Dr. rer. nat.)

Photophysical studies of probes bound to cross-link junctions in poly(dimethy1 siloxane) elastomers and nanocomposites

Abstract not found

Si substrates

ABSTRACT: Effects of chemical structure changes on the thermal, mechanical, and crystalline properties of rigid rod epoxy resins have been studied for azomethine epoxy, biphenol epoxy, and tetramethyl biphenol epoxy. Rigid rod epoxies have exhibited better properties than those of the flexible bisphenol A epoxy. The chemical structures of both rigid rod epoxy and curing agent control the properties of cured rigid rod epoxies. When a flexible curing agent (methyl cyclohexane 1,2-dicarboxylic anhydride) was used, the chemical structure of rigid rod epoxy has dominated effects on the properties. Thus, the azomethine epoxy has shown the best thermal and mechanical properties among three rigid rod epoxies. While a rigid curing agent (sulfanilamide) was used, the physical properties of cured epoxies are not only dependent on the chemical structures of epoxies but also on the ease of formation of ordered network. Among the cured rigid rod epoxies, only the biphenol epoxy cured by sulfanilamide exhibits a liquid crystalline network. It has the highest glass transition temperature (219°C) and the lowest coefficient of thermal expansion (20.8 mm/m°C). However, the most thermal stable system is azomethine epoxy cured with sulfanilamide. It has a weight loss (39%) at 450°C. Their excellent thermal and mechanical properties of rigid rod epoxies are useful in composites, printed wiring boards, integrated circuit encapsulations, etc. © 2000 John