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Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] triblock copolymer and a low‐volatility, midblock‐compatible mineral oil have been investigated here to ascertain the effects of composition on TPEG morphology, and temperature on mechanical properties. Cryofracture‐replication transmission electron micrographs reveal the existence of spheroidal bumps due to copolymer micelles, as well as a network of irregularly shaped, high‐aspect‐ratio features. Since the density of this network decreases with increasing oil concentration, these features are attributed to copolymer grain boundaries. Micellar periodicities are discerned from small‐angle X‐ray scattering as a function of copolymer concentration and compared with previously reported data from related systems. Dynamic rheological tests performed up to 140°C indicate that the linear viscoelastic regime for these TPEGs decreases with both increasing copolymer concentration and temperature. A concentration‐dependent thermal transition, signified by an abrupt reduction in the dynamic elastic modulus (G′), has also been identified.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2513–2523, 1998

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The design of piezoelectric resonating structures was investigated for generating acoustic streaming which may be used for cooling microelectronic components. The vibration characteristics of different piezoelectric structures were simulated by the finite element method and validated with analytical approaches. Considering the product of resonance frequency and dynamic tip deflection as a performance merit, the effects of length and location of the actuators as well as the boundary conditions were analyzed for four different piezoelectric resonator designs. Results show that there exist optimal length and location of actuators on the passive structures.