No abstract

Wehave developed a microfabricated flow-through impedance characterization system capable of performing AC, multi-frequency measurements on cells and other particles. The sensor measures both the resistive and reactive impedance of passing particles, at rates of up to 100 particles per second. Its operational bandwidth approaches 10 MHz with a signal-tonoise ratio of approximately 40 dB. Partide impedance is measured at three or more frequencies simultaneously, enabling the derivation of multiple particle parameters. This constitutes an improvement to the well-established technique of DC particle sizing via the Coulter Principle. Human peripheral blood granulocyte radius, membrane capacitance, and cytoplasmic conductivity were measured (r = 4.1 f.!m, Cmem = 0.9 f.!F/cm 2 , O"int = 0.66 S/m) and were found to be consistent with published values.

The morphological evolution of lithographically defined cracklike flaws in glass and glass-containing ceramics was studied at elevated temperatures. The systems studied have glass contents from 100 to approximately 0.5 vol%, providing insight to the contribution of viscous flow of the glass to crack healing over a range of glass contents spanning many industrial ceramics. Healing behavior is found to be controlled by viscous flow of glass in all cases except the lowest glass content, for which significant mass transport is only accomplished by diffusional mechanisms. This implies a change of mechanism below some critical glass content.