Christopher E. Dubé

Fluid damping in resonant flexural plate wave device

Fluid damping models are developed for resonant (standing wave) flexural plate wave (FPW) devices, which are rectangular plates or diaphragms with structural layers, a piezoelectric layer, and interdigitated conducting combs for driving and sensing. This configuration is often used in micromechanical chemical, biological, or nonvolatile residue sensors. Where much of the previous work on fluid effects in FPW devices focused on delay lines, this effort investigates resonant devices both analytically and experimentally. The fluid model is based on closed-form solution of a wide beam vibrating into a semi-infinite fluid volume and is mated directly into the beam equation. While the fluids pressure versus wave motion solution has been reported previously, the application to the resonant FPW is mathematically rigorous and leads to a greater understanding of the FPW damping regimes. Frequency responses of FPW devices constructed from silicon with deposited piezoelectric aluminum nitride and operating in water and alcohol compared well with analytic results with some discrepancies noted.

Micromachined silicon plates for sensing molecular interactions

A micromachined surface stress sensor based on a thin suspended crystalline silicon circular plate measures differential surface stress changes associated with vapor phase chemisorption of an alkanethiol self-assembled monolayer. The isolated face of the suspended silicon plate serves as the sensing surface treated with a receptor layer sensitive to a target molecule, in this case Au(111). Chemisorption of an alkanethiol on the gold coated silicon surfaces results in plate bending. Plate displacements, measured with a phase scanning interferometer, indicate a differential surface stress change

A Si-based FPW sensor array system with polymer microfluidics integrated on a PCB

\Delta \sigma_s

Electromagnetically-actuated microfluidic flow regulators and related applications

=-0.72 +/- 0.02 N m(-1) for 1-dodecanethiol.

Integrated electrofluidic system and method

Many methods for fabricating structures for microfluidic-based sensors have been developed in recent years. However, little has been reported on effective methods for integrating these structures into electronic systems for analysis and fluidic delivery. This paper describes a straightforward and versatile fabrication platform for polymer microfluidics that readily accommodates integration with silicon-based sensors, printed circuit, and surface mount technologies. In particular, we have demonstrated a novel system for distributed fluid delivery to a flexural plate wave (FPW) chemical/biological sensor where micromachined fluidic components are combined in a single package with silicon die, multilayer printed circuit board, and surface mount electronics. In the same fabrication platform, we have demonstrated temperature control of the sensor with 0.1/spl deg/C precision using integrated metal thin-film heater and sensor elements. This is an important capability for FPW sensors to compensate for temperature-induced drift. We present results for the on-board microfluidic system where the sensor is used to detect changes in the composition of the supplied fluid.