A Mems Body Fluid Flow Sensor
Ellis Meng, Sascha Gassmann, and Yu-Chong Tai

To achieve in vitro flow rate measurements of biological fluids in such tasks as hematological studies and urinalysis, a MEMS flow sensor has been developed. Flow sensing is achieved by measuring the forced convective heat transfer from a thermal sensing element to the fluid. Currently, fluid flow down to 10 ml/min can be detected. (full report)

Flexible Parylene-Valved Skin for Adaptive Flow Control
T. Nick Pornsin-Sirirak, Matthieu Liger, Yu-Chong Tai, Steve Ho, Chih-Ming Ho

This research describes the first work of using wafer-sized flexible parylene-valved actuator skin (total thickness ~ 20 _m) for micro adaptive flow control. The check-valved actuator skin features vent-through holes with tethered valve caps on the membrane to regulate pressure distribution across the skin. The skins were integrated onto micro-aerial-vehicle (MAV) wings that were tested in the wind tunnel for aerodynamic evaluation. The test result has shown a very significant effect on the aerodynamic performance. Compare to the reference wings (no actuators), both the lift and thrust of the check-valved wings are improved by more than 50%. This is the first experimental result to demonstrate that the application of MEMS actuator skins for flow control is very promising. (full report)

Residual Stress in Thin-Film Parylene-C
Theodore A. Harder, Tze-Jung Yao, Qing He, C.Y. Shih and Y.-C. Tai

Parylene is an important material for Bio-Microelectromechanical Systems. Understanding parylene's material properties is critical to the fabrication of complex Microfluidic devices. We have found that the process history of the device has a significant effect on the mechanical properties of Parylene. (full report)

Dielectric Charging Effect on Parylene Electrostatic Actuators
Tze-Jung Yao, Ken Walsh and Yu-Chong Tai

We report here for the first time a characterization of the dielectric charging effect on Parylene electrostatic actuators. High resistivity dielectrics in-between air gaps can cause undesired charging effects when operating as electrostatic sensors/actuators at voltages as low as tens of volts. This undesired effect can either lower the sensitivity of the sensor or increase the pull-in voltage of the actuator. Moreover, the actuator operating at high voltage could even suffer "bounce-back and pull-in voltage drift problems. Thus, to fully utilize dielectrics in electrostatic devices, careful attention must be given on selecting the ideal values for operating voltage and resistivity of the dielectrics. (full report)

Underwater Shear Stress Sensor
Yong Xu, Fukang Jiang, Qiao Lin, Jason Clendenen, Steve Tung and Yu-Chong Tai

A micromachined, vacuum-cavity insulated, thermal shear stress sensor is developed for underwater applications. The two major challenges for underwater application, namely the waterproof coating and pressure sensitivity, are specially studied for our device. (full report)

A Thermopneumatic Microfluidic System
Charles Grosjean, Xing Yang, and Yu-Chong Tai

A self-contained planar microfluidic system using thermopneumatic actuation has been demonstrated. Using a novel suspended silicon island heater fabricated by DRIE, and a precision machined acrylic fluidic substrate with a matching silicone rubber membrane, a system of channels, valves, and a pump has been demonstrated with self-contained actuation using air as a working fluid. (full report)