A hybrid PZT-silicon microvalve

A low-voltage, low-power microvalve for compact battery-powered portable microfluidic platforms is designed, fabricated and experimentally characterized. The microvalve employs laser-machined piezoelectric unimorphs mechanically linked to surface micromachined nickel structures anchored on corrugated Si/sub x/N/sub y/-Parylene composite membrane tethers. The Parylene layer also serves as a compliant sealing layer on the valve seat for reducing the leakage in the off state. A mechanical linking process to connect the bulk piezoelectric unimorphs to micromachined diaphragms in a self-aligned manner has been developed. The design enables large strokes (2.45 /spl mu/m) at low-actuation voltages (10 V) consuming a comparatively low switching energy (678 nJ). The dependence of the measured flow rates on the modulated clearance over the orifice was found to be in good agreement with the theory of laminar flow in the low (1-100) Reynolds number regime. The microvalve was experimentally characterized for both gas and liquid flows. For example, at 10 V unimorph actuation, a gas flow rate of 420 /spl mu/L/min at a differential pressure of 9.66 kPa was measured. The off-state leakage rate for 0 V actuation is estimated to be 10-20 /spl mu/L/min. Typical flow rates with pulse width modulated (PWM) actuation with 50% duty cycle at 20 V/sub pp/ (1 kHz) were measured to be 770 /spl mu/L/min at 6.9 kPa for gases and 2.77 /spl mu/L/min at 4.71 kPa for liquids.

[1]  U. Bonne,et al.  Micromachined silicon microvalve , 1990, IEEE Proceedings on Micro Electro Mechanical Systems, An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots..

[2]  J. G. Smits.  Piezoelectric micropump with three valves working peristaltically , 1990 .

[3]  Michael Allan Huff,et al.  Silicon micromachined wafer-bonded valves , 1993 .

[4]  R. Zengerle,et al.  The selfpriming VAMP , 1997, Proceedings of International Solid State Sensors and Actuators Conference (Transducers '97).

[5]  T. N. Stevenson,et al.  Fluid Mechanics , 2021, Nature.

[6]  Masayoshi Esashi,et al.  Microflow devices and systems , 1994 .

[7]  L. Leal,et al.  Laminar flow and convective transport processes : scaling principles and asymptotic analysis , 1992 .

[8]  Amit Lal,et al.  In-channel micromechanical drag flow sensor with electronic readout , 2003, The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE.

[9]  A remotely actuated magnetic actuator for microsurgery with piezoresistive feedback , 2002, 2nd Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine and Biology. Proceedings (Cat. No.02EX578).

[10]  Choonsup Lee,et al.  Normally-closed, leak-tight piezoelectric microvalve under ultra-high upstream pressure for integrated micropropulsion , 2003, The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE.

[11]  J.G. Smits,et al.  The constituent equations of piezoelectric heterogeneous bimorphs , 1991, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[12]  H. Jerman,et al.  Electrically-activated, micromachined diaphragm valves , 1990, IEEE 4th Technical Digest on Solid-State Sensor and Actuator Workshop.

[13]  Yu-Chong Tai,et al.  Robust parylene-to-silicon mechanical anchoring , 2003, The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE.

[14]  Corrugated silicon nitride membranes as suspensions in micromachined silicon accelerometers , 1996 .

[15]  J. L. Steyn,et al.  A piezoelectric microvalve for compact high-frequency, high-differential pressure hydraulic micropumping systems , 2003 .

[16]  U. Schaber,et al.  Pneumatic Silicon Microvalves with Piezoelectric Actuation , 2001 .