Inorganic Materials ForBiomems

Anne Samuel

Inorganic Materials

Materials used for micropumps and valves Thin-Film Shape Memory Alloy(NiTi)

Actuated Micropump NiTi/Si Diaphragm Micropump Micromachined pump based on thick-film

piezoelectric actuation.

Thin-Film Shape-Memory Alloy Actuated Micropump

Shape memory alloys are ones which undergoes

phase transformation from one phase(austenite)

to an another phase( Maternsite). Used one way shape memory effect (OWSME) for

actuation. Two actuation configurations to perform actuation-

Polyimide-Spring-Biased actuator(Polyimide + TiNi) & Complementary Actuator ( TiNi+TiNi).

NiTi/Si Diaphragm Micropump

Micropump actuated by NiTi/Si composite diaphragm.

The recoverable force of NiTi thin film and biasing force of silicon membrane allows reciprocating motion of the pump.

Structure of a unit SMA/substrate bimorph.

NiTi/Si Micropump

Analysis of the actuation mechanism. Thermal expansion coefficients of Si and

SMA are different. Depending on temperature, the bimorph

structure will deform or be flat.

Thick-film Piezoelectric Actuation

Micropump with thick film /silicon micromachined hybrid actuation.

Actuation based on the flexure of screen printed PZT layer on Si membrane.

Schematic of hybrid actuated micropump. Pump consists of top electrode, bottom

electrode and PZT layer in the middle.

Thick-film Piezoelectric Actuation

Experiment with different bottom electrodes. To find high dielectric values of PZT layer-

gives good mechanical acutation performance. It was found that Au Cermet and evaporated Pt

thin film gives good dielectric constant. Candidate in medicine as a cheap disposable

pump for drug dispensing.

References

Bernard.W, Kahn.H et.al. “ Thin-film shape memory alloy actuated micropumps”. Journal of Microelectromechanical system.1998. Vol 7. PP 245-251.

Koch.H, Harris.N et.al. “A novel micromachined pump based on thick-film piezoelectric actuation”. Sensors and Actuators, 1998. Vol 70. PP 98-103.

Xu.D, Wang.Li, et.al. “Characteristics and Fabrication of NiTi/Si diaphragm micropump”. Sensors and Actuators, 2001. Vol 93. PP 87-92.