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Inorganic Materials For Biomems. 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.
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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.