Transcript Materials For Microfluidics

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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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 layergives 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.
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References
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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.