Lecture 22 Mechanical Microsystems

Lecture 22 Mechanical Microsystems - Mechanical Actuators...

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Mechanical MEMS Dr. Bruce K. Gale Fundamentals of Micromachining Mechanical Actuators • Actuation mechanisms: – electrostatic = electrostatic attraction of charged plates – thermal = expansion of solids or fluids – shape memory alloy = considerable change in length – pneumatic/hydraulic = fluid pressure – piezoelectric = electrically induced strain – magnetic –chem ica l – biological Electrostatic Actuators • Based on attraction of two oppositely charged plates • Typically low power • Simple to fabricate • Coulomb’s law: 2 2 1 4 1 x q q F o r elec ε πε = Electrostatic Actuation • Cantilever Actuators – electrostatic force –t ip de f lec t ion 2 ) ( 2 ) ( x d d V x q o ε dx x wq x L EI x d T ) ( ) 3 ( 6 ) ( 2 = δ + + + + + + + + + + _ _ _
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Electrostatic Actuation • Fabrication – polysilicon with sacrificial oxide – electroplated metal with sacrificial organic layer – sputtered metal with sacrificial organic layer • Torsional Actuators – dual deflection electrodes – small deflection Torsional spring for mirror application Electrostatic Actuation • Comb Drives – use large number of electrostatically actuated fine “fingers” – attractive force is mainly due to fringing fields – generate large movements Electrostatic Actuation • Rotary Micromotors – use freely moving central rotor with surrounding capacitive plates – up to 300,000 rpm – up to 300 V – Fabrication: • polysilicon/oxide
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This note was uploaded on 11/16/2011 for the course MSE 5960 taught by Professor Douglas during the Fall '04 term at University of Florida.

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Lecture 22 Mechanical Microsystems - Mechanical Actuators...

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