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III Semester M.E. (Power Electronics) Degree Examination, January 2015 (2K8 Scheme) PE EL – 33 : MICRO ELECTRO MECHANICAL SYSTEMS Time : 3 Hours

Max. Marks : 100

Instruction : Answer any five full questions. 1. a) What are MEMS ? With a functional diagram, explain the components of a MEMS system.

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b) Discuss the classification of MEMS with principle of operation.

14

2. a) With a neat sketch, explain the micropressure sensor using vibrating beam. b) Explain the following : i) Seebeck effect ii) Peltier effect iii) Shape memory effect.

10

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3. a) What are microactuators ? With neat sketches, describe the following methods of microactuation. i) Electrostatic actuation ii) Piezoelectric actuation. (5+5) b) Describe the case studies of the following : i) Micro valve ii) Micropump.

(5+5)

4. a) With relevant scaling theory, discuss the operation of a micromotor and a macromotor.

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b) Calculate the amplitude and frequency of vibration of a 10 mg proof mass suspended from a spring with spring constant k = 6 ×10–5 N/m. The vibration of the mass is initiated by a small pull of the mass downward by an amount δunit = 5μm .

8 P.T.O.

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5. a) What is microaccelerometer ? With neat sketches, explain the theory of its operation.

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b) With a neat sketch, explain the operation of a linear micromotor.

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6. a) What is micromachining ? With neat step-by-step sketches, describe the surface micromachining process. b) What is etching ? Compare dry etching with wet etching.

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7. Write short notes on the following : a) LIGA process.

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b) Role of photoresist.

5

c) Si as substrate material for MEMS.

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