1.3 MicroElectroMechanical structures, devices and systems :

 
MicroElectroMechanical Systems (MEMS) are based on the silicon IC technologies and include, in addition to the electronic components like resistors, capacitors, diodes, transistors, mechanical structures which are flexible and can be moved by magnetic, electric, and thermal fields. MEMS systems are becoming increasingly important as these are slowly replacing the silicon based sensors in measuring instruments and control systems. MEMS have demonstrated compatibility with silicon VLSI microelectronics technologies. All labs around the world that were involved with silicon device/technology have modified the scope of activity of their silicon program to include MEMS.

Present MEMS Activity at IIT Bombay :

I have recently joined IIT at Bombay and soon our focus of MEMS activity would be MEMS-based Bio-sensors. I am presently teaching a course on "Introduction to MEMS".

MEMS Activity at TIFR Bombay:

Our activity in MEMS began in 1996 when an Electron Beam Lithography (EBL) system was set-up on the JEOL Scanning Electron Microscope (SEM) in the SSE group. Using EBL, we can now make micron feature size photomasks or write sub-micron features directly on silicon wafer. Some of the microstructures we successfully tried first were,

1. Cantilevers : Cantilevers had 5-10 micron width and 50-100 micron length.

Many applications are

o        Acceleration sensors in automobiles (with inertial mass at the tip)

o        reed vibrators with resonant frequency - 300 Hz to 3 MHz

o        radiation detectors (using bending effects due to heating in bimetals)

o        optical micro-mirrors deflected by electrostatic fields

o        AFM or other near-field microscope tips

o        microprobes for biological probing


2. Cross beams : Crossbeam had 5-10 micron width and span of 100 microns.

             Two main applications are

o        as a thermally isolated platform at the center of the cross. This is useful in microcalorimetry

o        with a centrally attached mass it can be used as a 3-D accelerometer/ gyroscope in space applications.

3. Resonators : Resonators had a structure of double-suspension torsion resonator.

Dimensions were 5-10 micron widths in torsion arms, suspensions and 1-2 micron widths for the torsion wires. Very high Q ( in excess of 40,000) can be obtained by double suspension scheme.

 

Two main applications are

o        measure viscosity of gases/fluids in the resonant mode

o        vibration sensors in space vehicles and large antenna structures.


4. Spiral springs : Spiral springs have micro movements in perpendicular direction.

Main applications are

o        low stiffness spring

o        micro-movements to position an object attached to the center point

Continuing activity has led to several interesting structures like magnetic sensor using unbalanced resonator structure and curled tips. Papers have been presented at international conferences in Feb 1998. We plan to add new features to these devices to make them smart as well as useful to real users like space, defence etc.

 

Proceedings of International conferences :

Conference Papers on MEMS (1996-2005) :

    1. U.D. Vaishnav, P.R. Apte, S.G. Lokhre, V.R. Palkar and S.M. Pattalwar, "Micromechanical components with novel properties",

Proc. of SPIE, 3321, 287-297 (1996)
 

    1. S.G. Lokhre, K. Virwani, B. Gajanan, S.P. Pai, P.R. Apte, "Vibrational modes of MEMS resonators",

Proc. of SPIE, vol. 3903, Indo-Russian workshop on Micromechanical Systems, Delhi, Feb 2-4, 1999, pp 32-41
 

    1. P.R. Apte, "TRIZ in MEMS"

Proc. of SPIE, vol. 3903, Indo-Russian workshop on Micromechanical Systems, Delhi, Feb 2-4, 1999, pp 42-47
 

    1. P.R. Apte, S.G. Lokhre, S.C. Purandare, B. Gajanan, K. Virwani, "Current-controlled curled tip",

Proc. of SPIE, vol. 3903, Indo-Russian workshop on Micromechanical Systems, SPL, Delhi, Feb 2-4, 1999, pp 223-231
 

    1. A.D. Shaligram, P.R. Apte, D.C. Gharpure, L. Sudha, "Design of a hybrid silicon fiber optic sensor array for tactile sensing",

Proc. of SPIE, vol. 3903, Indo-Russian workshop on Micromechanical Systems, Feb 2-4, 1999, pp 216-222

    1. S.G. Lokhre, P.R. Apte, R.Raajeev and R. Lal, "Micro-resonator modified as magnetic sensor"

SPIE's 2000 symposium on "micromachining and microfbrication", Santa Clara, CA, USA on Sept. 18-21, 2000

    1. P.R. Apte, “VLSI Technology and MEMS”,

National Seminar on VLSI: System, Design and Technology, IIT Bombay, 9-11 Dec 2000

    1. P. R. Apte, “2-D Simulation of Laminating Stresses and Strains in MEMS Structures”

ICMAT 2003 held at Singapore (July 2001)

 

    1. R. P. Dhote, S. S. Chiluveru, S. A. Chandorkar and P. R. Apte, “A Novel Heatuator”

 

ICMAT 2003 held at Singapore (Dec 2003)

 

    1. N. N. Naik, A. A. Ghangrekar, S. U. Kalghatgi, S. S. Shetty and P. R. Apte, “Electrical and Heat flow Simulation of MEMS Structures Using SPICE”,

 

ICMAT 2003 held at Singapore (Dec 2003)

 

    1. P. R. Apte,  L. K.  Mohanta and A. C. Vartak, “Micro-miniaturized Electrophoresis DNA Separator using MEMS”,

 

SPIE conf Photonics West 2005, San Jose, 22-27 Jan 2005

 

    1. P. R. Apte, A.  Gawarikar+, G. Ajishna and S. K. Sahoo “A Novel High-Q Torsion Microresonator ”,

 

SPIE conf Photonics West 2005, San Jose, 22-27 Jan 2005


 
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