Simple optical characterisation for biomimetic micromachined silicon strain-sensing structure

Simple optical characterisation for biomimetic micromachined silicon strain-sensing structure

Wicaksono, D.H.B.
Pandraud, G.
French, P.J.

Electrical Engineering, Mathematics and Computer Science

Department of Microelectronics

2005-09-08

This paper presents an on-going work to develop micromachined silicon-based strain sensor inspired from the campaniform sensillum of insects. We present simple optical setup for the characterisation of a membrane-in-recess structure as an early stage in mimicking the natural sensor. The microstructure is a 500 nm-thick SiO2/SiN circular membrane, burried 13 ?m from the surface of a 3x3 mm, 525 ?m thick Si-chip. The chip was attached to a 45x10x0.525 mm Si beam. The simple optical characterisation setup is based on imaging the reflected laser beam from the biomimetic structure. Since an optical cavity between the membrane and the Si beams beneath was formed, ideal flat-parallel Fabry-Perot interferometer equation was applied to interpret the results semi-quantitatively. We obtained 2-D interference fringe pattern having 3 orders of maxima from the middle to the edge of the circular apperture, as a result of an initial internal membrane stress. The pattern changed non-linearly as we applied flexural strain from behind the beam up to 50 ?m, most probably caused by nonlinear deflection of the membrane (i.e. the membrane did not deflect similarly as the beam beneath it). This phenomena might explain one of the strain-amplifying properties of this biomimetic strain sensing microstructure.

biomimetrics
strain sensing
MEMS
optical characterisation
Fabry-Perot interferometer

http://resolver.tudelft.nl/uuid:5d8ed60f-5936-4fac-8b34-3ca42355834e

SPIE

0277-786X

Proceedings of SPIE, 2005 vol. 5872

Institutional Repository

conference paper

(c)2005 Wicaksono, D.H.B., Pandraud, G., French, P.J.