If you're interested in measuring the strain on the surface of a part, in the
same way as you would with a strain gage, then the only MEMS device that I'm
aware of is the BiAST (BiAxial Strain Transducer) being developed by Sarcos
(http://www.sarcos.com/memsspec_uast.html).

It is actually better described as a micro-extensometer rather than a strain
gage, but with a gage length of around 10 millimeters, its output should be
similar to that of a small strain gage. The most interesting features are:

* practical resolution of the order of 1 microstrain.
* onboard A/D conversion, so that the sensor actually communicates digitally
with the data acquisition system with the obvious consequences for noise.
* potentially reusable, as the MEMS device package is attached by something like
screws to the stems of 3 mounting pads which are bonded to the surface whose
strain is to be measured. This is important because initially, at least, these
sensors will be considerably more expensive than normal strain gages.

These devices will hopefully become available in the next few months. If you'd
like some more information, I can forward a couple of papers in PDF format.

There are of course non-MEMS alternatives to electrical strain gages based on
fibre optics.

If you learn of any other MEMS-based strain measurement devices, please let us
know.

-- Emilio

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Dr Emilio P. Calius
Research Engineer: Smart Materials and Structures
Industrial Research Limited
PO Box 2225, Auckland, New Zealand
Ph: +64 9 303 4116,     Fax: +64 9 307 0618