MEMS passive strain recorders/counters

The goal of this proposal is to develop small 2 MEMS peak strain recorders and strain cycle counters. A user can adhere the MEMS device to a structure, and come back a week or a year later, and take a photograph that records the peak strain and number of cycles experienced by the structure. This is a passive, purely micro-mechanical system.

Most strain gages are resistance based: they are small (

Typically strain values are small (1 micro strain = 1 ppm); for a gage length of 1 cm, measuring 10 micro strain would require detecting 0.1 micron changes. Measuring such small changes is possible using a passive MEMS system, no power source required. A MEMS latching system is used to permanently store peak strain values. The MEMS device contains the micro-scale equivalent of a bar code and the recorded strain can be read optically using a smartphone. Modern smartphone cameras can in fact measure at the micro-scale. The key to this is Fourier based techniques that can robustly detect sub-micron scale displacements.

Small, inexpensive and passive recording gages open up an entirely new possibility: the ubiquitous monitoring of mechanical structures. Just as many consumer goods come with disposable passive RFID tags, many mechanical components could be tagged with a MEMS strain recording patch. Aircraft components, automobile parts, wind turbines, artificial limbs, buildings, any mechanical part could have a MEMS patch applied and then be monitored to measure peak loads. Has the structure been overloaded? Has this structure exceed its safe limit? Key to this potential is making the strain recorders small and passive using MEMS.