Design of microfabricated strain gauge array to monitor bone deformation in vitro and in vivo

We present the design of a strain gauge embedded in polydimethylsiloxane (PDMS) that could be implanted and used for monitoring strain on surfaces of bones with high resolution. Our ultimate goal is to design and fabricate the device such that it could be used to provide real-time data of strain development in live subject. We have simulated the mechanical characteristics of thin-film metal strain gauges embedded in a flexible substrate made from polydimethyl-siloxane (PDMS) with various loading conditions using ANSYS® finite element analysis tool. Various gauge designs were subjected to stresses from several different directions. Linear relationships between fractional change of resistance and nominal resistance were found for both tensile and compressive stress applied on the gauges. Most significantly, the simulation demonstrated that external stresses were effectively transmitted through the PDMS layer to the thin-film metal, validating our approach.