Parylene-Based Strain Sensors for Bone

This paper presents a novel flexible implantable device to provide high-resolution mechanical strain data from a bone surface in real time. The design of the device has been verified with finite-element analysis, and a prototype has been successfully fabricated which consists of a thin-film metal gauge encapsulated between two layers of parylene-C. The prototype has been characterized simultaneously with a commercial strain gauge using tensile testing. The results indicated that the strain sensitivities of the prototype were approximately 2.5 times greater than those of commercial gauges. In addition, real-time strain data collection has been successfully demonstrated on bone surfaces with the novel devices using mechanical testing of chicken tibiae in three-point bending.