Ultrathin crystalline silicon–based omnidirectional strain gauges for implantable/wearable characterization of soft tissue biomechanics

Monitoring soft-tissue biomechanics is of interest in biomedical research and clinical treatment of diseases. An important focus is biointegrated strain gauges that track time-dependent mechanics of targeted tissues with deforming surfaces over multidirections. Existing methods provide limited gauge factors, tailored for sensing within specific directions under quasi-static conditions. We present development and applicability of implantable/wearable strain gauges that integrate multiple ultrathin monocrystalline silicon-based sensors aligned with different directions, in stretchable formats for dynamically monitoring direction angle-sensitive strain. We experimentally and computationally establish operational principles, with theoretical systems that enable determination of intensities and direction of applied strains at an omnidirectional scale. Wearable evaluations range from cardiac pulse to intraocular pressure monitoring of eyeballs. The device can evaluate cardiac disorders of myocardial infarction and hypoxia of living rats and locate the pathological orientation associated with infarction, in designs with possibilities as biodegradable implants for stable operation. These findings create clinical significance of the devices for monitoring complex dynamic biomechanics.