The ability to monitor, in real time, the mechanical forces on tendons after surgical repair could allow personalized rehabilitation programmes to be developed for recovering patients. However, the development of devices capable of such measurements has been hindered by the strict requirements of biocompatible materials and the need for sensors with satisfactory performance. Here we report an implantable pressure and strain sensor made entirely of biodegradable materials. The sensor is designed to degrade after its useful lifetime, eliminating the need for a second surgery to remove the device. It can measure strain and pressure independently using two vertically isolated sensors capable of discriminating strain as small as 0.4% and the pressure exerted by a grain of salt (12 Pa), without them interfering with one another. The device has minimal hysteresis, a response time in the millisecond range, and an excellent cycling stability for strain and pressure sensing, respectively. We have incorporated a biodegradable elastomer optimized to improve the strain cycling performances by 54%. An in vivo study shows that the sensor exhibits excellent biocompatibility and function in a rat model, illustrating the potential applicability of the device to the real-time monitoring of tendon healing.
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C.M.B. acknowledges postdoctoral fellowship support from the Swiss National Science Foundation (Postdoc Mobility Fellowship no. P2EZP2_152118) and the European Commission (Marie-Curie International Outgoing Fellowship grant no. 622362). Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award ECCS-1542152. B.C.S. acknowledges the National Research Fund of Luxembourg for financial support (project no. 6932623).
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Nature Biomedical Engineering (2019)
Microsystems & Nanoengineering (2019)
Nature Electronics (2018)
Nature Electronics (2018)