Implantable sensors with a disappearing act

An implantable strain and pressure sensor designed to naturally decompose after its useful lifetime is reported in an animal study published online this week in Nature Electronics. The device could be used to monitor the stresses on damaged soft tissue in real time, and help design personalized rehabilitation programs for recovering patients.

Degradable sensors are an emerging technology in which devices are designed to naturally decompose after a pre-defined duration, eliminating the need for a second surgery to extract the device. However, existing devices tend to have limited sensing performance or unproven biocompatibility.

Paige Fox, Zhenan Bao, and colleagues report a stretchable and biodegradable strain and pressure sensor composed of fully biocompatible materials. The implantable sensor is sensitive enough to discriminate strains as small as 0.4% and pressures as small as 12 Pa (the pressure exerted by a grain of salt). The authors tested the biocompatibility of their devices by implanting the sensors in the back of a rat. No adverse inflammatory reaction was observed after eight weeks of implantation (except for an initial inflammatory reaction in the first week).

The researchers were also able to control the decomposition of the device so that its lifetime was compatible with the time required for tissue healing. Moreover, the sensor was engineered such that it would operate without a noticeable reduction in sensitivity during the decomposition process.