The hands and fingers can be thought of as diagnostic windows into different aspects of our human physiology. Hand activity and grip strength may be useful indicators of person’s overall health.

Researchers at Harvard’s School of Engineering have developed safe and accurate force and strain sensors that can be attached directly to fingers for  monitoring. The devices can work continuously for extended periods of time, measuring the force and strain values with almost no lag time.

This is an impressive achievement, as similar previously developed devices were slow to respond and their output didn’t change linearly in proportion to the forces felt. Moreover, the conductive liquid that was often relied upon wasn’t exactly safe if it managed to escape.

The new device relies on silicone-based force and strain sensors that use a solution of potassium iodide and glycerol, which is non-toxic to the human body. The sensors have a layered structure of tiny cylinders within which the liquid is pushed through as forces are applied to the device. Because of the narrow nature of the cylinders and the fact that there are many of them, the overall device is able to achieve highly accurate, near real-time measurements.