Stanford engineers have invented a wireless pressure sensor that has already been used to measure brain pressure in lab mice with brain injuries. The underlying technology has such broad potential that it could one day be used to create skin-like materials that can sense pressure, leading to prosthetic devices with the electronic equivalent of a sense of touch.

A nine-member research team led by Chemical Engineering Professor Zhenan Bao detailed two medical applications of this technology in Nature Communications.

In one simple demonstration they used this wireless pressure sensor to read a team member's pulse without touching him.

In a more complex application, they used this wireless device to monitor the pressure inside the skull of a lab mouse, an achievement that could one day lead to better ways to treat human brain injuries.

Bao's wireless sensor is made by placing a thin layer of specially designed rubber between two strips of copper. The copper strips act like radio antennas. The rubber serves as an insulator.

The technology involves beaming radio waves through this simple antenna-and-rubber sandwich. When the device comes under pressure, the copper antennas squeeze the rubber insulator and move infinitesimally closer together.

That tiny change in proximity alters the electrical characteristics of the device. Radio waves passing through the two antennas slow down in terms of frequency. When pressure is relaxed, the copper antennas move apart and the radio waves accelerate in frequency.

The engineers proved that this effect was measurable, giving them a way to gauge the pressure exerted on the device by tracking the frequency of radio waves passing through the device.