Stretchable sensor can measure body movements

The self contained large area wireless strain sensor, which operates at around 1.5GHz, is based on the concept of multi layer microfluidic stretchable radiofrequency electronics (µFSRFEs). It has been designed to measure intensive body movements and wirelessly send information directly to a computer. Compared to existing solutions, the integrated strain sensor is capable of remotely detecting repeated high tensile dynamic strains of up to 15% over very large surfaces or movable parts. According to lead researcher Zhigang Wu, it is also able to remove all hardwiring to external storage or data processing equipment. "Unlike conventional electronic devices, the major part of the sensor is a mechanically reconfigurable and reversibly deformable patch antenna," said Wu. "This consists of two layers of liquid metal alloy filled microfluidic channels in a silicone elastomer." To create the sensor, a simplified rf transmitter composed of miniaturised rigid active ICs associated with discrete passive components was assembled on a flexible pcb and then heterogeneously integrated to the antenna. According to Wu, the elastic patch antenna could withstand repeated mechanical stretches whilst still maintaining its electrical function. It was also able to return to its original state after removal of the stress. "Not only did the antenna act as a radiator for transmitting and receiving rf signals like any other conventional antenna, it also acted as a reversible large area strain sensor in the integrated device." In the real life demonstration, the integrated strain sensor successfully monitored periodically repeated human body motion and wirelessly transmitted the measured data to the custom designed receiver at a distance of 5m. Wu believes the technology will pave the way for a myriad of new applications.