Wireless electronic ‘stickers’ developed to gauge forces between objects

Developed at the University of California San Diego, the so-called ForceSticker consists of a capacitor that is just a few millimetres thick, and a radiofrequency identification (RFID) sticker.

The capacitor is made of a soft polymer sheet sandwiched between two conductive copper strips. When an external force is applied, the polymer compresses, drawing the copper strips closer together, thereby increasing the electric charge in the capacitor.

An RFID tag is then temporarily powered up by a radio signal emitted from a handheld RFID reader. That tag utilises an integrated antenna to relay a modified version of the signal back to the reader, with information on the capacitor's charge level. Custom software then converts that data into a measurement of applied force.

The force stickers run without batteries and fit in tight spaces that make them versatile for applications that include giving robots a sense of touch, improving biomedical devices, monitoring the safety of industrial equipment, and improving the accuracy and efficiency of inventory management in warehouses.