Giant piezoresistance

A new experiment, conducted by scientists from France, Switzerland, and the UK, has recorded the largest-ever change brought about in a bulk material’s electrical resistance by straining the material at room temperature. Called piezoresistance, the phenomenon is often exploited in sensors. In simple metal-foil piezoresistors, the kind used to examine the integrity of a concrete wall or to monitor a prosthetic limb, the change in resistance per unit of strain (a ratio referred to as the gage factor) has a typical value of about 2. For silicon-based piezoresistors, the kind used in cell phones and airbag accelerometers, the gage factor is usually about 100. The new experiment uses a silicon–aluminum hybrid material in which the arrangement of the components, not their composition, is of paramount importance. The metal—in this case aluminum—is effectively a current shunt; applying a mechanical stress to the device deflects current toward or away from the shunt...