More Sensitive Piezoresistive Sensors

Metal-semiconductor composites exhibit a piezoresistive effect at room temperature that is 10 times greater than that of pure metals or semiconductors, according to a study by Alistair C. H. Rowe of Ecole Polytechnique, Palaiseau, France, and coworkers (Phys. Rev. Lett. 2008, 100, 145501). The discovery may lead to the development of new types of sensors for microelectromechanical systems (MEMS) and data storage devices. Piezoresistance is one example of a group of phenomena in which applying a weak force, in this case mechanical stretching, to a material can lead to a great enough change in electrical resistance to form the basis of sensing technologies. Simple piezoresistive sensors used to monitor the integrity of concrete walls and prosthetic limbs, for example, are made from metal foils. Versions made from silicon are 50 times more sensitive and are used in the MEMS-based triggers of automobile air bags. Now, by combining micrometer-thick films of aluminum and silicon, Rowe's team has formed composite sensors that are the most sensitive room-temperature piezoresistance sensors to date.