Piezoresistive cantilevers for nanomechanical sensing

Microfabricated cantilevers have enabled a wide range of applications in scanning probe microscopies (SPM) and in high-sensitivity nanomechanical sensors. The use of piezoresistivity for self-sensing the cantilever motion is preferred to the standard optical readout for some applications, in view of the advantages that it offers in terms of miniaturization, operation in non-transparent liquid media and capability of simultaneously addressing arrays of devices. Although in principle piezoresistive cantilevers should have a lower resolution than their optical counterparts, current devices can achieve similar performances. This is because a large amount of work has been devoted in the past two decades to their development. This paper provides a short review of the field of piezoresistive cantilevers. We discuss the device performances for the measurement of forces or surface stresses in static operation, or masses in dynamic operation. We then describe the fabrication technologies and materials that are typically used to manufacture the cantilevers. Finally, the main applications in the domains of SPM and nanomechanical sensing are presented.