Receptor-free nanomechanical sensors

Nanomechanical response of molecular adsorption has been demonstrated as the basis for a number of extremely sensitive sensors. Molecular adsorption on microcantilevers results in nanomechanical motion due to adsorption-induced surface stress variation. Chemical selectivity in nanomechanical sensors is achieved by immobilizing receptors on the cantilever surface. Although receptor-based detection has high selectivity for biomolecular detection, it fails when applied to small molecule detection. Nanomechanics, however, offer new possibilities for achieving chemical selectivity that do not use any receptors. For example, small thermal mass or high temperature sensitivity of a cantilever beam could be used for detecting molecular adsorption using photothermal effects and physical property variation due to temperature. Here we describe two such techniques for achieving chemical selectivity without using any receptor molecules.