CPM Seminar

Nanomechanical Systems:
Toward single-molecule and single-quantum measurements

Michael Roukes

Kavli Nanoscience Institute
California Institute of Technology

Advanced techniques in nanoscience now enable the creation and measurement of ultrasmall mechanical devices. These nanoelectromechanical systems (NEMS) offer unprecedented opportunities for sensing and quantum measurements. I will describe several specific applications of NEMS that we are currently pursuing: vacuum-based force sensing, single-molecule mass spectrometry, fluid-based biochemical force assays for single-molecule molecular recognition, and number-state measurements of single quantum jumps in a NEMS device at ultralow temperatures.

The first two applications employ ultraminiature mechanical devices that offer sensitivity down to the single-molecule limit. Their reduced size yields extremely high fundamental vibrational frequencies while simultaneously preserving very high mechanical responsivity. For vacuum-based applications, this powerful combination of attributes translates directly in to high force and mass sensitivity — in the near future we should attain the zeptonewton force regime and single Dalton (1 amu) mass levels, respectively. In fluidic media, even though the high quality factors attainable in vacuum become precipitously damped, the small device size and high compliance still yields response below the piconewton level (roughly the force required to break individual hydrogen bonds within a macromolecule). Finally, single-quantum experiments involve ultrasensitive measurements on high frequency devices while avoiding a linear coupling. This represents a novel class of measurements anticipated years ago, but not yet realized with mechanical systems.