Microelectromechanical device for lateral force calibration in the atomic force microscope: Lateral electrical nanobalance

Abstract

Calibration of lateral force microscopy cantilevers is essential for the measurement of nanonewton and piconewton frictional forces, which are critical to analytical applications of polymer surfaces, biological structures, and organic molecules at nanoscale lateral resolution. We have developed a compact and easy-to-use reference artifact for this calibration, the lateral electrical nanobalance (LEN), which can be made traceable to the Système International d'Unités. A noncontact method has been developed for measuring the lateral spring constant of these artefacts, by a combination of electrical measurements and Doppler velocimetry. Traceability is crucial to ensure that force measurements by an atomic force microscope are comparable to those made by optical tweezers and other methods. The LEN is a microelectromechanical system device fabricated by silicon-on-insulator micromachining, and therefore has extremely low mass and good immunity to vibration.