Thermally activated state transition technique for femto-Newton-level force measurement

Abstract

We develop and test a thermally activated state transition technique for ultraweak force measurement. As a force sensor, the technique was demonstrated on a classical Brownian bead immersed in water and restrained by a bistable optical trap. A femto-Newton-level flow force imposed on this sensor was measured by monitoring changes in the transition rates of the bead hopping between two energy states. The treatment of thermal disturbances as a requirement instead of a limiting factor is the major feature of the technique, and provides a new strategy by which to measure other ultraweak forces beyond the thermal noise limit.

Rich stochastic dynamics of co-doped Er:Yb fluorescence upconversion nanoparticles in the presence of thermal, non-conservative, harmonic and optical forces

“…Moreover, external forces comparable to thermal forces can be included, thereby adding experimental parameters that further enrich stochastic dynamics far from equilibrium. For example, optical trapping has long been used to accelerate and bind particles with laser light and study basic thermodynamic [10,11] and chemical and hydrodynamic [12,13] processes in the presence of optical forces.…”