Thermally induced micro-motion by inflection in optical potential

Martin Šiler,Artem Ryabov,Petr Jákl,Radim Filip,Oto Brzobohatý,Pavel Zemánek

doi:10.1038/s41598-017-01848-4

Abstract

ABSTRACTRecent technological progress in a precise control of optically trapped objects allows much broader ventures to unexplored territory of thermal motion in non-linear potentials. In this work, we exploit an experimental set-up of holographic optical tweezers to experimentally investigate Brownian motion of a micro-particle near the inflection point of the cubic optical potential. We present two complementary views on the non-linear Brownian motion. On an ensemble of stochastic trajectories, we simultaneously determine (i) the detailed short-time position statistics and (ii) the long-distance first-passage time statistics. We evaluate specific statistical moment ratios demonstrating strongly non-linear stochastic dynamics. This is a crucial step towards a possible massive exploitation of the broad class of complex non-linear stochastic effects with objects of more complex structure and shape including living ones.

Highlights

Biological molecular machines utilize non-linearity and asymmetry of their free-energy landscapes to produce a useful directed motion in violently fluctuating biological environments[1, 2]
The first in a line already yields a stochastic dynamics with a onfunmonb-elrinoefarinptortiegnutiinalgs,pthroepsetrrotinegs.cuItbiicndpuotceenstitahleVo(xv)er∼-dμam3xp3/e3d, non-linear motion, for which both the position x and the first-passage time τ depends on the temperature T of the environment in a universal, but different way
Without thermal noise (T = 0, deterministic motion), the over-damped particle is unable to pass through the inflection point at x = 0 and remains there as the dashed deterministic trajectory in Fig. 1 illustrates

Summary

Introduction

Biological molecular machines (or Brownian motors) utilize non-linearity and asymmetry of their free-energy landscapes to produce a useful directed motion in violently fluctuating biological environments[1, 2]. In the present work, we report for the first time an experimental observation of the conversion of the thermal noise to a directed motion dictated by a specific type of the non-linearity with an inflection point We believe that such conversion of stochastic behaviour to a local motion can be advantageously exploited to develop new thermal ratchets and advanced thermal motors. In a complementary way, (ii) by a global, large-distance first-passage time statistics[19], which is crucial for understanding e.g. rates of chemical processes[20], phase transitions and passages through bifurcations[21, 22], and macroscopic transport properties of complex systems[23,24,25] Both these approaches provide complementary pictures of the non-linear Brownian motion and in particular, they allow to understand beneficial global and local effects of thermal noise on the stochastic dynamics[26].

Methods

Results

Conclusion