2020/06/29 by Lars S. Madsen, Muhammad Waleed, Catxere A. Casacio +4
Physics and Astronomy · #Dissipation #Mechanical and Optical Resonators #Micro and Nano Robotics #Optical tweezers #Orbital Angular Momentum in Optics #Particle (ecology) #Ranging #Thermal #Thermal fluctuations #Tracking (education) #Ultrashort pulse #Viscosity #cond-mat.soft #physics.bio-ph #physics.ins-det #physics.optics #quant-ph
paper · pdf · doi:10.1038/s41566-021-00798-8
arxiv created 2020/06/29 · openalex created_date 2020/07/16 · openalex publication_date 2021/04/22 · arxiv updated 2021/05/26 · openalex updated_date 2026/08/05
Viscosity is an important property of out-of-equilibrium systems such as active biological materials and driven non-Newtonian fluids, and for fields ranging from biomaterials to geology, energy technologies and medicine. However, noninvasive viscosity measurements typically require integration times of seconds. Here we demonstrate a four orders-of-magnitude improvement in speed, down to twenty microseconds, with uncertainty dominated by fundamental thermal noise for the first time. We achieve this using the instantaneous velocity of a trapped particle in an optical tweezer. To resolve the instantaneous velocity we develop a structured-light detection system that allows particle tracking with megahertz bandwidths. Our results translate viscosity from a static averaged property, to one that may be dynamically tracked on the timescales of active dynamics. This opens a pathway to new discoveries in out-of-equilibrium systems, from the fast dynamics of phase transitions, to energy dissipation in motor molecule stepping, to violations of fluctuation laws of equilibrium thermodynamics.