The Color of Brownian Motion
Event details
| Date | 14.06.2013 |
| Hour | 14:15 |
| Speaker | Dr. Sylvia Jeney, Laboratoire de Physique de la Matière Complexe - LPMC, EPFL |
| Location | |
| Category | Conferences - Seminars |
Observation of the Brownian motion of a small probe interacting with its environment is one of the main strategies to characterize soft matter. Initially, the particle is driven by rapid collisions with the surrounding solvent molecules, referred to as thermal noise. Later, the friction between the particle and the viscous solvent damps its motion. Conventionally, thermal force is taken to be characterized by a Gaussian white noise spectrum. The friction is assumed to be given by the Stokes drag, suggesting that motion is overdamped at long times, when inertia becomes negligible.
Recently, we measured the noise spectrum of the thermal forces by tracking with high resolution a single micron-sized sphere suspended in a fluid, and confined by a stiff optical trap. Coupling between sphere and fluid gives rise to hydrodynamic memory and a resonance, equivalent to a colored peak in the power spectral density of the sphere’s thermal fluctuations. Our results reveal that motion is not overdamped, and the particle-fluid-trap system can be considered a nanomechanical resonator. By bridging novel theoretical insights to model experiments with unprecedented accuracy, we are aiming at developing a novel type of multidimensional, time-resolved, near-field sensor for the study and manipulation of soft and living matter.
Recently, we measured the noise spectrum of the thermal forces by tracking with high resolution a single micron-sized sphere suspended in a fluid, and confined by a stiff optical trap. Coupling between sphere and fluid gives rise to hydrodynamic memory and a resonance, equivalent to a colored peak in the power spectral density of the sphere’s thermal fluctuations. Our results reveal that motion is not overdamped, and the particle-fluid-trap system can be considered a nanomechanical resonator. By bridging novel theoretical insights to model experiments with unprecedented accuracy, we are aiming at developing a novel type of multidimensional, time-resolved, near-field sensor for the study and manipulation of soft and living matter.
Practical information
- Informed public
- Free
Organizer
- ICMP (Arnaud Magrez, Raphaël Butté and Woflgang Harbich)
Contact
- Sylvia Jeney