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Brownian Motion in Viscoelastic Confinement

English title Brownian Motion in Viscoelastic Confinement
Applicant Jeney Sylvia
Number 126945
Funding scheme Project funding
Research institution Laboratoire de nanostructures et nouveaux matériaux électroniques EPFL - SB - IPMC - LNNME
Institution of higher education EPF Lausanne - EPFL
Main discipline Other disciplines of Physics
Start/End 01.10.2009 - 30.09.2010
Approved amount 61'440.00
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All Disciplines (5)

Discipline
Other disciplines of Physics
Fluid Dynamics
Theoretical Physics
Material Sciences
Biophysics

Keywords (8)

photonic force microscopy; optical tweezers; hydrodynamic interactions; viscoelasticity; single particle tracking; hydrodynamic memory effect; viscoelastic interactions; confined diffusion

Lay Summary (English)

Lead
Lay summary
Diffusion governed by Brownian motion is an efficient transport mechanism on short time and length scales. Even a highly organized system like a living cell relies in many cases on the random Brownian motion of its constituents to fulfill complex functions. A Brownian particle will rapidly explore a heterogeneous environment that in turn strongly alters its trajectory. Thus, detailed information about the environment can be gained by analyzing the particle's trajectory. Precise characterization of local diffusion effects in constraining configurations, as present in an intra- or extra- cellular environment or more simply in an optical trap, microfluidic channels, on micropatterned surfaces has become more accessible with the development of high resolution observation and manipulation tools. Investigations of the properties of a colloidal probe in such confining structures should provide fundamental insights in physical, chemical and biological processes such as viscoelastic interactions, particle transport through porous media, molecular diffusion on and through cell membranes and so on. Recently, we used Optical Trapping Interferometry (OTI) based on optical trapping and interferometric particle detection, to study at very short time (1?s) and length (1nm) scales the Brownian motion of a model system consisting of a single micrometer-sized sphere immersed in a viscous fluid like water. We could resolve the "hydrodynamic memory effects" arising from the fluid's inertia and acting on the sphere, changing its diffusion constant at short times. Our experiments confirmed existing theoretical predictions of this phenomenon largely ignored in typical optical trapping experiments, as well as in experimental biophysics in general.In order to pursue the study of such confining effects, we would like to track, our Brownian probe when it is embedded in a polymer network. Thereby, we will need to develop adequate theories to be able to calibrate and interpret our data. For example, we expect that the high-frequency response of a viscoelastic polymer solution gives information on the nanomechanical properties of the constituting polymeric chains. In particular, highly dynamic polymers, like the ones encountered in a living cell, should transmit their mechanical and dynamical signatures to the Brownian particle. After establishing a new data analysis strategy to simple viscoelastic model fluids, like a Maxwell fluid, we will apply it to more complex solutions, like a polymer bulk. The main goal of this project is to validate the use of a Brownian particle to study viscoelastic properties of biological samples with unprecedented bandwidth.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Associated projects

Number Title Start Funding scheme
121396 Multidimensional Optical Force NanoSpectroscope 01.06.2009 R'EQUIP
113529 Brownian Motion in confined geometries 01.10.2006 Project funding

Abstract

Diffusion governed by Brownian motion is an efficient transport mechanism on short time and length scales. Even a highly organized system like a living cell relies in many cases on the random Brownian motion of its constituents to fulfill complex functions. A Brownian particle will rapidly explore a heterogeneous environment that in turn strongly alters its trajectory. Thus, detailed information about the environment can be gained by analyzing the particle’s trajectory. Precise characterization of local diffusion effects in constraining configurations, as present in an intra- or extra- cellular environment or more simply in an optical trap, microfluidic channels, on micropatterned surfaces has become more accessible with the development of high resolution observation and manipulation tools. Investigations of the properties of a colloidal probe in such confining structures should provide fundamental insights in physical, chemical and biological processes such as viscoelastic interactions, particle transport through porous media, molecular diffusion on and through cell membranes and so on. Recently, we used Optical Trapping Interferometry (OTI) based on optical trapping and interferometric particle detection, to study at very short time (1µs) and length (1nm) scales the Brownian motion of a model system consisting of a single micrometer-sized sphere immersed in a viscous fluid like water. We could resolve the “hydrodynamic memory effects” arising from the fluid’s inertia and acting on the sphere, changing its diffusion constant at short times. Our experiments confirmed existing theoretical predictions of this phenomenon largely ignored in typical optical trapping experiments, as well as in experimental biophysics in general.In the past 2,5 years, within the frame of the on-going SNF project (N° 113529, “Brownian Motion in confined geometries”), we characterized in detail the short-time dynamics of a Brownian particle next to a rigid wall. Our experimental data could be fitted by a very recently developed theory. In order to pursue the study of such confining effects, we would like to track, down to very short time scales, our Brownian probe when it is embedded in a polymer network. Thereby, we will need to develop adequate theories to be able to calibrate and interpret our data. For example, we expect that the high-frequency response of a viscoelastic polymer solution gives information on the nanomechanical properties of the constituting polymeric chains. In particular, highly dynamic polymers, like the ones encountered in a living cell, should transmit their mechanical and dynamical signatures to the Brownian particle. After establishing a new data analysis strategy to simple viscoelastic model fluids, like a Maxwell fluid, we will apply it to more complex solutions, like a polymer bulk or a network composed of protein fibrils, involved in human neurodegenerative diseases. The main goal of this project is to validate the use of a Brownian particle to study viscoelastic properties of biological samples with unprecedented bandwidth.
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