"Towards a dynamic control of spurious forces with optical tweezers"

Towards a dynamic control of spurious forces
with optical tweezers

Juan Pablo Staforelli
Center for Optics and Photonics, Universidad de Concepción
Casilla 160-C, Concepción, Chile

A spatial diffusion gradient appears in situations where the diffusion coefficient of a colloidal
object becomes position dependent, which causes a spurious drift- a shift of the position
distribution mean. In this work, the stochastic nature that account in this phenomena is studied
preliminarily in a system of two polystyrene micro-spheres in an optical tweezers set-up. Here,
the spurious drift, and the related, spurious forces account for an asymmetry in the particle
position distribution which is modulated via spatial control of the initial particle distribution.
Experimental data gives the diffusion term, the drift of the mean position, the propagator shape
and some fundamental stochastic parameters of the system. Additionally, it is a challenge to
perform a real-time spatial control by setting diffusion gradients through dynamic wall geometries.
This would allow one to observe the brownian particle transport through a channel whose walls -
multiple trapped particles- are modulated in real-time. To perform this, a real-time feedback
control mechanism with holographic optical traps is engineered to adjust the position of the
channel in response to information of the particle drift from its initial position. This work aims
to study the behavior of the drift term in the interaction between few particles, particle-wall and
particle-potential, as well to get new insight in natural scenarios concerning diffusive process as
those found in cell membrane biology.

Date: July 17, 2013 (Wednesday)
Time: 15:40-16:40
Place: SA240