Force and Interaction of colloidal particle under temperature gradients
Date Issued
2015
Date
2015
Author(s)
Tseng, Tzu-Wei
Abstract
In the presence of a thermal gradient, the motion of colloidal particles drift along a temperature gradient is known as thermophoresis. There is no clear theory so far to explain the phenomenon of thermophoresis because of the complicated interaction between particles and solvents. Therefore there are many transport mechanisms of thermophoresis which depend on different conditions are reported. One of the mechanisms of particle thermophoresis is caused by slip flow which is about the moving ions inside electric double layer. Slip flow was observed others studies, but it hasn’t been directly measured until now. Besides most of the researches study the effects of thermophoresis by measuring Soret coefficient and thermal diffusion coefficient, however thermophoretic force of colloidal particle is rarely discussed. In our experiment, we set an optical tweezers system to measure force of colloidal particle under temperature gradients in different conditions. In addition we studied the interaction of two colloidal particles by measuring force. We found the force of colloidal particle is linearly dependent to temperature gradients and particle size. On the studies of two colloidal particle interactions, we found that when two particles get close enough, force of two particles along the temperature gradient become smaller. Moreover we observed the motion of slip flow around the particle by trajectories of tracers. By measuring the changes in velocity of tracer particles we could verify the results of interaction of two colloidal particles.
Subjects
Colloidal particle
thermophoresis
Slip flow
Type
thesis