We show that trapping and manipulation of microparticles can be achieved by Rayleigh convection currents using a low power lasers. Light absorbed by thin film of amorphous silicon (a:Si) creates the convection currents. In contrast to previous works, we show that multiple trapping can be achieved using solid microparticles without the creation of vapor bubbles. For low power (~1 mW), particles are trapped at the center of the beam, however at higher powers (~3 mW) particles are trapped on a ring around the beam due to two competing forces: Stokes and thermophoretic forces. Numerical simulations confirm that thermal gradients are responsible for the trapping mechanism.

Date Published: 16 September 2014
PDF: 5 pages
Proc. SPIE 9164, Optical Trapping and Optical Micromanipulation XI, 91643C (16 September 2014); doi: 10.1117/12.2061266

Published in SPIE Proceedings Vol. 9164:
Optical Trapping and Optical Micromanipulation XI
Kishan Dholakia; Gabriel C. Spalding, Editor(s)