In suspensions containing microspheres and a sub-micron species, such as nanoparticles or a polymer, an attractive force can result between the microspheres. This attraction arises due to an entropic interaction, often referred to as a depletion force. In this work we demonstrate an application of the depletion force to the controlled assembly of crystalline templates for the production of photonic band gap (PBG) materials. The method makes use of holographic optical tweezers to assemble crystalline arrays of silica or polystyrene microspheres, in which depletion interactions are used to stabilise the structures being built. In addition, we use the holographic optical tweezers to characterise the attraction between pairs of microspheres in the system.

Date Published: 29 August 2008
PDF: 9 pages
Proc. SPIE 7038, Optical Trapping and Optical Micromanipulation V, 70380K (29 August 2008); doi: 10.1117/12.795070

Published in SPIE Proceedings Vol. 7038:
Optical Trapping and Optical Micromanipulation V
Kishan Dholakia; Gabriel C. Spalding, Editor(s)