Speed enhancement of multi-particle chain in a traveling standing wave

A moving array of optical traps created by interference of two counter-propagating evanescent waves has been used for delivery of particle chains up to 18 micro-particles long immersed in water. The particles were optically self-arranged into a linear chain with well-separated distances between them. We observed a significant increase in the delivery speed of the whole structure as the number of particles in the chain increased. This could provide faster sample delivery in microfluidic systems. We quantified the contributions to the speed enhancement caused by the optical and hydrodynamic interactions between the particles. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3680234]