Multiple optical traps with a single laser beam using a simple and inexpensive mechanical element

Abstract

An ordinary wire mesh is utilized to facilitate the creation of multiple optical traps (tweezers) for manipulation of small micron or sub-micron particles. Each of the traps formed in this manner is continuous and the entire array is amenable to easy control. Our method is simple to implement, inexpensive, and obviates the need to timeshare a laser beam among a set of positions, as is required in conventional multiple traps. We quantify the utility of our method by demonstrating that our continuous multiple traps are of essentially uniform strength. By way of illustrating the utility of our multiple traps, a single live red blood cell (RBC) of diameter ~8 µm was held at two locations on its surface; upon varying the inter-trap spacing, distortion in cell shape provides a ready means of studying the elastic properties of the RBC membrane under physiological conditions.