Optical two-beam trap in a polymer microfluidic chip

Abstract

An optical two-beam trap, composed from two counter propagating laser beams, is an interesting setup due to ability of system to trap, hold, and stretch soft biological objects like vesicles or single cells. Because of this functionality, system was also named the optical by Jochen Guck, Josep Kas and co-workers some 15 years ago. In a favorable setup, two opposing laser beams meet with equal intensities in middle of a fluidic channel in which cells may flow past, be trapped, stretched, and allowed to move on, giving promise of a high throughput device. Yet, single beam optical traps, aka optical tweezers, by far outnumber existing optical stretchers in research labs throughout world. The ability to easily construct an optical stretcher setup in a low-cost material would possibly imply more frequent use of optical stretching technique. Here, we will outline design, production procedures, and results obtained in a fiber-based experimental setup built within an injection molded microfluidic polymer chip. The microfluidic chip is constructed with a three layer technology in which we ensure both horizontal and vertical focusing of cells we wish to trap, thereby preventing too many cells to flow below line of focus of two counter propagating laser beams that are positioned perpendicular to direction of flow of cells. Results will be compared to that from other designs from previous work in group.