Microfluidic isolation and manipulation of microscopic objects using optical trap with geometric distortion

Abstract

Novel beam-based optical tweezers, employed in microfluidic devices, has enabled efficient and non-contact actuation of microscale samples. We report development of an optical isolator based on pincushion distortion introduced into astigmatic optical tweezers. While objects in the range of 1 to 5 microns (polystyrene particles and bacteria) were transported away along the curvilinear trajectories of the pincushion profile, objects in 10-20 micron range (e.g. cells) could easily be trapped in the center of the pincushion profile. This enabled efficient isolation of cell(s) from its surrounding with high spatial and temporal precision and thus opens up new possibility to control and study interaction of cells (and other microscopic objects) with surrounding objects without requiring presence or actuation of physical valves. The trapped and isolated cell(s) could be transported by maneuvering the sample stage or beam. Further, optical clearing of wide microscopic area was achieved using the distorted profile without requiring beam scanning or sample movement. The distorted tweezers was used to clear floating microscopic particles near axonal networks as well as from the top surface of retina explant. Theoretical simulation of force exerted by such beam profiles and experimental demonstration of its potential in microfluidic isolation and manipulation is discussed.