Characterization of an on-chip reconfigurable 3D optofluidic microlens by confocal laser scanning microscopy

Abstract

This research describes the design, fabrication and performance of an optofluidic 3D microlens reconfigurable by hydrodynamic flow rate adjustments. The microflow device is realized by standard single-layer micromachining of the photoresist SU-8 on a silicon substrate. On-chip waveguides and microgrooves designed for the insertion of multimode glass fibers are integrated to serve as optical interconnection for incident light coupling and detection. The laminar flow regime in the structured microchannel and the use of two transparent fluids with different refractive indices enable smooth optical interfaces useful for the creation of optofluidic elements. The inertial microfluidic effects occurring in the channels allow the generation of a multiconvex 3D microlens. By altering the input flow rates the lens shape with different lens radii in the lateral and normal direction is adjusted. To confirm the fluid dynamic simulations and to three-dimensionally characterize the microflow system we conducted confocal laser scanning and fluorescent sample measurements. The unique features of this optical chip offer a novel 3D light focusing system attractive for enhanced low-cost cell parameter screening without the use of bulky/expensive single photon counting units.