Development of a monolithic total internal reflection-based biochip utilizing a microprism array for fluorescence sensing

This paper proposes a monolithic integration method to fabricate a total-internal-reflection (TIR) based biosensor for fluorescence sensing. The monolithic TIR-based biosensor integrates a microfluidic chamber, polymer-based optics and planar waveguides into a high-throughput platform. The polymer-based optics, fabricated by SU-8 resist, include cylindrical microlenses and a microprism array for effectively conducting the excitation light into the planar waveguide. Two kinds of substrate materials, namely quartz and SU-8 resist, are used to fabricate the planar optical waveguides for efficiency comparison. To fabricate the microprism array, a technology employing glycerol-compensated oblique exposure is employed, and microprism arrays with inclined surface angles from 25 degrees to 35 degrees on the planar optical waveguide have been successfully fabricated. Multiple total internal reflection spots can be observed through this monolithically integrated optical system simultaneously. The real-time Brownian motion of fluorescent microspheres excited by the evanescent wave under this system is captured for motion analysis. The results demonstrate the feasibility of this system on the study of nanoscale phenomena. The unique fabrication and integration aspects of the monolithic biosensor including on-chip micro-optics simplify cur-rent TIR optical configurations and could potentially be integrated into a lab-on-a-chip microsystem.