A Total Internal Reflection (TIR)-Based Chip for Ultra-Sensitive Fluorescent Sensing

We report on a TIR-based chip which generates evanescent wave for ultra-sensitive fluorescent sensing. The chip is cast in PDMS using a Si mold fabricated by Si anisotropic wet etching and DRIE. Our method integrates miniaturized optical components, namely cylindrical microlens and prism into a monolithic chip; thus assembly is unnecessary, and misalignment is eliminated. The slide-format and monolithic chip can be used with both upright and inverted fluorescent microscope with flexible sample delivery platforms, i.e. flow-cell, micro-channels, etc. We have successfully demonstrated the capability of the chip in highly-sensitive imaging of tetramethylrhodamine (TMR) fluorescent dye and immobilized fluorescent nanobeads. Our miniaturized TIR-based chip could potentially serve as an evanescent excitation-based platform integrated into a micro-total analysis system (mu-TAS).