Proton Beam Fabricated Lab-on-a-chip for Single Molecule Detection

Abstract

Lab-on-a-chip (LOC) plays a significant role for the analysis of small volumes of biological entities. Proton beam writing (PBW) is a powerful direct-lithographic process with the ability to fabricate smooth high-aspect-walls in various polymers. For such LOC devices, a smooth microchannel improves the device's signal-to-noise-ratio by reducing the amount of scattered light. An SU-8 master mold was fabricated using PBW and the final LOC was produced using soft lithography in polydimethylsiloxane (PDMS).The device consists of a microfluidic channel, which has a dimension of 25µm (Width) by 40µm (Height) by 1cm (Length) and two aligned etched-multimode-optical-fibres embedded in PDMS. Fluorescence within the optical-fiber detection region is excited by a 488nm-laser, which was focused to the detection region by a microscope objective. The fluorescence emission from the detection region is monitored wavelength selectively by avalanche-photodiodes-detector. This LOC device is designed primarily for the purpose of single molecule detection in very low concentrations of nucleic acid tagged with quantum dots.