A compound microfluidic device with integrated optical waveguides

Abstract

ABSTRACT The integration of optical components in microfluidic devices is an emerging issue for downscaling analytical processes to lab-on-a-chip systems. Our approach is to build a one compound polymer system, which combines optical waveguides with microfluidic channels in one monolithic device. In addition the entire chip shall be optimized to use optical interfaces only. The processing of channels and waveguides is based on photodegradation of PMMA through deep ultraviolet (DUV) radiation in both cases. In a first step, microfluidic trenches with a depth of 5 µm are structured by DUV lithography with a subsequent developing process dissolving the exposed material. Waveguides, geometrically crossing the channel, get implemented by a second DUV lithography step. In a last step, the transparent optofluidic devices are covered to form channels and sealed with a second PMMA substr ate by thermal bonding. The process was optimized to achieve leakage free channels without any disturbance of the waveguide behaviour. The paper discusses the manufacturing process and shows experimental results that serve as preparation for ongoing simulations for sensing applications. In first experiments the optical attenuation of the waveguides decreased by 1.2 dB at a wavelength of O = 638 nm, when the empty channels were filled with deioni sed water which corresponds to a change in the refractive index of 0.33. Keywords: Polymer optical waveguide, integrated microoptic s, optofluidics, biophotonics, lab-on-a-chip, PMMA