PDMS Microchannel Surface Modification with Teflon for Algal Lipid Research

Abstract

This paper presents a simple method for modifying the polydimethylsiloxane (PDMS) micro fluidic channels with Teflon for algal lipid research. When culturing and staining algae inside microfluidic devices, the small molecule dyes absorbed by the microchannel surface render it difficult for imaging and quantification. PDMS surface coated with Teflon-AF resists the absorption of hydrophobic dye molecules (i.e., BODIPY and Nile red) as confirmed using fluorescence microscopy. Here, we introduce a surface modification of PDMS microchannel using Teflon-AF using a procedure of filling and drying to directly treat the PDMS surface with perfluorinated materials. This method can be used to prevent the absorption of fluorescent probe and obtain clear fluorescence micrographs without background signal from absorbed dye molecules on PDMS microchannel. We confirmed that contact angle of Teflon-coated PDMS (116.4 degrees) is higher than that of unmodified PDMS (106.1 degrees) and thus more hydrophobic. Furthermore, Teflon-coated PDMS surface had similar to 80% of oxygen transfer rate compared to that of native PDMS and good transparency in all visible light regions. Based on these characteristics, we successfully validated the visualization and quantification of intracellular lipid droplets in microalgae C. reinhardtii using BODIPY. We believe that our new method will expand microfluidic applications on characterization of biological lipid with fluorescence probes and biochemical markers.