Transmission Spectrum of PDMS in 4-1 μm Mid-IR Range for Characterization of Protein Structure

摘要

Infrared spectroscopy has been an important tool to characterize secondary structure of proteins for decades. Recent advances in the miniaturization of devices for biochemical assays have embraced poly(dimethylsiloxane) as material. However, the Infrared transmission characteristics of PDMS, especially in the form of sub-mm film, are not well understood. This hampers utilization of microdevices for protein optical identification. This paper characterizes mid-infrared transmission of Dow Corning Sylgard 184 using Fourier transform infrared spectrometer. Effects of various fabrication parameters are considered, particularly the mixing ratio of base to curing agent of the pre-polymer. For typical mixing ratio of 10:1, spectral results showed two viable transmission bands with transmittance above 50%: 2500-2194 cm~(-1) and 2122-1980 cm~(-1), where the former band exhibits higher and near-constant transmittance. The transmittance is found to depend strongly on the mixing ratio; lower mixing ratio results in higher transmittance. Maximum transmittance of about 95% is found between 2490-2231 cm~(-1) with mixing ratio of 8:1. This wavenumbers range appears promising to characterize IR properties of suitable biomolecules using PDMS-based microdevices.