Parylene-coating in PDMS microfluidic channels prevents the absorption of fluorescent dyes

Absorption of fluorescent molecules is a troublesome property of microfluidic devices fabricated with PDMS. The absorption raises background-levels of fluorescence from PDMS, and reduces concentrations of injected fluorescent molecules in PDMS channels. We report here that conformal deposition of poly-p-xylylene derivatives (parylenes) on the surface of PDMS substantially suppressed the absorption of Rhodamine B. In a test of this technique, we found parylene-coated PDMS channels to be useful in accurate analyses using fluorescence intensity.