PORTLAND, Ore. Microfluidic devices sense and sort through molecules by channeling them down nanoscale pipes etched from polymer substrates. Unfortunately, the tiny channels often clog when biological materials stick to them, degrading performance.
Researchers at the Rensselaer Polytechnic Institute (RPI, Troy, N.Y.) think they have found a remedy: a material that optically switches from slippery to sticky.
When exposed to UV light, the polymer dislodges molecules stuck to its surfaces by becoming more slippery than teflon. The property enables even the most clogged microfluidic channels to be flushed clean.
The researchers predicted that the polymer will be useful for filtering specific proteins from biological fluids, which often clog the pores of conventional filters.
Polymer membranes are widely used as biological filters and in microfluidic devices, but clogged pores often shorten their usage. RPI professor Georges Belfort began investigating polymers that can change surface characteristics so that stuck materials can be flushed without using harsh solvents or resorting to complete disassembly.
The new material is based on PES (poly ether sulfon), its surface impregnated with a light-switchable molecule called spiropyran. Spiropyran is a molecular switch that can be changed from a passive, uncharged form to an active, strongly polarized molecule when exposed to UV light.
When switching to its polarized form, any stuck materials can be easily flushed away with water, according to the researchers. A second UV exposure switches it back to its nonpolar form.
RPI has patented the process of grafting spiropyran molecules onto the PES polymer.
Besides lab-on-a-chip applications, the researchers also expect the material to be used for biological filter membranes and timed release of drugs. In microfluidic devices, the material could be fabricated into nanoscale valves that either allow the passage of individual cellsor block their passage by making them stick to the valve's aperture.
The research was fund by Energy Department, National Science Foundation and RPI's Center for Biotechnology and Interdisciplinary Studies