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    Pumpless, "Self-Driven" Microfluidic Channels with Controlled Blood Flow Using an Amphiphilic Silicone

    Year: 2020

    Journal: ACS Appl. Polym. Mater., Volume 2, APR, page 1731–1738

    Authors: Dogbevi, Kokou S.; Ngo, Bryan Khai D.; Blake, Connor W.; Grunlan, Melissa A.; Cote, Gerard L.

    Organizations: National Science FoundationNational Science Foundation (NSF) [HRD-1502335]; Texas A&M Engineering Experiment Station (TEES)

    Keywords: microfluidic; pumpless; blood flow; flow control; silicone; poly(ethylene oxide); surface modifying additive

    A silicone microfluidic system that enables the pumpless, controlled flow of blood represents a significant advancement for the improvement of diagnostics and biological research. Such a system would be especially useful toward developing a single use, optical imaged point-of-care (POC) device. While readily used to prepare microfluidics via soft lithography, silicones inhibit capillary flow of blood due to their extreme hydrophobicity. Herein, Sylgard 184 was conveniently modified with a surface modifying additive (SMA) to produce microfluidics having "on-demand" surface hydrophilicity leading to pumpless capillary blood flow. The SMA is a poly(ethylene oxide) (PEO) silane amphiphile composed of a cross-linkable silane (Si-H) end group, an oligodimethylsiloxane (ODMS) tether, and PEO segment: HSi-ODMS30-block-PEO8-OCH3. The SMA was incorporated at different concentrations into the silicone (5, 7, and 14 wt %) and resulting films as well as corresponding microchannels were assessed for key properties relevant to a single use, POC device to analyze blood. Overall, the SMA did not compromise light propagation or increase autofluorescence, which are important parameters for permitting the eventual use of optical detection and imaging methods for analysis of blood within a microfluidic channel. While incorporation of the PEO-silane amphiphile SMA led to an expected decrease in modulus, this did not result in collapse of the channels. The SMA caused a dramatic increase in water-driven surface hydrophilicity, particularly at higher concentrations. As a result of the surface restructuring effect, the modified silicones enabled the pumpless flow of blood through microfluidic channels. Moreover, channel height as well as SMA concentration was useful in controlling the speed of blood flow.
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