Rapid controlled transport of water droplets by sunlight-powered pump

phys.org | 12/17/2018 | Staff
Celtics2212 (Posted by) Level 3
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Driven by natural or artificial sunlight, a novel "microtube pump" transports water droplets over long distances. As reported by Chinese researchers in the Journal Angewandte Chemie, the pump consists of a tube whose properties can be changed asymmetrically through irradiation. This results in capillary forces and a wettability gradient in the inner wall which work together to accelerate the water droplets to exceptional high speeds.

Modern molecular analytic and diagnostic methods generally work with tiny amounts of fluid. Microfluidic technology has also been used in synthetic processes in which reactions occur in microchannels and miniaturized instruments. In order to precisely transport such small volumes from one place to another, scientists at Tsinghua University and Beihang University in Beijing, China, have developed a "microtube pump".

Pump - Polymer - Tube - Diameter - µm

The pump consists of a polymer tube with a diameter of about 500 µm. It is made of two layers: The outer layer is polydimethylsiloxane (PDMS), which the researchers; led by Chun Li, Zhiping Xu, and Liangti Qu; mixed with reduced graphene oxide (rGO), a carbon-based nanomaterial that absorbs sunlight particularly well. This produces heat that is transmitted to the inner layer of the hose wall, which is made of poly(N-isopropylacrylamide) (PNIPAm), a polymer that forms a hydrogel at room temperature. Its polymer chains are knotted into a network that swells as it absorbs water. Above about 32 °C, the hydrogel collapses into compact spheres...
(Excerpt) Read more at: phys.org
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