Driven by natural or artificial sunlight, a novel “microtube pump” transports water droplets over long distances. As reported by Chinese researchers in the JournalAngewandte 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”.
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石墨烯氧化物(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聚合物链are knotted into a network that swells as it absorbs水。高于约32℃，水凝胶坍塌成使内壁疏水的紧凑型球体。这也使内层收缩，使得管的内径更大。
仅在一端照射管在内壁中形成润湿性的梯度。另外，管的几何形状变得不对称，因为内径仅在辐照端增加。毛细力引起水滴to move toward the smaller diameter end – the end that is not irradiated. The decreased wettability of the inner wall at the irradiated end further accelerates the water droplet. The synergy of these two mechanisms results in high speeds, which can be controlled by changing the intensity of the irradiation. After irradiation, the tube cools off very quickly. The hydrogel returns to its original state, ready to be irradiated again.
The柔性材料允许生产米长的直线或弯曲管，其可以在长距离连续运输水。还可以使分支系统能够在不同位置同时照射或依次进行辐射。例如，这允许含有不同试剂的单个液滴以特定顺序和组合传输 - 并且可以用于诊断测试或水时dropletsserve as microreactors for chemical reactions.
Filed Under:Product design
