Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient.In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. 
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