Superhydrophobic micro-tube fabricated via one-step plasma polymerization for lossless droplet transfer

Lossless droplet transfer via micro-tube is urgently demanded in the fields of microfluidics and biomedicine. However, as the core component for the construction of lossless droplet transfer platform, the fabrication of low-adhesion micro-tubes is still a longstanding challenge. To solve the problems such as complex reaction procedures, difficult-to-clean reaction products, non-uniform wettability , etc. during the synthesis of the low-adhesion micro-tubes, a new one-step approach for the preparation of superhydrophobic micro-tubes has been developed, with the help of atmospheric pressure cold plasma (APCP) deposition technology. This method can break through the limitations of micro-tube materials, and achieve the preparation of superhydrophobic surface in glass and transparent Teflon tubes using a lab-made plasma generator . The mechanism of the superhydrophobic surface preparation by APCP deposition involves the formation of a micro-nano composite structure and hydrophobic functional groups. The results point out that the inner wall of the superhydrophobic micro-tube has good and consistent wettability, and uniform morphology. The reduction in transparency of the micro-tube was less than 5% within the wavelength range of 400 nm~1100 nm. Using the as-prepared superhydrophobic micro-tube as the core component, the lossless droplet transfer platform based on the non-contact ultrasonic driving was set up. Finally, the lossless droplet transfer under extreme conditions like in vertical micro-tubes, curve micro-tubes, spiral micro-tubes, using high-speed liquid feed at 850 μL/min was successfully achieved, with the transportation distance reaching hundreds of millimeters. With excellent performances, the lossless droplet transfer platform promises great potential applications in the fields like microfluidics, biomedicine and advanced device design.