Underwater gas self-transportation along the femtosecond laser-written open superhydrophobic surface microchannels (< 100 µm) for bubble/gas manipulation
Abstract Underwater transportation of bubbles and gases has essential applications in manipulating and using gas, but there is still a great challenge to achieve this function at the microscopic level. Here, we report a strategy to self-transport gas along the laser-induced open superhydrophobic microchannel with a width less than 100 µm in water. The femtosecond laser can directly write superhydrophobic and underwater superaerophilic microgrooves on the polytetrafluoroethylene (PTFE) surface. In water, the single laser-induced microgroove and water medium generate a hollow microchannel. When the microchannel connects two superhydrophobic regions in water, the gas can be spontaneously transported from the small region to the large area along this hollow microchannel. The gas self-transportation can be extended to the laser-drilled microholes through a thin PTFE sheet. Anti-buoyancy unidirectional penetration is even achieved. The gas can overcome the buoyance of the bubble and spontaneously transport downward. The Laplace pressure difference drives the processes of spontaneous gas transportation and unidirectional bubble passage. We believe the property of gas self-transportation in the femtosecond laser-structured open superhydrophobic and underwater superaerophilic microgrooves/microholes has significant potential applications related to manipulating underwater gas.
