Magnetic Responsive On-Site Switching of the Directional Droplet Self-Transport in Shape Memory Slippery Tube

The phenomenon of controlled droplet transport has promising application prospects in various fields. Active droplet transport mode is controllable through continuous external stimuli. By contrast, self-transport is a more environmentally friendly and energy-efficient passive transport mode but lacks controllability. In this study, controlled self-transport is achieved by constructing a shape memory polymer (SMP) tube with a lubricated magnetic-responsive gel inner surface. The asymmetrical shape of the tube, combined with the lubricated inner surface, enables directional self-transport of droplets without external stimuli. Furthermore, the resistance on the inner gel surface can be altered by regulating the magnetic field to achieve effective active control during the self-transport process. Thus, smart in situ control of droplet transport can be achieved by integrating the macroscale shape variation of the tube with the dynamic control of the inner surface microstructure. Owing to the fast magnetic responsivity and in situ controllability of the self-transport process, the SMP lubricated tube demonstrates the ability to transport a variety of liquids and can be designed as a micro-reactor for step-by-step droplet detection. The findings of this study may provide guidance for the development of intelligent interface materials and microfluidic devices.