Droplet/bubble manipulation on a biomimetic material with low friction

The controllable transport of fluids as well as bubbles is the cornerstone of various bioprocesses and microporous technology applications, with a wide range of applications in microfluidics, bioassays, gas transport, and oil–water separation technologies. Although functional modulation of solid surfaces to achieve different surface responses for directional manipulation of microfluidics has been extensively investigated, non-contact bubble/droplet directional manipulation remains a challenge in this field. Here, we report a simple candle soot deposition method to construct oil-filled surface nanoroughness, achieve the combination of oil-locking performance and photothermal response performance on the polydimethylsiloxane (PDMS) surface, and produce a near-infrared light (NIL)-responsive soot nanoskeleton oil-filled surface (NSNOS), which can be effectively applied to the directional manipulation of droplets and bubbles. Soot nanoparticles act as a backbone to support the SiO₂ shell to provide structural stability, whereas Fe₃O₄ nanoparticles combine to provide the surface with excellent NIL photothermal response properties. It can be heated to more than 150 °C within 60 s. Precise droplet/bubble orientation manipulation is thus achieved. Through the localized thermal response to near-infrared light, we can control droplets and bubbles to achieve anti-gravity and anti-buoyancy motions with precise, controllable trajectories. We believe that this work provides important insights for the development of smart droplet/bubble micromanipulation.