Superamphiphobic Bionic Proboscis for Contamination-Free Manipulation of Nano and Core-Shell Droplets

Manipulation of nanoliter droplets is a key step for many emerging technologies including ultracompact microfluidics devices, 3D and flexible electronic printing. Despite progress, contamination-free generation and release of nanoliter droplets by compact low-cost devices remains elusive. In the present study, inspired by butterflies' minute manipulation of fluids, the authors have engineered a superamphiphobic bionic proboscis (SAP) layout that surpasses synthetic and natural designs. The authors demonstrate the scalable fabrication of SAPs with tunable inner diameters down to 50 µm by the rapid gas-phase nanotexturing of the outer and inner surfaces of readily available hypodermic needles. Optimized SAPs achieve contamination-free manipulation of water and oil droplets down to a liquid surface tension of 26.56 mN m^-1 and a volume of 10 nL. The unique potential of this layout is showcased by the rapid and carefully controlled in-air synthesis of core-shell droplets with well-controlled compositions. These findings provide a new low-cost tool for high-precision manipulation of nanoliter droplets, offering a powerful alternative to established thermal- and electrodynamic-based devices.