Triboelectric 'electrostatic tweezers' for manipulating droplets on lubricated slippery surfaces prepared by femtosecond laser processing

The use of 'Electrostatic tweezers' is a promising tool for droplet manipulation, but it faces many limitations in manipulating droplets on superhydrophobic surfaces. Here, we achieve noncontact and multifunctional droplet manipulation on Nepenthes-inspired lubricated slippery surfaces via triboelectric electrostatic tweezers (TETs). The TET manipulation of droplets on a slippery surface has many advantages over electrostatic droplet manipulation on a superhydrophobic surface. The electrostatic field induces the redistribution of the charges inside the neutral droplet, which causes the triboelectric charged rod to drive the droplet to move forward under the electrostatic force. Positively or negatively charged droplets can also be driven by TET based on electrostatic attraction and repulsion. TET enables us to manipulate droplets under diverse conditions, including anti-gravity climb, suspended droplets, corrosive liquids, low-surface-tension liquids (e.g. ethanol with a surface tension of 22.3 mN center dot m-1), different droplet volumes (from 100 nl to 0.5 ml), passing through narrow slits, sliding over damaged areas, on various solid substrates, and even droplets in an enclosed system. Various droplet-related applications, such as motion guidance, motion switching, droplet-based microreactions, surface cleaning, surface defogging, liquid sorting, and cell labeling, can be easily achieved with TETs. Nepenthes-inspired lubricated slippery surfaces are prepared by a femtosecond laser.Droplet on the slippery surface can be manipulated by triboelectric charged rod. (3) Electrostatic tweezer is designed for achieving multifunctional droplet manipulation.Electrostatic tweezer enables manipulate droplets under diverse conditions.Various droplet-related applications can be achieved with electrostatic tweezer.