Droplet Manipulation: Magically Cut Apart Microdroplet by Smart Nanofibrils Wire

A strategy of droplet manipulation is introduced, that is, an ethanol-wetted nanofibrils wire (ENW) that can smartly generate a repellent force to cut apart a spreading water droplet to split droplets (SDs) on a superhydrophilic surface without any contact. The repellent force is attributed to a unique Marangoni state inside droplet due to the interaction between vapor–liquid interfaces, along with the gradient surface tension formed between the ENW and spreading droplet. It is demonstrated that such an ENW makes an as-spreading water droplet with volume of 5–25 µL to be accurately cut apart into tiny SDs in various proportions (e.g., 1/9–1/1) without loss, and the minimum SD can be 1.7 µL in volume. A spreading droplet can be one-step cut apart into patterns and further some micro-reactors can be achieved by using ENW manipulations, respectively. This finding offers insights into the design of novel droplet-manipulating materials that can be extended into microfluidics, microreactors, and others.