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 mu L 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 mu L 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.