Acousto-dewetting enables droplet microfluidics on superhydrophilic surfaces

Droplet microfluidics, a versatile technique for the precise manipulation of discrete droplets, has revolutionized biological and chemical research. So far, the successful implementation of droplet microfluidics necessitates the choice of non-wetting surfaces with minimal pinning forces, which hinders its broader adoptions in clinical applications. Here we report acousto-dewetting, a liquid dewetting principle that enables the three-dimensional, remotely controllable and precise operation of droplets on surfaces of any wettability, including superhydrophilic surfaces. This principle originates from the intricate interplay between acoustic streaming and droplet dynamics due to the extreme confinement of ultrasound within droplets, with an enhancement in pressure gradient of three orders of magnitude compared with traditional ultrasound-based approaches. We show that on superhydrophilic surfaces, acousto-dewetting achieves a contact line moving velocity that is two orders of magnitude higher than the previous limit and eliminates the undesired viscous film stemming from viscous dissipations. We developed a droplet microfluidics approach that achieves versatile droplet manipulation in various extreme scenarios associated with superhydrophilic surfaces, and applied it to an in vivo clinical setting for the rapid and safe removal of thrombus as well as drug delivery. In droplet microfluidic setups, droplets are driven around on a surface, which is normally hydrophobic. Now, droplet microfluidics with superhydrophilic substrates is shown to also be feasible by exploiting acoustic effects.