Multiscale acoustic bubble actuators using bioinspired liquid-repellent microstructures

Abstract

Bubbles are versatile tools in applications spanning biomedicine, industry, and engineering. Their unique physical properties, such as surface tension and elasticity, as well as their strong resonance behavior, enable innovative uses in medical imaging, microfluidics, soft actuators, and microrobotics. Through acoustic actuation, bubbles exhibit high-efficiency acoustic-to-mechanical transduction, selective oscillation, and non-contact liquid manipulation. However, for the existing bubble-based systems, the programmability, stability, scalability, and multifunctionality remain the primary challenges. Here, we present acoustic bubble surfaces using bioinspired liquid-repellent microstructures, which enable programmable on-demand trapping, pumping, mixing, and high degrees of flow control. Using two-photon lithography-based 3D printing, we fabricate springtail-inspired bubble actuators in different sizes, ranging from 200 mu m to 1 mm in diameter. We demonstrate the multifunctionality feature of our proposed approach, utilizing a rectangular arrangement of bubble surfaces that enables the trapping, pumping, and mixing functionalities of the acoustic actuators in an all-in-one device. For programmability, we show actuator arrays arranged in the shape of distinct letters. Furthermore, to accommodate the multidimensionality of our approach, a 3D structure is shown on the five faces of a cube. As a real-world application, we also tested springtail-inspired bubble actuators' actuation and stability in whole blood from an animal.