Realization of Self‐Rotating Droplets Based on Liquid Metal

Abstract

Owing to their fascinating characteristics, liquid metals (LMs) have attracted increasing attention from the scientific community, and are a potential material for various applications. A novel phenomenon is reported in which an acid droplet spontaneously rotates on the surface of an LM. The experimental results show that this phenomenon originates from the collective motion of bubbles generated by the chemical reactions between the droplet and the LM. The angular velocity of the droplet rotation is on the order of 101 rad s−1, which is much higher than that driven by other mechanisms. Under different conditions, the period of the droplet differs, and it increases with the pH and radius of the acid droplet. The theoretical results indicate the dominant factors and the characterized angular velocity, which agree well with the experimental data. This phenomenon demonstrate that the general particles can also induce special spatial–temporal patterns, and opens up a new field for the application of LMs.

Spontaneous Motion and Rotation of Acid Droplets on the Surface of a Liquid Metal

“…59 With a comma shape, the droplet can rotate continuously under the action of an unbalanced Laplace force. 4,64,65 The process of comma shape formation is illustrated in Figure 5. In most cases, the droplet extends outward everywhere along the contact line just like the case in Figure 5a.…”

“…66 From previous work, the emergence and the collective motion of bubbles play an important role in the process of comma shape formation. 64 However, the movements and distribution of bubbles inside the droplet are not clear. Here, this issue is introduced and discussed.…”

“…The formation of a comma shape of the droplet can be divided into four stages, including the initial stage, deformation stage, direction finding stage, and direction determination stage . With a comma shape, the droplet can rotate continuously under the action of an unbalanced Laplace force. ,, The process of comma shape formation is illustrated in Figure . In most cases, the droplet extends outward everywhere along the contact line just like the case in Figure a.…”

3D actuation of foam-core liquid metal droplets

“…Other groups also investigate the vertical jumping of LM droplets in an electrolyte controlled by electrochemical oxidation and reduction; 33,34 such a method only allows instant vertical movement without the ability to provide continuous and precise 3D actuation. Moreover, by employing an acid droplet and liquid metal, the spontaneous and steady rotation of droplets is achieved, 35,36 which provides a new route for the design of potential applications (e.g., micro-and nanodevices).…”

Conversion of Polymer Surfaces into Nonwetting Substrates for Liquid Metal Applications

“…Compared with solid conductive substrates, such as copper, liquid metals allow the fabrication of conductive structures, at milli, micron, and sub-micron scales, that can be flexible, stretchable, and deformable while retaining its conductivity. Recent research shows that gallium-based liquid metals have been used to develop soft flexible and stretchable electronics, , radio-frequency (RF) antennas, − switches, − rotating liquid drops, , frequency selective surfaces, − three-dimensional (3D)-printed structures, − and composites. − …”