Magnetic Liquid Metals Manipulated in the Three-Dimensional Free Space

Abstract

In the present study, a magnetic liquid metal droplet (MLMD), which can be stretched in large scales both horizontally and vertically in the free space, is introduced. This MLMD is fabricated based on a multimaterial system including liquid metals, iron particles, and electrolytes. Such remarkable stretching capacity is reversible, longlasting, and can be repeated for multiple times. The seemingly contrary properties, the good stretchability and the mechanic strength for threedimensional (3D) stretch, should owe to the surface oxide over the MLMD. On the basis of the 3D stretching ability of the MLMD, an intelligent scalable conductor was achieved, which can make electrical connections at various directions in the 3D free space. Moreover, the vertically stretched MLMD can move horizontally with its half body in the solution and the other half in the air, which resembles the nature of an upright walking amphibian. All the behaviors can be precisely, conveniently, and contactlessly controlled by the magnetic field provided by permanent magnets. With all the appealing properties, this MLMD presents a fundamental and promising platform for the liquid metals to further develop the multifreedom actuation in free space and eventually lead to the dynamically reconfigurable intelligent and biomimetic soft robots in the future.

Liquid Metal–Based Soft Microfluidics

“…The LM droplet was found to be more efficient for actuation in acidic solution than that in alkaline solution, perhaps due to the higher surface charge density of the EDL (Figure b). Similar to the electrical field, magnetic field actuated LM droplets were also proposed in recent years by integration of magnetic materials into LM …”

“…Similar to the electrical field, magnetic field actuated LM droplets were also proposed in recent years by integration of magnetic materials into LM. [126,[141][142][143] Ultrasound Propelled LM Robots: Control and actuation of objects by means of ultrasound have attracted increasingly attention during the past years. The tiny agents (droplets) suspended in solution are propelled by the acoustic radiation forces, which generate both the primary radiation force (responsible for the migration of the agents) and the secondary radiation force (responsible for the repulsion and attraction between the agents).…”

Ferrofluid Droplets as Liquid Microrobots with Multiple Deformabilities

“…In refs. [17–20], the movements of droplets in various conditions and with different geometrical configurations, such as a round petri dish and circular narrow channels, were observed and recorded. Moreover, in the multiple droplets system, the separation and coalescence of the droplets can be realized, which makes their behavior more complicated and charming.…”

3D Manipulation of Magnetic Liquid Metals

“…[23] Manipulating LMs as flexibly and freely as in the movie Terminator has long been a dream for many scientists across a range of scientific and technological disciplines, ranging from mechanics to biology. [24] Tremendous progress in controlling the locomotion and deformation of LMs has been demonstrated experimentally. [25][26][27][28] Among them, the actuating method of LMs via the application of an external electric field is the most investigated approach, [29][30][31] and one that has led to remarkable progress.…”