Liquid metal engine from Australia: how a drop of metal can change robotics and medicine

The news from a laboratory at the University of Sydney reads like a page from science fiction: an engine in which nothing rotates — at least in the usual sense. The rotation is created not by a shaft or a rotor, but by internal flows in a drop of liquid metal hidden in a salt solution.

What exactly did the UNSW researchers come up with?

Manufacturers' Monthly magazine reports: a team from the University of New South Wales (UNSW) has developed a fundamentally new type of motor — a "liquid metal droplet rotary paddle motor," a rotating motor based on a drop of liquid metal.¹ It generates rotation not through rigid parts, but through circulation within the metal droplet itself under the influence of an electric field.¹

In the simplest description, it looks like this: a drop of liquid metal is placed in a salt solution, an electric field is applied to it, eddy currents arise inside, which "pick up" a small copper blade immersed in the liquid metal, and it begins to rotate.¹ That is, the engine is the drop itself, and the copper blade is only a passenger in its internal currents.

How does this engine differ from traditional ones?

A classic electric motor consists of coils, magnets, a steel shaft, bearings, a housing, and dozens of small parts. The UNSW liquid metal motor does not have this “mechanics”: there is no rigid rotor, conventional bearings, complex gearboxes, or gears.¹ The movement occurs due to controlled flows in the liquid metal, which itself becomes the working medium and the "heart" of the engine.

Project leader Dr. Priyank Kumar emphasizes: “We use the flow of liquid metal itself to create rotation without traditional moving parts. It is simple, compact and inherently flexible.”¹ Unlike rigid motors, which do not tolerate deformations of the body well, a liquid metal motor can operate in flexible structures — for example, in soft robots or implants.

Technical capabilities: 320 revolutions per minute and a new class of actuators

According to the results of experiments, the liquid metal engine is capable of reaching speeds of up to 320 revolutions per minute — a new benchmark for liquid metal-based actuators, which previously demonstrated much more modest capabilities.¹ For the field of "soft" robotics, this is more than enough: we are not talking about turbines or industrial machines, but about small, soft mechanisms that crawl, go around obstacles, or move in narrow channels.

The motor is described in an article in the journal npj Flexible Electronics, which highlights its primary purpose: integration into flexible electronics and systems where conventional motors either do not fit or break when deformed.¹ In such an environment, a simple liquid metal "mini water mill" does not look exotic, but a logical development of technology.

"Miniature water wheel": how the design works

The inventor, graduate student Richard Fuchs, compares his engine to a tiny water wheel: just as the flow of liquid pushes the blades of a wheel, internal vortices in the liquid metal push the copper blades inside the drop.¹ The difference is that here the "river" is hidden inside and is controlled by an electric field.

Structurally, the engine consists of three key components: a drop of liquid metal, the salt solution in which it "floats," and a tiny copper blade inside the metal.¹ When an electric field is applied, an electrochemical effect occurs that causes the metal to "swirl," and this internal turbulence is converted into the rotational motion of the copper blade.

Why liquid metal: advantages of the material

Liquid metals, particularly gallium-based alloys, have become laboratory stars in recent years: they conduct electricity, can change shape, self-heal from damage, and function in narrow channels where no solid component would fit.¹ In this engine, liquid metal acts as both a conductor, a working fluid, and a mechanical "carrier" of motion.

Thanks to this, the design is not tied to classical mechanics: there are no rigid shafts, no precise centering of bearings, fewer components that can wear out or jam.¹ In potentially aggressive environments—for example, in medical fluids or the human body—this is critical: any rigid, fragile mechanism would not survive there for long, whereas a drop of liquid metal is able to adapt to its surroundings.

Possible applications: from "soft" robots to implants

The article emphasizes: the potential of a liquid metal engine is especially great in areas where traditional rigid parts simply do not work. First of all, this is soft robotics - flexible, stretchable, "streamlined" robots that can pass through narrow gaps, go around organs or structures without injuring them.¹

University of Sydney Professor Kourosh Kalantar-Zadeh, who is collaborating with the UNSW team, paints a picture: "Imagine a tiny robot that can navigate narrow, uneven spaces inside the human body, powered by motors that are soft and flexible, rather than hard and brittle."¹ For endoscopic procedures, targeted drug delivery, or microsurgery, this is not a fantasy, but a completely logical next step.

Flexible electronics and microfluidic systems

In addition to robotics, a liquid metal motor could become part of flexible electronic systems — for example, wearable devices where micro-movements, vibration, or precise positioning are required, but a classic motor would be too bulky or rigid.¹ Imagine an “electronic skin” or a smart patch capable of not only measuring but also reacting — compressing, massaging, moving microcomponents.

Another direction is microfluidic systems, in which fluids move through hair-thin channels. Where traditional pumps fail, a liquid-metal motor integrated into the channel structure could create precise local flows, opening up new possibilities for labs-on-a-chip and miniature chemical reactors.¹

Medicine of the future: movement inside the body without rigid mechanisms

One of the most intriguing applications is biomedical implants. A traditional motorized implant is a constant compromise: the larger and stiffer it is, the higher the risks of inflammation, mechanical irritation, and rejection.¹ A liquid metal engine potentially allows for the creation of small systems that "adjust" to tissues, move with them, and do not cause mechanical injuries.

These include, for example, implanted pumping systems for local fluid circulation, micromechanisms inside artificial organs, or devices that can gently change their shape or position without exerting hard pressure on surrounding structures.¹ If such engines can be made biocompatible and durable, they could open up a whole new layer of medical solutions.

Challenges and limitations of technology

Despite their optimism, the UNSW team admits that this is just the first step — a prototype that demonstrates the principle.¹ Ahead are scaling, stabilizing operation in different conditions, issues of compatibility of the liquid metal with the environment and systems in which it will operate, as well as control over the accuracy and force of rotation.

In addition, liquid metal systems inevitably encounter complex electrochemical effects: electrode corrosion, changes in the composition of solutions, and the formation of oxide films can affect the stability of engine operation.¹ Engineers will have to solve these problems if they want to turn a laboratory experiment into an industrial technology.

Why this development is important for engineers and production

Manufacturers' Monthly emphasizes with good reason: rotary engines are one of the most common, but least noticeable technologies of our time.¹ They are in smartphone vibration motors, laptop fans, camera servos, washing machines, drones, industrial lines — virtually anywhere that something needs to rotate.

Any radically new approach to generating rotation could theoretically transform dozens of industries at once. If liquid metal motors find their way into even a fraction of these applications—for example, in the micro- and nanoactuators segment—it would usher in a new class of products that are currently impossible to design based on rigid mechanics.¹

What this means in the broader context of technology

The work of Australian researchers fits into a broader trend: the transition from "hard" technologies to flexible, adaptive, soft systems, where the line between mechanics, chemistry, and electronics is blurring.¹ The liquid metal becomes simultaneously a wire, a motor, and a structural element; the electric field is simultaneously a source of energy and a tool for controlling form and movement.

For Ukrainian engineers and manufacturers, such news is not only an interesting scientific story, but also a landmark: the world is moving towards the design of devices that are not afraid of deformation, work in tight spaces, and combine electronics and micromechanics in one flexible body.¹ And the liquid metal engine from the UNSW laboratory is further proof that the future of rotation may start not with a shaft, but with a drop.

Sources

1. Manufacturers' Monthly: article "Liquid metal motor spins future tech" about UNSW's development of a liquid metal droplet rotor motor, its working principle and possible applications.