Researchers at the University of Sussex and Swansea University have applied electrical charges to manipulate liquid metal into 2D shapes such as letters and a heart.
Above – A blob of liquid metal morphs into the letter S using programmable electrical charges.
The team says the findings represent an “extremely promising” new class of materials that can be programmed to seamlessly change shape. This open up new possibilities in ‘soft robotics’ and shape-changing displays, the researcher say.
While the invention might bring to mind the film Terminator 2, in which the title character morphs out of a pool of liquid metal, the creation of 3D shapes is still some way off. More immediate applications could include reprogrammable circuit boards and conductive ink.
Yutaka Tokuda, the Research Associate working on this project at the University of Sussex, says: “This is a new class of programmable materials in a liquid state which can dynamically transform from a simple droplet shape to many other complex geometry in a controllable manner.
“While this work is in its early stages, the compelling evidence of detailed 2D control of liquid metals excites us to explore more potential applications in computer graphics, smart electronics, soft robotics and flexible displays.”
The electric fields used to shape the liquid are created by a computer, meaning that the position and shape of the liquid metal can be programmed and controlled dynamically.
Professor Sriram Subramanian, head of the INTERACT Lab at the University of Sussex, said: “Liquid metals are an extremely promising class of materials for deformable applications; their unique properties include voltage-controlled surface tension, high liquid-state conductivity and liquid-solid phase transition at room temperature.
“One of the long-term visions of us and many other researchers is to change the physical shape, appearance and functionality of any object through digital control to create intelligent, dexterous and useful objects that exceed the functionality of any current display or robot.”
The research is being presented today (17 October) at the ACM Interactive Surfaces and Spaces 2017 conference in Brighton.
A live demonstration is taking place this evening at the Jury’s Inn Brighton Waterfront from 7pm to 10pm.
This is a joint project between Sussex and Swansea funded by EPSRC on “Breaking the Glass: Multimodal, Malleable Interactive Mobile surfaces for Hands-In Interactions”.
In this paper, we demonstrate a method for the dynamic 2D transformation of liquid matter and present unique organic animations based on spatio-temporally controlled electric fields. In particular, we deploy a droplet of liquid metal (Gallium indium eutectic alloy) in a 7×7 electrode array prototype system, featuring an integrated image tracking system and a simple GUI. Exploiting the strong dependance of EGaIn’s surface tension on external electric voltages, we control multiple electrodes dynamically to manipulate the liquid metal into a fine-grained desired shape. Taking advantage of the high conductivity of liquid metals, we introduce a shape changing, reconfigurable smart circuit as an example of unique applications. We discuss system constraints and the overarching challenge of controlling liquid metals in the presence of phenomena such as splitting, self-electrode interference and finger instabilities. Finally, we reflect on the broader vision of this project and discuss our work in the context of the wider scope of programmable materials.
Previous methods were constrained the actuation of EGaIn to channels, thus restricting the interface to a non-mutable, general purpose display.
In this paper, they go beyond these limitations and propose a method for the full manipulation of liquid metals, using electrode arrays to create dynamic patterns in an open-channel set-up. This is a step forward, which opens many opportunities for creating novel exciting visio-tactile experiences, especially when liquid metals such as EGaIn are the state-changing materials.
A liquid metal blob in an electrolyte solution is highly conductive (ε 1) and highly reactive (i.e., with the electrolyte) at the same time. When the blob is not in contact with any of the electrodes, and there is no voltage applied anywhere, the charges in the electrolyte induce a uniform charge distribution on the blob’s surface. In this case, no external force is applied to the blob. However, when the blob is in contact with one of the electrodes — and a suitable voltage is applied to one or more of the other electrodes, the charge distribution in the blob gets altered due to the difference in the conductivity between the electrolyte and the liquid metal.
As a result, charge build-up occurs at the blob’s interface, an electric double-layer (EDL) is formed and each section of the interface is subject to a Coulomb-type force that causes deformation in the direction of the electric field. Starting with the pioneering work of Beni et a this phenomenon, under the name of continuous electrowetting (CEW), has been used by many authors to induce 1D motion in confined channels, bounded by conductive walls.
In this work, they explore a different situation: their liquid metal blobs are free to move in a 2D plane and are confined only by the display surface with the electrodes (at the bottom) and by the elecrolyte-air interface on top. Specifically, their goal is to maintain connectivity of liquid metal with the anode, using a set of pre-distributed voltages on one or more of the other electrodes to force the liquid metal into the desired complex shapes. To their best knowledge, there are no other computational approaches that achieve such full maneuverability for liquid metals in 2D.
Compilation of liquid metal CGI scenes in Terminator 2