What Are Shape-Shifting Robots?

Inspired by the sea cucumber’s ability to melt on demand, these small-scale machines can phase-change from solid to liquid — then back again.

Written by Brooke Becher
Published on Oct. 24, 2023
What Are Shape-Shifting Robots?
Image: Shutterstock

Shape-shifting robots are reconfigurable machines capable of changing their physical state in response to an external stimulus. They’re made up of phase-changing materials, like magnetic metallic alloys, which enable them to morph from a solid to a liquid, and vice versa, when exposed to external changes.

What is a Shape-shifting Robot?

A shape-shifting robot is a stimuli-responsive machine made up of phase-changing materials.

Development of shape-shifting robots is in the early stages; however, a breakthrough study revealed that a team of researchers from Sun Yat-sen University and Carnegie Mellon University have created tiny, shape-shifting robots inspired by the anatomy of sea cucumbers. Known as magnetoactive phase transitional matter (MPTM), the novel material, made up of magnetic particles embedded in liquid metal, can liquefy and coalesce back together — sort of like the villain in Terminator 2.

These miniature machines can move quickly, jump, climb walls and split into pieces that work as a team to move objects before merging back together. They can also hold a high mechanical strength able to bear payloads more than 30 kilograms, as well as form structural or electrical connections, kind of like a conductive glue. These unique properties make shape-shifting robots a potential game changer for autonomous applications where compactness is key.

“This technology introduces new capabilities to achieve robotic functions at the small scale in hard-to-reach places,” said one of the study’s senior authors Carmel Majidi, a professor of mechanical engineering at Carnegie Mellon University, where he also directs its Soft Machines Lab. “Because of its shape-shifting properties and response to external stimuli, it can be operated remotely and controlled to move within otherwise hard to reach parts, such as those within the body.”

Such capabilities, Majidi told Built In, have the potential for transformative impact in healthcare technologies — such as foreign body removal and targeted drug delivery — as well as soft and flexible electronic circuits and small-scale robotic systems.

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A Lego-man-shaped minifigure liquifies and reforms to escape its cage. | Video: Breaking Science News

How Do Shape-Shifting Robots Work?

Shape-shifting robots are composed of phase-changing materials that absorb latent heat, which allows them to take on different states. This transformation is instigated by an external source — such as changes in a surrounding magnetic field, an electrical field or temperature — that is remotely controlled.

This unique ability to transform from one state to another is in contrast to other robotic models, like origami-inspired designs or motorized transformations, that may simply self-construct or re-orient into a new design.

Shape shifting can be achieved with an electronic-based (or machine-based) approach, or a material-based approach, according to Lining Yao, director of Carnegie Mellon University’s Morphing Matter Lab.

“Often, [shape-shifting robots] are engineered to respond to specific stimuli,” Yao said, “harnessing the energy and turning this into mechanical energy that enables either shape transformation or locomotion.”

In the landmark study, Majidi and his team of researchers went with low-melting-point metals — primarily gallium — mixed with particles that can generate their own magnetic fields.

They then applied an electromagnetic field, and created changes by rapidly alternating it. This external stimuli triggers the magnetic particles to generate an electric current, causing the metal to melt. (For reference, this study featured neodymium-iron-boron microparticles with a low melting point of 29.8 degrees celsius, similar to the temperature of a hot summer day.) During this phase change, the metallic body becomes pliable as its material’s stiffness and deformability changes.

These particles also contribute to creating a “shape-shifting” effect as they move about within the material. By manipulating the external stimulus, these mechanical devices can move, morph, divide or fuse together as the molten state of the surrounding metal warps. This ability to physically transition from solid to liquid — then back again — not only transforms a robot’s shape, but also its function.

“Form is function,” Yao told Built In. “So if we can dynamically control the shapes, we can achieve multi-functional, adaptive and responsive systems that have broad applicability in different fields.”

This spans from biomedical engineering and robotics to design, architecture and physically embodied artificial intelligence systems, she added.

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Applications for Shape-Shifting Robots

An MPTM robot demonstrates directed drug delivery. | Video: Science X: Phys.org, Medical Xpress, Tech Xplore

Drug Delivery

The high maneuverability and remote control capabilities make MPTM shape-shifting robots an ideal directed-drug delivery vehicle. This minimally invasive method of treatment, being explored on the nanoscale, aims to deliver a high concentration of a drug to a targeted site within a patient, like cancerous cells within a liver, while minimizing side effects and establishing greater control of overall toxicity released by the medicine.

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Three smart-soldering robots work as a team to repair a circuit. | Video: Science X: Phys.org, Medical Xpress, Tech Xplo

Assembly and Repair

Shape-shifting robots can also assist in construction projects. As “smart soldering machines,” they can ooze into hard-to-reach circuits, acting as both solder and conductor, in wireless circuit assembly and repair. They can also melt into threaded sockets and solidify, effectively morphing into a universal screw — no additional hardware or labor required.

 

A shape-shifting robot demonstrates how it would capture a foreign body to remove it from a patient. | Video: ScienceAle

Foreign Object Removal

Another primary pursuit for shape-shifting robots will be in biomedicine, removing foreign objects from the body. During this minimally invasive process, a patient ingests one of these miniature magnetic machines like a pill, where it locates the foreign object, and — with the aid of induction heating — molds around it, grabbing onto it like a custom-fit claw. As one, the foreign object and shape-shifting machine exit the body naturally as a waste product.

 

Inspired by the Erodium seed, the E-seed self buries when triggered by rain. | Morphing Matter Lab

Reforestation

Shape-shifting robots can also be made out of organic materials, like a bio-inspired seed carrier that buries itself into soil when cued by rain. Developed by Yao’s team at the Morphing Matter Lab, the biodegradable robot harnesses renewable energy from the environment when they shape shift, as a way to automate reforestation.

 

Frequently Asked Questions

Shape-shifting robots are made out of materials that autonomously react when activated by certain stimuli. Depending on their design, these phase-changing machines may be triggered by fluctuations in the surrounding magnetic field or temperature.

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