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Engineers at Princeton University have developed a novel material that can expand, reshape, and move in response to electromagnetic fields, resembling a robotic entity despite lacking traditional motors or internal mechanisms. This innovation represents a significant advancement in material science and robotics.
Researcher Glaucio Paulino, the Margareta Engman Augustine Professor of Engineering at Princeton, emphasized the transformative potential of this material, stating, “You can transition from a material to a robot, all controlled by an external magnetic field.”
In an article released on April 23 in the journal Nature, the researchers highlight their inspirations drawn from origami, leading to a creation that melds the characteristics of traditional materials with those of robotic systems. This metamaterial is crafted to exhibit unique properties determined by its structural design rather than its chemical makeup. By utilizing a combination of simple plastics and specifically engineered magnetic composites, the researchers demonstrated how a magnetic field can modify the material’s structure, enabling it to expand, move, and deform remotely.
The team has named their invention a “metabot,” effectively a metamaterial capable of altering its shape and mobility.
Minjie Chen, an associate professor of electrical and computer engineering and a contributor to the research, described the technology’s functioning: “The electromagnetic fields simultaneously transmit power and information. While each action is straightforward, the combination of these movements results in complex behavior.” He noted how this research propels the field of power electronics by enabling immediate, precise transmission of torque across distances to initiate detailed robotic actions.
The metabot comprises a network of modular cells that are symmetrical, a feature known as chirality, which contributes to its versatile performance. Tuo Zhao, a postdoctoral researcher in Paulino’s lab, remarked on the metabot’s ability to execute significant contortions—such as twisting and contracting—with minimal input.
Xuanhe Zhao, a materials and robotics expert not directly involved in the study, commented on the exciting implications of this work, stating, “This research opens up new frontiers in origami design and practical applications.” He praised the modular and chiral metamaterials for their remarkable versatility and functionality.
Davide Bigoni, a professor at the Università di Trento, highlighted the groundbreaking nature of this research, suggesting it could initiate substantial shifts in diverse fields, including soft robotics, aerospace, energy absorption, and thermal regulation technologies.
Focusing on potential robotic applications, Tuo Zhao utilized a laser lithography machine at the Princeton Materials Institute to construct a miniature metabot measuring 100 microns in height, which is slightly thicker than a human hair. The research team anticipates that similar mechanisms could eventually be used to deliver targeted medications or assist surgeons in repairing bones or tissue.
Additionally, the researchers devised a thermoregulator using the metamaterial, which transitions between light-absorbing and reflective surfaces. In testing, they successfully adjusted the material’s temperature from 27 degrees Celsius (80 degrees Fahrenheit) to 70 degrees Celsius (158 degrees Fahrenheit) under direct sunlight.
Future applications may extend to antennae, lenses, and devices interacting with various light wavelengths.
The geometry of this innovative material is fundamental to its performance; it features plastic tubes with struts designed to twist under compression. Referred to as Kresling Patterns in the realm of origami, these tubes are ingeniously connected in a way that enables twisting and compressing behaviors. By connecting two mirror-image Kresling tubes at their bases, the researchers crafted a long cylinder that allows for independent movement of either end based on directional twists.
This systematic arrangement permits each tube segment to react distinctly when influenced by precisely designed magnetic fields, resulting in complex movements as the magnetic field induces twisting or collapsing motions.
Paulino noted that chirality allows this material to behave contrary to standard physical expectations. Typically, twisting a rubber beam returns it to its original position. However, the group’s metabot demonstrates an asymmetrical response: when twisted clockwise and then counterclockwise, it behaves normally, but if twisted in the reverse order, it collapses further. This behavior mimics hysteresis, illustrating how prior influences on a system affect its responses—an occurrence prevalent in physics, engineering, and economics, which are difficult to mathematically represent.
Future directions for this metamaterial may include the reproduction of logic gate functions similar to those found in computer transistors, providing a tangible method to emulate complex behaviors such as non-commutative states.
The collaborative effort at Princeton involved several researchers: postdoctoral associate Xiangxin Dang developed simulations for investigating metamaterial deformation, graduate student Konstantinos Manos constructed the magnetic hardware, and Shixi Zang focused on experiments alongside crafting the thermoregulator in collaboration with Professor Jyotirmoy Mandal’s Optical and Thermal Design Lab.
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