Magnetic graphene oxide sheets fold, move, sense motion, and switch function by swapping magnetic layers, offering a fast, reprogrammable platform for soft robots and other morphable structures.
(Nanowerk Spotlight) Designing structures that change their form or mechanical behavior on command is a central problem in robotics and adaptive materials. Researchers are working toward sheet-like systems that bend, fold, or switch between stable shapes when exposed to a remote signal such as a magnetic field.
Some applications involve soft robots that crawl or swim by changing shape, while others involve mechanisms that alternate between compact and load-bearing states, or simple devices that store information based on physical position rather than electronics. All of these rely on materials that are lightweight, strong, simple to fabricate, and capable of being reprogrammed without needing to be rebuilt.
Traditional fabrication approaches limit how adaptable these systems can be. Casting soft polymers in molds produces flexible components, but their shape and internal magnetic pattern are fixed once they are made.
3D printing can embed magnetic particles layer by layer, yet the resulting structures usually respond in just one programmed way and changing that response often requires reprinting or heating the part to reset its magnetization. Thin films that bend when exposed to humidity or heat respond quickly but tend to weaken in water or generate forces too small for practical motion. Origami-based methods allow flat sheets to fold into complex shapes that snap or rotate, but most materials suitable for folding do not also support strong and repeatable actuation under magnetic fields.
A study published in Advanced Science (“Multifunctional and Reprogrammable Magnetoactive Graphene Oxide Origami”) introduces a sheet material designed to overcome these constraints. It folds like paper but bends and moves under moderate magnetic fields. Its stiffness changes when exposed to different humidity levels. It functions in air and water.
Most notably, its magnetization pattern can be reset by swapping thin magnetic layers instead of rebuilding the entire device. The paper demonstrates how the platform works across several types of morphable structures, including soft robots that crawl or swim, origami structures that can support loads far greater than their mass, and mechanical logic systems that switch state under programmed magnetic control.
The core of the material is a bilayer sheet. The bottom layer is made of graphene oxide, a thin carbon-based film that absorbs moisture and becomes softer as humidity increases. The top layer is a composite of graphene oxide, polyacrylic acid, and particles made of neodymium, iron, and boron. These particles retain their magnetic alignment after being exposed to a strong field, a property known as hard magnetization.
To fabricate the sheet, the composite is cast onto a graphene oxide base and peeled off once dry. The particle concentration varies from 11 to 31 percent by weight, and the final film has a mass of less than 9-milligrams-per-square-centimeter.
Microscopy confirms that the two layers bond smoothly and that the magnetic particles are distributed near the top surface. This location increases the torque that develops when the sheet’s stored magnetization interacts with an applied magnetic field.
Fabrication and characterization of magnetic graphene oxide films. a) Illustration of the preparation process of MGO films. (i) Preparation of a suspension of GO in RA/glycerol; (ii) dispersion of NdFeB particles in PAA/RA solution; (iii) mixing of GO and NdFeB suspensions; (iv) preparation of MGO films. The GO/NdFeB/PAA/RA/glycerol solution is drop-cast onto the surface of an air-dried Ca2+ cross-linked GO film. After drying the GO/NdFeB/PAA layer, a freestanding MGO film is obtained by removing the polylactic acid (PLA) mold and peeling it off from the substrate. b) SEM and EDS elemental mapping images of an MGO6 film (ϕ = 31 wt.%). Scale bar = 25 μm. c) Origami structures made byMGO films. Scale bar = 10 mm. d) Magnetically-actuated shape change of Miura-ori origami made by MGO film. (i) Schematic showing the magnetization patterns; folding of MGO Miura-ori actuated by magnetic fields generated by (ii) a permanent magnet (beneath the sample) and (iii) a Helmholtz coil. (Image: Reprinted from DOI:10.1002/advs.202514597, CC BY) (click on image to enlarge)
In a beam test, the researchers magnetized flat strips along their length and exposed them to a magnetic field at a right angle. The interaction caused the strips to bend. Beam samples with about 22 percent particle content deflected more than 70 percent of their length under a 70-millitesla field. Higher particle content added stiffness and reduced bending, so the team selected different loadings for different applications.
Humidity gives the material a second mode of control. Because graphene oxide absorbs water, the sheet becomes softer and bends more when exposed to higher humidity. The same magnetic force produces larger motion in wet conditions and smaller motion in dry settings. These effects are reversible, which means the user can tune stiffness on the fly without altering the sheet or magnetic setup.
Folding the material along creases concentrates bending at predictable locations and reduces the need for large fields. Based on these properties, the researchers selected a particle loading of 31 percent for folded structures that need more stiffness when dry but still bend well under field control.
The film can be cut and folded in minutes, and the authors used both hand tools and laser cutting to create origami structures. A Miura fold, which consists of repeating parallelogram units that allow expansion and contraction, was built from a single sheet. Once folded, the structure was magnetized while held in its compact shape. When exposed later to a magnetic field, the stored pattern caused the sheet to open and close along its creases. The team used computer models to choose magnetization layouts that would produce the desired motion, and the results matched their predictions.
Several devices illustrate how the material supports different functions. A Kresling unit, formed from a zigzag cylindrical fold, snapped between folded and expanded positions when the magnetic field direction reversed. A bellows-like Tachi Miura Polyhedron flattened or expanded under field control and held a load about 30-times its own weight when expanded. These examples show how folding patterns and magnetization act together to produce bistable, load-bearing structures without motors or hydraulics.
The platform also supports mobile robots. A Miura-based tube crawled, flipped, and rolled depending on how a handheld magnet was moved near it. The robot climbed a 10-millimeter step and cleared 25-millimeter stairs. When driven by an electromagnetic coil, an inchworm-shaped robot advanced almost 90 millimeters in 9 motion cycles, moving at about 0.43-millimeters-per-second. In water, a jellyfish-like structure pulsed its 8 arms to rise more than 41 millimeters. A small shift in magnetic alignment enabled sideways crawling at nearly 4-millimeters-per-second.
Under an applied magnetic field, the inchworm-inspired soft robot moves ≈85 mm after nine cycles of magnetic actuation at a walking velocity of ≈0.43 mm s−1. (Video: DOI:10.1002/advs.202514597, CC BY)
A key feature of the material is its ability to change function after fabrication. The team made thin magnetic stickers with preset magnetization directions. These stickers attach to the sheet with a removable adhesive. Swapping or stacking them alters the overall magnetic response without heat or solvents.
The researchers built a device with 3 Kresling cells, each storing 1 bit of mechanical state. As the field swept from 0 to 60 millitesla and then reversed, the device stepped through a scheduled sequence of folded and expanded states. Rearranging the sticker layers changed the output pattern, showing that the device could be reprogrammed without rebuilding.
In addition to actuation, the sheet can sense its own deformation. The graphene oxide layer changes its electrical resistance when bent or stretched. By connecting wires to the surface, the team recorded resistance signals that tracked the timing and degree of bending. The signals remained stable across repeated cycles. This ability to sense motion without external cameras or strain gauges supports closed-loop control systems where the device responds to its own state.
This study presents a unified material system for morphable structures that are easy to make, switch function on demand, operate in both air and water, and respond to moderate magnetic fields. The platform supports folding, force generation, real-time sensing, and post-build reprogramming through detachable magnetic layers.
Applications include soft robots that traverse uneven terrain, deployable origami that carries loads many times its own weight, and physical logic units that change state under magnetic control. The research team shows how these capabilities emerge from a single bilayer sheet, pointing to new possibilities for adaptive devices in medicine, infrastructure, underwater systems, and untethered robotics.
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