Reviewed by Lexie CornerSep 17 2024
University of Michigan engineers have developed a flexible display inspired by cuttlefish that can store and reveal hidden images, functioning similarly to a computer but using magnets instead of electronics. The study was published in Advanced Materials.
Abdon Pena-Francesch, an assistant professor of materials science and engineering (left), and Zane Zhang, a doctoral student in materials science and engineering (right), view squid skin under a microscope. The researchers based the size of their screen’s pixels on the animal’s pigment sacs. Image Credit: Jeremy Little, Michigan Engineering
It’s one of the first times where mechanical materials use magnetic fields for system-level encryption, information processing, and computing. And unlike some earlier mechanical computers, this device can wrap around your wrist.
Joerg Lahann, Wolfgang Pauli Collegiate Professor and Study Co-Corresponding Author, Department of Chemical Engineering, University of Michigan
The team's screen could be applied in environments where light and power are limited, such as on clothing, stickers, ID cards, barcodes, and e-readers. The display can reveal a public image when near a standard magnet, or a hidden, encrypted image when placed over a specialized magnet array that functions like an encryption key.
This device can be programmed to show specific information only when the right keys are provided. And there is no code or electronics to be hacked. This could also be used for color-changing surfaces, for example, on camouflaged robots.
Abdon Pena-Francesch, Assistant Professor and Study Co-Corresponding Author, Department of Materials Science and Engineering, University of Michigan
Shaking the screen clears the display, similar to an Etch-A-Sketch, but the image is stored in the magnetic properties of beads inside the screen and reappears when the display is placed near a magnetic field again.
These beads function as pixels by flipping between their orange and white sides. The orange halves contain tiny magnetic particles that allow them to spin in response to a magnetic field, creating the color contrast needed for an image.
When the screen is placed near a magnet, the pixels align to display either white or orange depending on whether the magnetic field is attracting or repelling—this is known as their polarization. Pixels with iron oxide magnetic bits can change polarization with weak magnetic fields, while those with neodymium bits require a strong magnetic pulse to alter their state.
By placing the screen over a grid of magnets with varying strengths and directions, specific areas of the screen can be polarized differently, causing some pixels to display white and others orange, thus encoding an image.
Once encoded, the image can be revealed using a weak magnetic field, like that of a regular magnet. A second magnetic grid can be used to rewrite the iron oxide pixels, allowing a private image to be displayed. When returned to the original magnet, the iron oxide pixels revert to show the public image.
This system allows multiple private images to be stored and displayed from a single public image, each with its own unique decoding key. These keys can be customized to work with specific encoding keys, providing an extra layer of security.
The team designed the screen’s resolution by studying how squids and octopuses change color, mimicking their ability to expand and shrink pigment sacs in their skin.
If you make the beads too small, the changes in color become too small to see. The squid’s pigment sacs have optimized size and distribution to give high contrast, so we adapted our device’s pixels to match their size.
Zane Zhang, Doctoral Student and Study First Author, Department of Materials Science and Engineering, University of Michigan
The American Chemical Society Petroleum Research Fund and the National Science Foundation funded the research.
The authors filed an invention disclosure for the device with help from U-M Innovation Partnerships.
Lahann is also a Professor of Materials Science and Engineering, Biomedical Engineering, and Macromolecular Science and Engineering, and the Director of U-M’s Biointerfaces Institute. Pena-Francesch is also an Assistant Professor of Macromolecular Science and Engineering, Chemical Engineering, and U-M’s Robotics Institute.
A screen using magnetic pixels stores and displays encrypted images without electronics
A screen using magnetic pixels stores and displays encrypted images without electronics. Video Credit: University of Michigan
Journal Reference:
Zhang, Z., et al. (2024) Janus Swarm Metamaterials for Information Display, Memory, and Encryption. Advanced Materials. doi.org/10.1002/adma.202406149