Squid-Inspired Flexible Screen Shows Images Without Power

A new magnetic display screen, inspired by squid skin, can store and reveal encrypted images without electronics.

Researchers from the University of Michigan have developed a flexible screen that stores and displays encrypted images using magnetic fields rather than electronics. This technology, reported in Advanced Materials, represents a fascinatingly oceanic step forward in the use of mechanical materials for information processing and encryption.

Joerg Lahann, Wolfgang Pauli Collegiate Professor of Chemical Engineering and co-author of the study, remarked, “It’s one of the first times when 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.” This innovative screen can display images in various formats, making it a versatile solution for applications where light or power sources are impractical, such as on clothing, stickers, or ID badges.

The screen operates through a combination of magnetic fields and small, bead-like “pixels” that can switch between orange and white states. These beads contain magnetic particles that flip when exposed to a magnetic field, thereby encoding the images. The screen can be reset by simply shaking it, similar to an Etch-A-Sketch. Exposing the screen to a magnet reveals the stored image, which can be configured as either a public or private display depending on the magnetic key used.

“This device can be programmed to show specific information only when the right keys are provided,” said Abdon Pena-Francesch, assistant professor of materials science and engineering and co-corresponding author of the study. “And there is no code or electronics to be hacked.” This level of encryption, relying solely on magnetic fields, could offer new possibilities for secure, programmable surfaces, such as camouflaged robots or colour-changing displays.

The technology draws inspiration from the natural world, specifically squid and octopus skin. The research team studied these animals’ ability to change colour through the expansion and contraction of pigment sacs. By mimicking the size and distribution of the squid’s pigment sacs, the researchers optimized the size of their screen’s pixels for maximum contrast. “If you make the beads too small, the changes in colour become too small to see,” explained Zane Zhang, a doctoral student in materials science and engineering and the study’s first author.

The magnetic encryption system works by using different types of magnetic particles within the beads. Iron oxide particles allow for easy reprogramming with weak magnetic fields, while the inclusion of neodymium particles requires a stronger magnetic pulse to change polarization. This selective magnetism enables the encoding of both public and private images on the same screen. By holding the screen over an array of magnets with varying strengths and orientations, the polarization of specific areas can be altered, revealing different images depending on the magnetic key used.

One of the most compelling aspects of this technology is its ability to store multiple encrypted images within a single screen. Each image can only be accessed with a unique magnetic key, providing an added layer of security. This functionality could be particularly useful in situations requiring discreet information display, such as secure identification or barcodes that change based on the magnetic key applied.

You can read the full paper “Janus Swarm Metamaterials for Information Display, Memory, and Encryption” is open access in Advanced materials.