This screen stores and displays encrypted images without electronics
It uses magnetic fields to display images at the same resolution as a squid’s color-changing skin.
Michigan Engineering News
Experts
Joerg Lahan
Abdon Pena-Francesch
A flexible screen inspired, in part, by squid can store and display encrypted images like a computer—using magnetic fields rather than electronics. The research is reported today in Advanced Materials by University of Michigan engineers.
“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,” said Joerg Lahann, the Wolfgang Pauli Collegiate Professor of Chemical Engineering and co-corresponding author of the study.
Video Transcription
Abdon: The main advantage of these devices is that you can still display a lot of complex information but without the need of any electronics.
Electronic displays and systems can be hacked, right? Especially for security.
So there’s been a switch to transitioning to more, um, analog physical encryption systems. In this project, we’re trying to reproduce some of the display functions that you see in the skin of squids.
Zane: Squids sometimes they flash their patterns to convey information to each other.
Abdon: In their case, but they’re using is they’re like expanding and contracting their muscles and squishing these little sacs of pigment to show, like, more of a darker or a lighter, color.
In our case, we have adopted that concept by using these particles that have two sides, one that is light and one that is dark. By giving them magnetic fields, we can control the rotation of these particles, right? And we can control which particles rotate and how they rotate.
Zane: So with the programed magnetic field we can store the magnetic information into our particle system. And with a just regular magnetic field we can show that information.
Abdon: So then we can really write and encode some complex information like images, some dynamic messages etc.,into these, flexible devices.
Zane: So this is not a conventional display but a display plus a small computer.
Abdon: Because this is all, these are encased on a, on a soft, flexible device. It’s very portable and it can be used on many different applications, right?
For like wearable sensors, for like smart IDs, you can think of this as a smart barcode that can only display information after several layers of security.
So we can program, the the message for this so that it will not only react to one specific pattern that the person A holds right. Then if person B, tries to read it, it will be nothing.
It will be like a public encrypted message. And Person see that has a different key can get a different personalized message. So this is more for protection of, of, of data, uh, in very low cost application.
Zane: Later we can expand this into more color range, maybe into RGB color channel, so that we can reveal more colors and more combinations of this encryption.
Abdon: We’re very excited about how these will change how we make, uh, display devices. We have opened a bunch of new properties and functions that they were not possible before. And it all comes from the design and engineering of these, these smart particles.
The researchers’ screen could be used wherever light and power sources are cumbersome or undesirable, including clothing, stickers, ID badges, barcodes and e-book readers. A single screen can reveal an image for everyone to see when placed near a standard magnet, or a private, encrypted image when placed over a complex array of magnets that acts 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,” said Abdon Pena-Francesch, an assistant professor of materials science and engineering and co-corresponding author. “This could also be used for color-changing surfaces, for example on camouflaged robots.”
Shaking the screen erases the display—like an Etch-A-Sketch—except the image is encoded in the magnetic properties of beads inside the screen. It returns when the display is exposed to the magnetic field again.
Video Description
A transparent, palm-sized rectangle rests on a researcher’s hand. The screen shows an orange block M on a white field. When the researcher shakes their hand, the M vanishes as the screen reverts to a mostly orange screen with some white speckles. The block M on a white field abruptly reappears after a brief moment.
The beads act like pixels by flipping between orange and white hemispheres. The orange halves of the beads contain microscopic magnetic particles that allow them to rotate up or down when exposed to a magnetic field, providing the color contrast needed to display an image.
Exposing the pixels to a magnet will program them to show either white or orange in either a pulling or pushing magnetic field—a state referred to as their polarization. For some pixels made with iron oxide magnetic particles, the polarization can be changed with relatively weak magnetic fields. But the polarization of pixels that also include neodymium particles is harder to change—a strong magnetic pulse is required.
Holding the screen over a grid of magnets with different strengths and orientations can selectively change the polarization in some parts of the screen, causing some pixels to flip white and others to flip orange under the same magnetic field orientation. This is how an image is encoded.
Then, the image can be displayed under any weak magnetic field, including a regular magnet. But because iron oxide particles can be reprogrammed with relatively weaker fields, private images can be displayed with a second magnetic grid that selectively rewrites how some areas of the screen flip. When returned to the standard magnet, the iron oxide pixels revert back to their original polarization to show the public image.
Video Description
A screen appears blank when held over a large, circular magnet in the middle of the frame. When moved to a grid of magnets to the left, an orange X appears on the screen. The X now returns to the screen when held over the center magnet. When the screen is moved to special decoding grids on the right, it shows a circle, square, and dot, but when returned to the simple magnet, it still shows an X.
Several private images can be displayed from a single public image, each with a unique key. The decoding keys can also be programmed to only work with specific encoding keys for extra security.
The team decided on the screen’s resolution by studying squids and octopi, which change color by expanding and contracting pigment sacs in their skin.
“If you make the beads too small, the changes in color become too small to see,” said Zane Zhang, a doctoral student in materials science and engineering and the study’s first author. “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.”
The research was funded by the American Chemical Society Petroleum Research Fund and the National Science Foundation.
The authors submitted an invention disclosure for the device with the help of 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.