Magnetic Displays Inspired by Squid Skin Reveal Encrypted Images

Researchers, inspired by the color-changing skin of squids and other cephalopods, have created a flexible screen that stores and displays encrypted images using only magnetic particles, without any electronics.

Scientists have been experimenting with metamaterials—engineered materials with unusual properties not found in nature—for some time. They have used these materials to develop innovations like invisibility cloaks and bone-penetrating ultrasound. Mechanical metamaterials, in particular, exhibit programmable behavior by combining material and structure, which enables them to perform advanced functions beyond their basic mechanical characteristics.

Advancing Information Processing

Researchers are exploring the potential of mechanical metamaterials for use in information processing and computing. However, their application is limited due to the reliance on folding, bending, and buckling mechanisms, which are challenging to miniaturize. Engineers at the University of Michigan (U-M) have now developed a flexible display screen that uses magnetic fields, rather than electronics, to reveal images—drawing inspiration from squid skin.

“This is one of the first instances where mechanical materials utilize magnetic fields for system-level encryption, information processing, and computing,” said Joerg Lahann, a U-M chemical engineering professor and co-corresponding author of the study. Abdon Pena-Francesch, assistant professor of materials science and engineering and co-author, further explains the screen’s development in the video below.

The Role of Squid Inspiration

So, how does the squid come into play? Squids and other cephalopods have specialized organs called chromatophores in their skin, which contain pigment sacs that expand and contract rapidly under muscle control. This collective movement allows squids to change their skin color and pattern for purposes like camouflage, hunting, or mating. Researchers drew inspiration from the expansion and contraction of chromatophores to determine the screen’s resolution.

“If the beads are too small, the color changes become too subtle to notice,” explained Zane Zhang, a doctoral student in materials science and engineering and the study’s lead author. “Squid pigment sacs are optimized in size and distribution for high contrast, so we designed our device’s pixels to match that size.”

The “pixels” in this system are magnetoactive Janus particles (MAJPs), nanoparticles with two distinct surfaces. Researchers created bi-compartment MAJPs with neodymium ferromagnetic microparticles and superparamagnetic iron oxide in one side, and titanium oxide pigment in the other.

Programming Pixels with Magnetic Fields

Using magnetic fields, the particles were programmed into two states—‘on’ (iron side up, orange) and ‘off’ (titanium side up, white). MAJPs with iron oxide responded to weak magnetic fields, while those with neodymium needed a stronger pulse. By placing the screen over magnets of varying strengths, the researchers controlled which pixels flipped, encoding an image.

Using Magnetic Grids to Display and Hide Images

“Iron oxide nanoparticles can be reprogrammed with weak magnetic fields. By using a secondary magnetic grid, you can selectively alter parts of the screen and display private images. Once you return the particles to the standard magnet, they reset to their original polarization, revealing the public image again.”

A single public image can hide multiple private images, each accessible only with a specific decoding key that matches a unique encoding key, enhancing security.

“This device can display particular information only when the correct keys are used,” said Pena-Francesch. “There’s no code or electronics to hack. It could also be applied to color-changing surfaces, like those on camouflaged robots.”

Similar to an Etch-A-Sketch, the classic red-framed drawing toy from the late 1950s, shaking the screen clears the display. When exposed to a magnetic field, the image reappears.

The researchers note that this screen is ideal for situations where light and power are impractical or undesirable, such as on clothing, stickers, ID badges, barcodes, and eBook readers.

Read the original article on: New Atlas

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