Octopuses and their cephalopod relatives have long fascinated biologists with their seemingly supernatural shape-shifting. Cephalopods rapidly change color and texture to blend in with their surroundings and evade predators. This natural camouflage is an amazing part of biology, and engineers have tried to recreate it with limited success. But that may be about to change.

Researchers at Penn State University announced they have developed a new hydrogel material inspired by octopus skin that can encode images directly into its structure. The imprinted image then disappears and reappears when the skin is exposed to subtle changes in temperature and surrounding solvents. The result is a “4D” synthetic smart skin that can reveal hidden images or change surface patterns.

To demonstrate the technology, the team encoded a black-and-white image of Leonardo da Vinci’s Mona Lisa into a material. At room temperature, the image is essentially invisible. However, when heat is applied, the hidden contrast becomes clearer and the image becomes clearer. Although still in the early stages of development, this material could lay the foundation for synthetic adaptive camouflage, with potential applications beyond military applications. The findings were published this week in the journal nature communications.

It’s an impressive feat of engineering that highlights the elegant complexity that nature has refined over millions of years of evolution. Even with all the resources and powers of Brian, man still cannot surpass nature’s innate artistry.

How to hide an octopus

Scientists are beginning to truly understand the complexity of the octopus’ brain and its unique problem-solving abilities. However, when it comes to shape change, the process appears to be more instinctive than intentional.

Biologically, cephalopods rely on specialized neuromuscular organs called chromatophores to perform evolutionary magic tricks. Chromophores expand and contract in response to neural signals triggered by environmental cues. They also use muscle hydrostats to rapidly change skin texture. These features give the octopus an incredibly dynamic appearance that allows it to seamlessly blend into its surroundings.

“This complex system of nerves and muscles gives soft-bodied organisms the remarkable ability to simultaneously change their optical appearance, surface texture, and shape.” The team behind this new study writes:.

Print a “newspaper” on the skin

To recreate in the lab how octopuses camouflage and change shape, the Penn State team needed a way to change both appearance and shape using a single soft synthetic material. They started by 3D printing a hydrogel to act as a canvas. The researchers first converted the image into a binary grid of pixels using a process called halftone-encoded printing. There, different patterns of 1’s and 0’s corresponded to regions of the material with different physical properties. very similar newspaper printingthe density and distribution of these pixels creates the illusion of bright and dark areas.

Once the image was converted into a binary pattern, the team encoded the image directly onto the hydrogel using controlled UV light during the printing process. In other words, the image was “baked” directly onto the hydrogel canvas. Rather than adding ink or pigment, as in tattoos, UV exposure programmed subtle differences into the material’s internal structure. Under normal conditions, these differences are not visible to the naked eye.

However, when the material is heated, the regions corresponding to the 0 and 1 patterns respond differently, gradually increasing the visual contrast. As the material reacts to its environment, previously hidden images are revealed. This process is similar to how invisible ink is exposed when a exposing solution or special light is applied. The researchers explain this as follows: Form of 4D printing Because it takes a three-dimensional object and changes its appearance over time by being exposed to external stimuli. We were also able to demonstrate the same effect by changing the surrounding solvent. This will make the hidden image visible again.

“We are printing instructions on the material,” Hongtao Sun, an industrial engineer at Pennsylvania State University and study co-author, said in the paper. Penn State University Blog Post. “These instructions tell your skin how to react when something changes in its surroundings.”

To demonstrate this effect, they first encoded the letters “PSU” into the hydrogel film. When the temperature of the film was changed, letters appeared. I then repeated the process with a grayscale image of the Mona Lisa, increasing the difficulty level. In theory, they say, the same approach could work with any image. All that is required is to convert it into a binary pattern and encode it onto the hydrogel.

This isn’t the first time scientists have drawn inspiration from octopus anatomy. Rutgers University Engineer 2021 Created 3D printed artificial muscles When exposed to light, its shape changes slightly. Recently, researchers at Stanford University developed Flexible synthetic material that expands When exposed to an electron beam, the size changes. Elsewhere, roboticists are even developing robots that look a little scary, like octopuses. ”tentacle bot” It is equipped with mechanical troops and suction cups that help it move around and grab objects.