(Nanowerk Spotlight) As technology advances toward flexible, adaptive devices, traditional electronics are hitting their limits due to rigidity and power demands. But what if materials themselves could compute, store, and encrypt data—without relying on circuits or chips? This is the potential unlocked by programmable metamaterials like magnetoactive Janus particles (MAJPs), which are engineered to process environmental signals and adapt their behavior in real time. These particles are part of a growing movement in materials science that aims to revolutionize soft robotics, wearables, and secure communication systems by embedding intelligence directly into the physical world.
Attempts to build computational capabilities into materials have been hampered by rigid architectures and reliance on mechanical deformations like folding or bending to store and manipulate information. These approaches, though inventive, are often bulky and lack the flexibility required for miniaturized or wearable devices.
A breakthrough, however, is emerging from the study of nature’s most adaptable systems. Cephalopods, such as octopuses, are known for their ability to change skin color and patterns instantaneously. Their sophisticated control over skin pigmentation, achieved through specialized cells called chromatophores, has inspired scientists to develop a new class of materials that mimic these dynamic, programmable behaviors.
This is where magnetoactive Janus particles (MAJPs) come in. These tiny particles, engineered with distinct magnetic and optical properties, can be controlled using external magnetic fields. Much like chromatophores, they can reconfigure themselves to produce complex visual patterns, store information, and even perform basic computational tasks. MAJPs are capable of swarming together, responding in concert to magnetic fields, and enabling a range of applications, from flexible displays to secure communication systems. Unlike their mechanical predecessors, MAJPs do not rely on predefined physical states. Their ability to dynamically respond and reconfigure in real time makes them a powerful tool for creating soft, flexible devices that are untethered from rigid electronics.
A recent study at the University of Michigan (Advanced Materials, “Janus Swarm Metamaterials for Information Display, Memory, and Encryption”) showcases the potential of MAJPs in a variety of applications. These particles are composed of two distinct compartments: one that contains magnetic nanoparticles, enabling them to respond to external magnetic fields, and another that contains pigment, providing the particles with high-contrast color. When exposed to a magnetic field, the Janus particles realign themselves, switching between different visual states in a fully reversible process. The magnetic properties of these particles can be fine-tuned to allow for specific behaviors, such as memory storage or encryption.
Fabrication of magnetoactive Janus particles (MAJPs) and display system. a) Electrohydrodynamic (EHD) co-jetting to fabricate bicompartmental PLGA fibers with magnetic particles and white pigment, followed by microsectioning to slice into biphasic cylinders. b) Shape transformation from Janus cylinders to particles through surface energy minimization. c) Flexible MAJP swarm display system. d) Magnetic actuation of MAJP swarms exhibiting two color states under opposed magnetic field. e) High contrast between the two swarm states. (Image: Reproduced from DOI:10.1002/adma.202406149, CC BY) (click on image to enlarge)
One of the key innovations demonstrated by the team is the ability to program the collective behavior of these particles to form swarms that act in unison. This swarm behavior allows for more complex functions than simple binary states. By controlling the direction and intensity of a magnetic field, the researchers were able to manipulate the particles to display different colors, generate dynamic patterns, and store data. This capability is particularly significant for technologies that need to operate without relying on electronics, such as soft robotics or wearable devices, where flexibility, low power consumption, and adaptability are crucial.
Traditional displays, such as those found in phones and laptops, rely on backlighting to make images visible, consuming significant amounts of energy. By contrast, the MAJP-based displays developed in this research are non-emissive, meaning they rely solely on ambient light. The particles only require magnetic fields to shift between color states, which makes them highly energy-efficient. This opens the door to a new class of portable, low-power devices that could find use in wearable tech, where both power and space are at a premium.
Another major advancement presented in the study is the ability of MAJPs to store and process information. The researchers designed MAJPs to serve as memory units, which can hold information in both volatile and non-volatile forms. Volatile memory is similar to the RAM in a computer, which retains data only while power is supplied. In this case, the MAJP swarms retain information as long as the magnetic field is applied. When the field is removed, the data is lost.
Non-volatile memory, on the other hand, retains its stored information even when the external field is turned off, offering a more permanent solution. This dual functionality enables MAJPs to operate in environments where traditional electronic storage might fail, such as in unstable conditions or flexible, wearable applications.
Zhang’s team also explored how these particles could be used to perform basic computational tasks through Boolean logic, the building blocks of digital circuits. By combining different types of Janus particles with varied magnetic properties, the researchers created swarms that could function as logic gates, such as “AND” and “OR” gates. This ability to perform logic functions using a swarm of particles has broad implications for the development of mechanical computing systems that do not rely on conventional electronics, offering a potential alternative for systems where electronics are impractical.
Perhaps the most intriguing application of these particles lies in their potential for encryption. Security is paramount in fields ranging from digital communications to defense, and the MAJP swarms introduce a novel method for encoding sensitive information. The researchers demonstrated a process in which an external magnetic field could be used to arrange the particles into a pattern that represented encrypted data. This data could only be decrypted with a corresponding magnetic field that realigned the particles to reveal the original message.
The particles act as both the medium for storing the information and the mechanism for encoding and decoding it, providing a secure and flexible approach to data protection. This method is particularly promising for anti-counterfeiting technologies, where the ability to hide and reveal information dynamically is critical.
Swarming display and memory functions. a) MAJP swarm display with static patterns under preprogrammed structured magnetic fields. b) Dynamic MAJP swarm display patterns under structured rotating fields. c) Semi-volatile and d) non-volatile memory of structured display patterns, showing loss and conservation of encoded information respectively. e) Integration of a soft MAJP swarm display device on a glove, showing the recovery of encoded non-volatile information after mechanical agitation. (Image: Reproduced from DOI:10.1002/adma.202406149, CC BY) (click on image to enlarge)
In one of their demonstrations, the team encoded a seemingly random pattern in the particles. When read under the wrong magnetic field, the pattern remained indecipherable. However, when the correct decryption key—a complementary magnetic field—was applied, the particles reoriented themselves into a readable message. This two-key encryption system, similar to the XOR function in digital logic, adds an extra layer of security that is hard to replicate, offering new possibilities for secure communications and information storage.
Despite the promise of this technology, there are still hurdles to overcome. The resolution of the displays is currently limited by the size of the individual particles, and the process of scaling these systems up for widespread use remains a challenge. However, the modular and adaptable nature of MAJPs suggests that these limitations could be addressed with further research and development. As these particles can be tuned for specific applications, it is easy to envision their use in everything from smart textiles to medical devices, where traditional rigid electronics would be too cumbersome.
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