Fariha Mahmood of McMaster University, alongside Anna C. Balazs and Victor V. Yashin from the University of Pittsburgh, have demonstrated the first functionally complete NAND logic gate constructed entirely within a soft material using visible light beams. Published in Nature Communications, the achievement utilizes a specially engineered hydrogel where three self-trapped light beams execute the NAND operation—a fundamental building block for all digital logic. This work, building upon prior theoretical studies by Balazs and the late Steven P. Levitan, establishes photoresponsive soft materials as a viable platform for creating autonomous, computation-capable systems and advances the field of “materials that compute.”
Materials That Compute: A New Vision
Researchers at McMaster University and the University of Pittsburgh have achieved a breakthrough in “materials that compute” by creating the first functionally complete NAND logic gate within a soft material using only visible light beams. Published in Nature Communications, the system utilizes a merocyanine-functionalized hydrogel that contracts when illuminated, causing light beams to “self-trap” and interact. This achievement demonstrates that materials can process information internally, without traditional electronic circuitry, opening possibilities for autonomous systems.
The innovative system relies on three self-trapped light beams within the hydrogel; the middle beam dims due to competition from its neighbors. This reliable interaction pattern allows for mapping a logic operation onto the soft material. Importantly, because the NAND gate is fundamental – all other digital logic gates can be built from it – this establishes soft, photoresponsive materials as a realistic platform for computation. The work builds upon earlier theoretical studies by Balazs and Levitan, envisioning materials capable of sensing, communicating, and computing.
This research isn’t intended to replace silicon processors, but rather to explore new design spaces for applications requiring independent decision-making. Potential areas include soft robotics, self-regulating medical devices, sensors in inaccessible environments, and adaptive materials. The system’s simplicity—using only light and a polymer network—highlights the possibility of creating entirely new types of computational devices that mimic the autonomy found in biological materials.
Building a Logic Gate with Light
Researchers at McMaster University and the University of Pittsburgh have successfully created the first functionally complete logic gate – a NAND gate – within a soft material using only beams of visible light. This breakthrough establishes soft, photoresponsive materials as a viable platform for autonomous, computation-capable systems, as all other digital logic gates can be built from a NAND gate. The work builds on theoretical studies envisioning materials capable of processing information without traditional electronic circuitry.
The system utilizes a merocyanine-functionalized hydrogel that contracts when illuminated, causing light beams to “self-trap” and narrow as they travel through the material. Interactions between three beams were key; a central beam is consistently dimmer due to competition from its neighbors, providing a reliable basis for mapping a logic operation onto the soft material. This reliable dimming allows the material to process inputs and determine outputs entirely through its internal dynamics, eliminating the need for external circuits.
This achievement doesn’t aim to replace silicon processors, but rather to mimic the autonomy of biological materials, opening new possibilities for applications like soft robotics, self-regulating medical devices, and sensors in inaccessible environments. The study establishes a framework for multiple logic operations within the same gel sample, as the light beams can be routed and combined without wiring, representing a significant step towards materials that can sense, compute, and respond independently.
To see these materials not only respond to light but also perform a logic operation feels like watching the material ‘think.’ It opens the door to soft systems making decisions on their own.
Fariha Mahmood
How Light Interaction Enables Logic
Researchers at McMaster University and the University of Pittsburgh have demonstrated the first functionally complete NAND logic gate within a soft material, specifically a merocyanine-functionalized hydrogel, using only beams of visible light. This breakthrough establishes soft, photoresponsive materials as a viable platform for autonomous computing systems. The gel contracts when illuminated, causing light beams to “self-trap” and interact; this interaction pattern allows the material to perform a logic operation without traditional electronic circuitry.
The system leverages the competitive behavior of light beams within the gel; two beams inhibit each other’s self-trapping ability, and this becomes more complex with three beams. A central beam is consistently dimmer due to interference from its neighbors, providing a reliable indicator for a logic operation. This “tug-of-war” allows researchers to map a Boolean logic operation onto the material’s internal dynamics, eliminating the need for wires, electrodes, or external circuits.
This research builds upon earlier theoretical work by Balazs and Levitan, envisioning materials that could sense, communicate, and compute. While not intended to compete with silicon processors in speed, the system offers potential for applications requiring independent decision-making, such as soft robotics, self-regulating medical devices, and adaptive materials. The accomplishment represents a significant step towards materials that can process information through their inherent physics and chemistry.
Potential Applications for Soft Computing
Researchers have successfully created a NAND logic gate – a fundamental building block of computing – within a soft, merocyanine-functionalized hydrogel using only beams of visible light. This achievement demonstrates that materials can process information without traditional electronic circuitry. The system relies on the self-trapping of light beams within the gel, where interactions between beams create reliable patterns allowing for the mapping of a logic operation onto the material itself – a key step toward “materials that compute”.
The innovation builds upon prior theoretical work establishing that responsive materials like gels could sense, communicate, and compute. Specifically, the gel contracts when illuminated, increasing the refractive index and causing light beams to self-trap. Interactions between three beams – where a central beam is inhibited by its neighbors – provide a consistent signal to determine the output, effectively mapping a Boolean logic operation without wires, electrodes, or external circuits.
This approach isn’t intended to compete with silicon processors, but rather offers potential for applications requiring independent decision-making in materials. This includes areas like soft robotics, self-regulating medical devices, sensors in inaccessible environments, and adaptive materials. The study establishes a framework for building computation directly into materials, opening “entirely new design spaces” and realizing a vision held by researchers for over a decade.