Forget neural networks: Scientists at the University of Reading have taught a simple hydrogel to play the 1970s game Pong, which, for those unfamiliar, is a very simple version of table tennis (ping-pong). The discovery, published in the journal Cell Reports Physical Science, could pave the way for a new era of adaptive, responsive “smart” materials.
In simple terms, here's how it works: The hydrogel's ability to learn comes from its own “memory” that appears to be based on the movement of charged particles within its structure. The researchers believe that when stimulated with electrical signals that correspond to movements in a game of Pong, these charged particles adjust their position, effectively encoding information about the state of the game, allowing the hydrogel to “remember” its previous experience and adapt its behavior accordingly. With repeated play, the hydrogel refines its control of the virtual paddle, demonstrating basic learning and an improved ability to return the ball.
“Ionic hydrogels can achieve memory mechanisms similar to those found in more complex neural networks,” said first author Vincent Strong, a robotics engineer at the University of Reading. “We've demonstrated that not only can hydrogels play Pong, but they can actually get better at it over time.”
Hydrogels demonstrate simple learning mechanism
“Our work shows that even very simple materials can exhibit complex, adaptive behaviors typically associated with biological systems and advanced AI,” Dr. Hayashi, a biomedical engineer in the School of Biological Sciences at the University of Reading, said in a press release. “This opens up exciting possibilities for developing new types of 'smart' materials that can learn and adapt to their environment.”
This discovery is remarkable because it opens up the possibility of developing new, simpler, adaptive materials that can learn and respond to their environment. Unlike traditional neural networks, which rely on complex computational models inspired by the neuronal structure of the brain, this hydrogel learns through physical and chemical processes within the material itself. This could lead to a new paradigm for simpler, more energy-efficient adaptive systems for specific applications.
The Potential of Hydrogels in Cardiac Research
Lin's team has demonstrated how different hydrogel materials can be made to beat in sync with the rhythm of an external pacemaker, and this early-stage work marks the first time this has been accomplished using materials other than living cells.
“This is an important step towards developing a myocardial model that may be used in the future to study the interplay between mechanical and chemical signals in the human heart,” said Dr. Lin. “It opens up the exciting possibility of replacing some animal experiments in cardiac research with chemically driven gel models.”
The researchers found that by subjecting the gel to periodic compression, they could entrain the gel's chemical oscillations to a mechanical rhythm. Interestingly, the gel retained a memory of this synchronized beat even after the mechanical pacemaker was turned off.
Dr Tunde Geher Herceg, lead author of the study, said the discovery could provide a new way of investigating arrhythmias, which affect more than two million people in the UK and cause the heart to beat too fast, too slow or irregularly.
She said: “Arrhythmias can be managed with drugs or electronic pacemakers, but the complexity of biological heart cells makes it difficult to study the underlying mechanical systems independently of the heart's chemical and electrical systems.”
“Our findings may lead to new discoveries and potential treatments for arrhythmias, and also help us understand how artificial materials can be used instead of animals or biological tissues in future research and treatments.”
The Future of Adaptive Hydrogels
By developing alternative experimental models to advance cardiac research, these hydrogel materials may also reduce the use of animals in medical research and provide a more ethical and efficient approach to understanding and treating heart disease. Lin explained the basic principle in a press release: “The fundamental principle of both neurons and hydrogels is that the movement and distribution of ions serves as a memory function that correlates with the sensory-motor loop of the Pong's world. In neurons, ions flow inside the cell. In gels, ions flow outside the cell.”