Move over, neural networks. Scientists at the University of Reading have taught a simple hydrogel to play the 1970s game Pong, which, for those unfamiliar, is something like an uber-simple game of table tennis (pingpong). The discovery, published in Cell Reports Physical Science, could pave the way to a new era of ‘smart’ materials that are adaptive and responsive.

Here’s how it works in a nutshell: The hydrogel’s learning ability stems from its unique “memory” that is likely based on by the movement of charged particles within its structure. The researchers believe that, when stimulated with electrical signals corresponding to the actions in the Pong game, these charged particles adjust their positions, effectively encoding information about the game’s state, allowing the hydrogel to “remember” previous experiences and adapt its behavior accordingly. Over repeated rounds of play, the hydrogel refines its control over the virtual paddle, demonstrating a rudimentary form of learning and an improvement in its ability to return the ball.

Hydrogel demonstrates simple learning mechanism

“Our research shows that even very simple materials can exhibit complex, adaptive behaviours typically associated with living systems or sophisticated AI,” said Dr Hayashi, a biomedical engineer at the University of Reading’s School of Biological Sciences, 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 noteworthy because it opens up possibilities for 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 brain’s neuronal structure, this hydrogel learns through the physical and chemical processes within the material itself. This could lead to a new paradigm of simpler, more energy-efficient adaptive systems for specific applications.

Hydrogel’s potential in cardiac research

Hayashi’s team demonstrated how a different hydrogel material can be taught to beat in rhythm with an external pacemaker. This early-stage research marks the first time this has been achieved using a material other than living cells.

“This is a significant step towards developing a model of cardiac muscle that might one day be used to study the interplay of mechanical and chemical signals in the human heart,” Dr Hayashi said. “It opens up exciting possibilities for replacing some animal experiments in cardiac research with these chemically-powered gel models.”

The researchers found that by applying cyclic compressions to the gel, they could entrain its chemical oscillations to sync with the mechanical rhythm. Interestingly, the gel retained a memory of this entrained beating even after the mechanical pacemaker was stopped.

Lead author of the study, Dr Tunde Geher-Herczegh, said the findings could provide new ways to investigate cardiac arrhythmia, a condition in which the heart beats too fast, too slow or irregularly, which affects more than 2 million people in the UK.

She said: “An irregular heart beat can be managed with drugs or an electrical pacemaker, but the complexity of biological heart cells makes it difficult to study the underlying mechanical systems, independently from the chemical and electrical systems in the heart.

“Our findings could lead to new discoveries and potential treatments for arrythmia, and will contribute to our understanding of how artificial materials could be used in place of animals and biological tissues, for research and treatments in the future.”

The future of adaptive hydrogels

By developing alternative lab models for advancing cardiac research, these hydrogel materials also hold the potential to reduce the use of animals in medical studies, offering a potentially more ethical and efficient approach to understanding and treating heart conditions. Hayashi explained the underlying principle in a press release: “The basic principle in both neurons and hydrogels is that ion migration and distributions can work as a memory function which can correlate with sensory-motor loops in the Pong world. In neurons, ions run within the cells. In the gel, they run outside.”