Breaking the Wall of Non-Degradable Plastics

Breaking the Wall of Non-Degradable Plastics  

Global Call 2025 Finalist Interview: Engineering & Technology  

Takuzo Aida is one of five University Distinguished Professors at the University of Tokyo and serves as Group Director at RIKEN. He completed his Ph.D. at the University of Tokyo in 1984 and was appointed full professor at the same university in 1996. His important achievement is the discovery and development of supramolecular polymers. He is an elected member of the Royal Netherlands Academy of Arts and Sciences (2020), the U.S. National Academy of Engineering (2021) and the American Academy of Arts and Sciences (2023). Aida continues to redefine the frontiers of polymer science. 

Which wall does your research or project break? 

Breaking the Wall of Non-Degradable Plastics: 

Plastics are originally designed to be durable and resistant to natural degradation in the environment. As a result, plastic waste contributes to serious environmental issues—its incineration releases greenhouse gases that drive climate change, while its weathering generates microplastics that pose threats to human health. These problems are no longer theoretical; they have become an imminent and tangible crisis for humanity. Unless we fundamentally transform our way of life we may face irreversible changes to our planet. However, if plastics can be designed to be mechanically robust while being rapidly degradable in response to natural stimuli, we may be able to reclaim a brighter future for our planet. 

As a scientist, I took on this challenge and invented supramolecular plastics—a novel material that addresses the long-standing issue of non-degradable plastics. Specifically, supramolecular plastics are mechanically tough but can dissociate upon exposure to environmental salts into their small-molecule precursors, which can then be metabolised by microorganisms. Moreover, supramolecular plastics allow for selective closed-loop recycling even in the presence of conventional plastics. This is not merely an improvement of existing technologies but an unprecedented innovation that embodies a bold vision for what the next generation of plastics ought to be. What kind of future would you like to pass on to your children? Children cannot choose the environment in which they will live. That responsibility lies with us. 

What is the main goal of your research or project? 

Through my research, I hope to contribute to mitigating global warming and environmental destruction caused by plastic waste. The world around us today looks vastly different from the one I knew as a child. Back then, summer temperatures exceeding 30 °C felt unusually hot. But now, temperatures approaching 40 °C have become commonplace. These changes are not only transforming the foundations of agriculture, fisheries and other industries essential to our food supply, but are also causing an environmental disaster—ranging from massive floods to the melting of glaciers. 

While plastic waste is not the sole cause of environmental degradation, it is undeniably one of the major contributing factors. Many researchers have focused on improving existing plastics to address this problem. However, even poly(lactic acid) (PLA), a leading biodegradable material, degrades very slowly in natural environments and still generates microplastics. There is growing concern that once microplastics enter the bloodstream, they can cross the blood-brain barrier, accumulate in the brain, and potentially cause harm. The supramolecular plastics I have developed look and feel very similar to conventional plastics. In fact, if someone were to receive a sample of supramolecular plastic without any explanation, they would likely assume it was an ordinary plastic and use it as such. Bags made from supramolecular plastics can be used to carry vegetables and fruits just like conventional ones. But in reality, these materials are fundamentally different. When placed in saline water, they dissolve and disappear—because they dissociate into their small-molecule precursors. In a marine environment, these small molecules are fully metabolised by microorganisms, leaving no trace. The same process occurs when the material is buried in soil. Of course, if the surface of the material is protected with a thin coating, it remains usable even in saline water, as long as the coating remains intact. The high sensitivity to salts also allows for selective closed-loop recycling of supramolecular plastics even in the presence of conventional plastics. 

In this research, I dedicated myself to ensuring that supramolecular plastics would be "similar yet fundamentally different" from conventional plastics. If their appearance or usability had been clearly different, no one would adopt them. Moving forward, I aim to bring this innovation into practical use. If replacing part of the plastics in our society with supramolecular plastics can help prevent further deterioration of our planet’s environment, then as a researcher, I will consider it a deeply fulfilling achievement. 

What advice would you give to young scientists or students interested in pursuing a career in research, or to your younger self starting in science? 

When I entered the doctoral program in an engineering graduate school, I did not originally intend to pursue a career in academia. However, during my PhD research, I encountered an unexpected discovery. Driven by curiosity to understand the phenomenon, I reserved the instrument in our department and stayed late at night to conduct experiments. Around 4 a.m., I saw a spectrum appear on the monitor that revealed the reason behind the phenomenon. Then, as I reached out to remove the sample from the machine—as I always did—I realised I could not do it properly. I looked at my hands and noticed they were shaking. The reason, I discovered, was that I was deeply moved by the discovery. It was the first time in my life that I truly felt such emotion. At that moment, I realised I had the capacity to be moved—and that such joy was possible through research. It was then that I knew, without doubt, I wanted to continue as a researcher in academia. Had I not made that discovery, I might have taken an entirely different path. 

Research can be demanding. It challenges you in ways you may not expect. But through that process, it reveals abilities within you that you did not know existed or helps you develop new strengths you never thought you had. If research were easy, that kind of personal growth would not happen. I experienced this firsthand—and because of that, I chose to work at a university where I could share this joy through both research and education. Since then, I’ve worked with many students in my lab—students who chose to pursue research alongside me. Many of them went on to doctoral studies and experienced similar moments of discovery and growth. Today, they are making meaningful contributions to society. 

Research and education transcend borders, cultures and languages. Through science—a common language—we can share ideas and collaborate with people around the world. No matter where we come from, the passion to explore the unknown is universal. This global connection is one of the true powers of scientific research. I encourage young scientists and students to value their curiosity and follow their interests. Do not fear failure. Have the courage to face the unknown because the steps you take today may one day help change the world. 

What inspired you to be in the profession you are today? 

During my time in graduate school, I made a discovery that made my whole body tremble with excitement, in sharp contrast to my usual demeanour. I thought, if I can experience something this thrilling, I want to become a researcher in academia.   

What impact does your research or project have on society?  

Plastic waste is known to harm our natural environment and contribute to global warming. Our technology aims to address this by creating supramolecular plastics that resemble conventional oil-based plastics in appearance and texture but are fundamentally different in that they degrade in the environment without generating microplastics. 

What’s the most exciting moment you've experienced over the course of your research or project? 

The most exciting moment was when we saw that our supramolecular plastics, that we had already confirmed to be mechanically strong, indeed dissolved in saline water and disappeared.