UNIVERSITY PARK, Pa. — Just over 20 years ago, Ayusman Sen, the Verne M. Willaman Professor of Chemistry in the Eberly College of Science at Penn State, was getting antsy to find a new and exciting direction for his research. Sen and his then-graduate student, Walter Paxton, embarked on a project with a team of collaborators in the chemistry and physics departments. The paper describing the results of that research is widely acknowledged as the first publication in the burgeoning field of autonomous nanomotors.

The paper, titled “Catalytic Nanomotors: Autonomous Movement of Striped Nanorods,” was published in the Journal of the American Chemical Society in 2004. Twenty years later, nanomotors — unfathomably small particles that can move autonomously and, eventually, hopefully, do helpful things — still feel like a futuristic wonder. But researchers around the world are looking for ways to use them for drug delivery or to fight cancer and a myriad of other applications.

The field has grown to the point at which two separate international professional conferences held this summer celebrated the 20th anniversary of the publication of the paper. Sen was a keynote speaker at the Nanomotor International Conference held in Barcelona, Spain, and at the Global Virtual Conference on Chemical Nanomotors held in conjunction with the fall 2024 meeting of the American Chemical Society in Colorado.

“Looking back at the trajectory of my career, I tend to change the focus of my research every 10 years or so,” Sen said. “I am a catalysis person for sure. We worked on making polymers using catalysis, and we worked on converting natural gas into other useful chemicals using catalysis. I got bored and I said to my graduate student, Wally, ‘we should make something move.’”

At a meeting of Paxton’s graduate committee, Emeritus Professor Tom Mallouk, provided the something. He was making nanorods precisely constructed out of various metals that he thought would be ideal for their experiments. With just the right structured rods in just the right solution of hydrogen peroxide, the rods moved.

“It was challenging to get funding and to get the paper published because what we were doing was so new,” Sen said. “In fact, we actually got the mechanism wrong when we first submitted the paper, but of course the observations were correct and we decribed the correct mechanism in later publications.”

A documentary film about nanobots featuring Sen by filmmaker Robert Brown is scheduled to be release to the public this year. The film, “Nanobots: A Fantastic Voyage,” received the award for Best Documentary at the International Hollywood Short Film Festival and was presented in a special screening at the conference in Barcelona.

“The growth of this field over the last 20 years has been mindboggling,” Sen said. “The majority of the applications of the technology being explored are in the field of medicine. I am more interested in what we can learn about how living systems evolved by studying autonomous nanomotors. I’ve stuck in this field for 20 years now and I’m now even more excited about the field moving forward. It has truly been a fantastic voyage for me and my fellow motorists!”