When Professor Emeritus of Physics Derek Stein was seeking research funding to help buildings manage moisture, one program manager told him the idea sounded like magic. Stein was ultimately told it wouldn’t work, and that even if it did, no one would care.
Now, Lilypad, the paint and primer system developed by Stein’s company Adept Materials, has been named one of TIME’s best inventions of 2026.
Lilypad is a two-layer paint and primer system designed to absorb excess water vapor in the air when indoor humidity rises and release vapor when humidity falls. The system is meant to protect buildings from deterioration caused by water damage.
For Stein, the journey towards creating Lilypad involved much more than the invention of a new material — it involved learning how to build a company as well as leaving his professorship.
The idea for the product emerged from a Brown student project. Around 2012, engineering students approached Stein for help with an international challenge to design and build a sustainable house. As they strove to build an energy-efficient home, Stein noticed a tension emerging: While energy-efficient buildings are well insulated to reduce air-conditioning and heating costs, these same properties have the unintended side effect of trapping moisture as well.
“So the very same buildings that are getting more efficient can actually get less comfortable, less durable and less healthy,” Stein said.
Stein turned to plants for inspiration. Unlike houses, plants respond to changing conditions while regulating their own moisture.
Initially, Stein pursued potential solutions for the issue through familiar academic channels by applying for grants to support his research. While these applications did not ultimately pan out, individuals in other sectors — such as the construction industry — expressed interest.
Danny Warshay ’87 P’20 P’23.5, executive director of the Nelson Center for Entrepreneurship, encouraged Stein to consider creating a startup for the product while remaining a full-time faculty member.
“I think my role can be best described as a cheerleader,” Warshay said. “I was trying to encourage him, mostly to help him understand that he could do what he was envisioning … that he could, even while being a professor, pursue starting a venture.”
Brian Demers ’85, senior director of business development at Brown Technology Innovations, helped Stein identify which discoveries could be patented and connected him with investors and other industry contacts.
“(Stein is) great at being able to talk to and present to different audiences and get them to understand what he’s up to,” Demers said.
Jason Harry, professor of the practice of technology and entrepreneurship, helped review Stein’s early pitch presentations. Paint was not the focus of the first presentations, he said, as Stein was exploring many other materials that could potentially incorporate the technology.
For solutions with multiple possible approaches, finding the right first application is a central challenge, Harry explained. “It’s where the unmet need is the most acute.”
With the support and advice from his colleagues, Stein took additional steps towards turning his technology into a product. He enrolled in the Cleantech Open accelerator, an entrepreneurship training program, to learn the basics of entrepreneurship.
Stein retired from his professorship in 2024 to focus on Adept Materials. Despite his departure from academia, he compared his experience launching Lilypad to how he used to feel when publishing research papers.
“I was super nervous when (Lilypad) came out,” Stein said. “You’re doing all this work, and you don’t want it to all fall apart.”
But early positive feedback offered reassurance. Stein recalled hearing assessments from a professional painter who praised the paint’s artistic value as well as from customers who said their bathroom stayed dry after a hot shower. These accounts, he said, were especially rewarding because these people had no reason to praise him.
“This isn’t my mom telling me, ‘I really like your thing,’” he said.
The recognition has since grown — Adept Materials won Startup of the Year at the 2025 Innovations@Brown showcase, and Lilypad received a Fast Company Innovation by Design award in September.
Stein is already thinking about going beyond interior walls and expanding the product line. Lilypad recently added colors beyond their initial release, which only offered white, he said. Adept Materials is also exploring the potential to produce exterior paint, food packaging and clothing apparel regulated for humidity, Stein said.
