What if your shirt could prevent heat stroke?

When Tiffany Yeh ’17 was at MIT—and later in medical school—she spent a lot of time doing field work in hot places. She wasn’t comfortable.

“I overheat a lot when I don’t have air conditioning and refrigeration,” she says. So, she asked herself: “Can I make a cooling material that I can just throw in a suitcase?”

The answer, it turns out, was yes—and today Yeh is the CEO of Eztia, a company she cofounded in 2022 to market the proprietary, water-based polymer gel she developed for personal cooling. Incorporated into fabric and worn next to the skin, the gel can reduce skin temperature by 10°C (18°F) by absorbing body heat and dissipating it into the air.

“It’s like additional sweating capacity through a second skin,” Yeh says, noting that the gel will provide cooling for six to eight hours, after which a short soak in water recharges it for reuse.

Since even a slight rise in body temperature can increase the likelihood of heat-related death or illness, Yeh believes her product could be a lifesaver. “The end objective is to prevent heat-related illness by dissipating heat load,” she explains.

Health applications of technology have always been a passion for Yeh, who was named to the 2025 Forbes list of 30 innovators under 30 . Raised in Taiwan, she came to MIT expecting she would eventually become a practicing physician. She majored in materials science for the sheer joy of it. “My mindset was: What was the most fun thing I could possibly do that doesn’t have to be justified by a career?” she says. “I find materials so fascinating. They comprise the tangible environment, the things we use to live.”

Yeh completed her premed requirements at MIT, but she also did a lot of experiential learning abroad—including in Zambia, India, and Sri Lanka—with support from D-Lab, the Priscilla King Gray Public Service Center, and the MIT Global Startup Labs.

Then, after a year working at pharmaceutical company Novartis, Yeh went to medical school at the University of Pennsylvania. She was pursuing her interest in global health when the Covid pandemic struck in 2020 and upended her plans to resume research into cancer treatment outcomes in Rwanda. Instead, she found herself spending a lot of time in one hospital, fulfilling her clinical rotation in surgery.

That experience made her take a long, hard look at her chosen career path. “To be honest, I kind of got cold feet,” she says. Realizing she didn’t want to work in an operating room “every day for the next 40 years,” Yeh decided not to pursue a medical residency after earning her MD. Instead, she sought out the variety, global travel, and endless problem-solving of entrepreneurship.

She began with a passion project she’d begun during medical school to solve her problem of overheating while traveling. After diving into the research literature, she says, “I became obsessed with using polymers for human cooling.” She tried a variety of off-the-shelf materials, then went into the lab herself to develop Eztia’s core material.

To help her turn her invention into a business, she then teamed up with Jack Wilson, a firefighter and military veteran with an MBA from New York University. Their approach at Eztia is to target industries, such as construction and the military, where people frequently work in the heat.

Soon the company had found its first customers— Muller Construction Supply in the United States and Kajima Construction in Japan. This year, Eztia also launched a pilot to provide Singapore with cooling materials for its police force.

Selling to large enterprises makes the most business sense for Eztia at this point, Yeh says, but she hopes to provide products to the average consumer in the future. “One day we’d love to partner with an apparel brand and get hydrogel on clothes for athletes, weekend warriors, and more,” she says. “That’s the core of our venture: We work on materials that impact people’s daily lives.”