CEO hopes to cool Japan with electricity-free material

In a recent interview with Jiji Press, Tiffany Yeh, 30, co-founder and CEO of San Francisco-based startup Eztia, said her aspiration is to deliver the material all over the world, including developing countries.

The company has developed proprietary cooling material HydraVolt, a special polymer gel that retains moisture and can lower skin temperature by up to 10 degrees Celsius through evaporative cooling.

The material can be sewn onto shirts, arm sleeves and other garments in dot-like patches. The cooling effect lasts up to eight hours and is restored when the material absorbs water during washing.

It is lightweight and flexible, making it suitable for workers who move around actively, said Yeh, one of Forbes magazine's 2025 "30 Under 30" honorees.

"Bringing energy-efficient cooling is important to both people and infrastructure, because it's about sustainability," she emphasized, citing growing energy demand due to climate change and the massive computing power required for artificial intelligence.

Since last year, Eztia has participated in an acceleration program offered by San Francisco-based venture capital Scrum Ventures LLC in the northernmost prefecture of Hokkaido.

It has conducted demonstration tests for its cooling products with a local elementary school basketball club, parcel delivery group Yamato Holdings Co. and the Hokkaido Nippon-Ham Fighters professional baseball team.

Eztia tested a cooling bandana-type product for heatstroke prevention with schoolchildren, an arm cover with Yamato delivery drivers to reduce heat stress, and headbands and other products with Nippon-Ham players and coaches to support heat management and improve athletic performance.

"We are really committed to Japan for the long haul because we see a lot of different types of positive impact we can create," she said, indicating interest in conducting a survey to explore the possibility of providing the technology to elderly people as well.

Originally from Taiwan, Yeh moved to the United States after graduating from high school and studied materials science at the Massachusetts Institute of Technology. She later earned a medical degree from the University of Pennsylvania.

Rather than pursuing a medical residency, however, she co-founded the company in 2022, after visits to developing countries for global health work and development projects changed her thinking.

"I would live out of a backpack, or suitcases, across different countries in Africa and Asia, and there was definitely no air conditioning. Sometimes we had no electricity or running water," she recalled.

"So it was a very specific problem but at least one that I personally experienced and thought about; which is, how do I stay cold in an environment where I have very little infrastructure for support?"

In medical school, she read many research papers on cooling materials and considered whether they could be applied to cooling people. After graduation, she rented a lab space and started mixing chemicals to create such a material.

"I have always been fascinated by the potential of technology to impact the masses, and how you implement and scale technology to affect a lot of people," she said.

Yeh hopes to deliver the material to developing countries, but she will first aim to spread its products to Japanese businesses.

She said: "As we grow, we get to serve broader populations. That is kind of a longer-term aspiration for us."