Hydrogel with micropillars keeps glass clear even in extreme condensation

"We wanted to try a different approach and create durable antifogging materials that could passively function in all environments," said co-principal investigator Thomas Schutzius, an associate professor of mechanical engineering at UC Berkeley who previously worked at ETH Zurich.

A coating that both loves and wicks water

The team's answer combines the two philosophies. "We wound up developing a coating that is both water loving and water wicking," Schutzius said.

The hydrogel is intrinsically hydrophilic because it is packed with nano-sized pores that soak up water. But that absorption capacity is finite: once the material saturates, droplets begin to form again. The researchers solved this by engineering the forest of cylindrical micropillars across the surface. The texture produces a microwicking effect — it draws water across the surface, generating a stable, continuous film that sustains transparency even under severe condensation.

"By changing the texture of the hydrogel so that fog droplets form a stable, continuous film, our solution can sustain surface transparency even under severe condensation conditions," Schutzius said.

How the researchers tested it

The team validated the micropatterned hydrogel across a range of condensation conditions. On both optical clarity and stability, it consistently outperformed competing antifogging alternatives, including superhydrophilic and superhydrophobic coatings.

Then came a practical, deliberately extreme test: cooking. The researchers placed a patch of the hydrogel on the underside of a glass pot lid and boiled zucchini and carrots beneath it. At first the patch looked misty, and the vegetables were hard to see. Within 30 seconds, it turned completely transparent again.

"We've shown that this micropatterned hydrogel is a practical solution for even the most demanding applications," Schutzius said. "Its unique combination of wet-state transparency, strong adhesion and reliable performance under severe condensation gives it a distinct advantage over existing antifogging technologies."

What comes next?

The findings come from laboratory conditions, and commercial deployment remains a question of industrial interest. Schutzius sees potential applications wherever optical transparency must survive heavy condensation — notably vehicles, where fog can temporarily obscure cameras and LiDAR sensors (light-based ranging devices used in driver-assistance systems), creating a safety issue.

"As we engage with industry, we'll see if there's interest in further developing this technology for other, specific applications," he said. "This could include sensors that operate outside the human visible spectrum or possibly applications that we haven't even thought of."

Schutzius co-led the investigation with Dimos Poulikakos of ETH Zurich. Co-authors include Hyunchul Park of ETH Zurich and the Korea Institute of Science and Technology; Cheuk Wing Edmond Lam of ETH Zurich and MIT; and Iwan Haechler of ETH Zurich and Solabs Nanotechnology GmbH.

Thirty seconds from mist to clear glass — a small patch that may keep tomorrow's sensors seeing straight.