Scientists Create a ‘Breathable’ Hydrogel Inspired by Human Lungs

Wearable health sensors capable of continuously monitoring changes in the body have become a massive development in health technology in recent years.

These devices, along with medical patches and wound dressings, often need to remain in contact with the skin for hours or days. However, the water-rich hydrogels commonly used in such products can trap heat and sweat, potentially causing irritation and disrupting sensor readings.

In a new study published in Nature, engineers led by a team at the Massachusetts Institute of Technology (MIT) report developing a hydrogel containing a stable, three-dimensional network of microscopic, air-filled channels.

A 2024 study published in Science Advances achieved eight days of continuous skin monitoring using a gas-permeable hydrogel sensor about 10 micrometers thick and reinforced with a polyurethane nanomesh.

The new MIT study takes a different approach, creating a stable network of air pathways within a bulk hydrogel while maintaining a water content of 70 percent.

Despite being 70 percent water, the material achieved an oxygen permeability of up to 185 barrer (that’s not a typo, that’s the unit of measurement for gas permeability!) in laboratory tests.

That’s around 10 times more permeable than a conventional hydrogel.

Inspired by the air-carrying architecture of human lungs, the researchers took a regular hydrogel recipe and added a small amount of silica aerogel particles – essentially ‘solid-form’ air bubbles. These water-repelling particles trap air and prevent the tiny air spaces inside them from collapsing or filling with water.

During production, the particles came together inside the hydrogel to form a thin, interconnected network of air-filled channels. These channels allowed oxygen and water vapor to travel through the material while it retained its high water content.

The hydrogels also transmitted water vapor at rates 10 to 100 times higher than silicone and polyurethane patches, helping moisture escape from the skin.

The hydrogel was also soft and durable, retaining about 95 percent of its air permeability after 10,000 stretching cycles.

To prove the wearability of the new product, researchers tested the comfort of wearing their patches compared to more common silicone ones.

Infrared images taken two minutes after the patches were removed showed that skin temperature beneath a commercial silicone patch had risen by 6.5 degrees Celsius following a 20-minute workout.

Beneath the new hydrogel, however, it had fallen by about 1 degree, possibly because the material allowed heat to escape more efficiently.

A substantial amount of sweat also collected under the silicone patch, while skin covered by the breathable hydrogel remained similar to uncovered skin.

In another test, 10 volunteers wore the new patches on their chests during an hour of moderate exercise, with none reporting itching, irritation, or other adverse skin reactions.

The team also adapted the hydrogel for use as an electrode that records the heart’s electrical activity.

During cycling tests, conventional hydrogel electrodes produced less stable electrocardiogram (ECG) signals as sweat accumulated. Electrodes made with the air-permeable hydrogel maintained clearer readings during and after exercise.

In extended monitoring, the hydrogel electrodes were worn continuously for 10 days and continued recording usable ECG signals during activities including sleeping, working, walking, and exercising.

Xuanhe Zhao, the study’s senior author and mechanical engineer at MIT, told ScienceAlert that the most immediate applications could include wearable medical devices, wound dressings, and skin-mounted health monitors.

“These technologies often require prolonged contact with the skin, but conventional hydrogels trap heat and moisture because they do not allow sufficient oxygen and water vapor to pass through,” Zhao said.

 “Our material overcomes this limitation while maintaining the high water content and softness that make hydrogels comfortable and biocompatible.”

However, the material is not yet ready for clinical use. Zhao says further studies will need to assess its long-term biocompatibility, performance on large animals, sterilization, manufacturing at scale, shelf life, and regulatory safety.

The human tests were small and designed mainly to demonstrate the material’s feasibility. 

The exercise and comfort assessments involved up to 10 volunteers, while the skin physiology measurements included only two participants and the exercise ECG comparison involved three. Larger and more diverse studies will therefore be needed to confirm the findings.

The material will also need to be adapted for individual products, as a wound dressing, wearable sensor, and implant each has different requirements.

The current material is not inherently adhesive, meaning it still requires a separate backing or attachment mechanism to remain on the skin.

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In the longer term, the design could potentially be used in tissue engineering and implantable devices, where keeping cells supplied with oxygen remains a major challenge.

“Many engineered tissues and implants require efficient oxygen transport to maintain cell viability, and our material offers a way to improve gas exchange while preserving the hydrated environment that cells need,” Zhao said.

However, implantable applications will require substantially more testing, he cautions, making skin-based uses the more realistic first step.

The findings are reported in Nature.