A wearable device that can measure gases emitted from and absorbed by the skin has been developed by researchers at Northwestern University in Illinois.

By analysing these gases, the device can assess skin health, including monitoring wounds, detecting skin infections, tracking hydration levels and quantifying exposure to harmful environmental chemicals.

The technology comprises a collection of sensors that precisely measure changes in temperature, water vapour, carbon dioxide (CO₂) and volatile organic compounds (VOCs), which each give insight into various skin conditions and overall health. These gases flow into a small chamber within the device that hovers above the skin without actually touching it. This no-contact design is useful for gathering information about fragile skin without disturbing delicate tissues.

The study was published this month in the journal Nature, www.nature.com/articles/s41586-025-08825-2.

“This device is a natural evolution of our lab’s wearable electronic devices that collect and analyse sweat,” said Northwestern’s John Rogers, who co-led the study. “In that case, we were analysing sweat to learn about the wearer’s overall health. While useful, that method requires pharmacological stimulation of sweat glands or exposure to a hot, humid environment. We started thinking about what we could capture from the skin that is naturally occurring all the time. It turns out there are all kinds of things coming off the surface of the skin – water vapour, carbon dioxide and volatile organic compounds – that can be correlated to underlying physiological health.”

This technology has the potential to transform clinical care, particularly for vulnerable populations, including newborn babies, the elderly, patients with diabetes and others with compromised skin.

The outermost layer of skin maintains hydration by preventing excessive water loss and acts as a barrier against irritants, bacteria and ultraviolet radiation. When the skin barrier is compromised, it can lead to increased water loss, skin sensitivity, and risk of infection and inflammatory conditions such as eczema and psoriasis.

By tracking changes in the emission of water vapour and gases from the skin, healthcare professionals can gain a glimpse into the integrity of their patients’ skin barriers. While technologies to measure water vapour loss do exist, they are large, cumbersome machines that largely reside within hospital settings. This compact wearable device, on the other hand, is designed to help physicians monitor their patients remotely and to empower individuals to take control of their own skin health at home.

Measuring 2cm long and 1.5cm wide, the device comprises a chamber, sensors, programmable valve, electronic circuit and small rechargeable battery. Instead of touching the skin directly, the chamber hovers a few millimetres above it.

“Traditional wearable sensors rely on physical contact with the skin, limiting their use in sensitive situations, such as wound care or for individuals with fragile skin,” Rogers said. “Our device overcomes this limitation by creating a small, enclosed chamber above the skin’s surface.”

An automatic valve opens and closes the entrance to this chamber, a function that dynamically controls access between the enclosed chamber and the surrounding ambient air. When the valve is open, gases flow in or out of the chamber, enabling the device to establish a baseline measurement. Then, when the valve rapidly closes, it traps gases within the chamber. From there, the series of sensors measure changes in gas concentrations over time.

“If our device didn’t incorporate a programmable valve and a time-dynamic measurement approach to quantify flux of species out of and into the skin in a real-time manner, then the system could be confounded by changes in the concentrations of these species that might naturally vary in the surrounding environment,” Rogers said. “Specifically, if the valve were open all the time, the sensor would detect these sorts of changes, not because of anything associated with the skin. On the other hand, if the valve were always closed, then it would perturb natural patterns of flux in a way that also could not account for environmental factors. For workers in potentially hazardous environments, it’s helpful to know how much of those hazardous species are entering the body through the skin.”

Using Bluetooth, the device sends these data straight to a smartphone or tablet for real-time monitoring. These fast results can help healthcare workers make more informed and speedier decisions for wound management and for administering antibiotics.

Because increased water vapour, CO₂ and VOCs are associated with bacterial growth and delayed healing, monitoring these factors can help caregivers detect infections earlier and with more confidence.

The technology not only offers insights into wound healing and skin health, it also might pave the way for advances in monitoring the efficacy of bug repellents, skin creams and systemic medications designed to improve skin health.

CO₂ and VOCs are the very gases that attract mosquitos and other pests. So, measuring these emissions from the skin could help researchers understand and potentially mitigate mosquito attraction. The device also could let dermatologists and their patients measure how fast lotions and creams penetrate the skin, which could provide insights into skin permeability and barrier function. These data also could help other researchers develop more effective transdermal drug delivery systems, monitor the effects of systemically delivered drugs for skin diseases, and evaluate the safety of cosmetics and personal care products.

Next, the team plans to refine the device’s capabilities, including adding a sensor to track changes in pH levels and developing gas sensors with increased chemical selectivity for early detection of organ dysfunction and other diseases.

“This unusual wearable platform provides a new way to think about and understand skin health,” Rogers said. “This technology is not just about measuring gases and corresponding characteristics of the skin, it’s about predicting overall health, preventing infection and disease, and creating a future where personalised care is driven by real-time, non-invasive, continuous health tracking through a new collection of parameters that complement those that can be captured with conventional wearables.”

For more on Northwestern University, visit www.northwestern.edu.