1.7.2020 11:04 PM

Innovation

It's time to wear your air conditioner, scientists say

A team at the University of Missouri may have the answer.

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Now here’s a cool idea: a wearable air conditioning system that could help reduce body temperatures without using extra electricity.

Researchers at the University of Missouri announced Monday they have developed an on-skin device that can keep users cool through the use of a technique called “passive cooling.” It uses a patch that’s breathable, waterproof, and doesn’t use any fans or pumps. The cooling forms part of a wearable sensor system, which can collect information about vital signs like blood pressure similar to an Apple Watch. The results were published in the journal PNAS.

“We believe this is one of the first demonstrations of this capability in the emerging field of on-skin electronics,” author Zheng Yan, an assistant professor in the College of Engineering, said in a statement.

Air conditioning is a major concern as countries fight to reduce carbon emissions. The International Energy Agency claims that, as the rest of the world starts to use as many air conditioners as the United States, it could account for around 13 percent of global electricity usage and produce as many emissions as India, the third-biggest emitter. The International Renewable Energy Agency warned in April 2019 that the world is not on track to switch to renewables, a key factor that could mitigate this rise.

With breakthroughs like these, cooler heads could prevail.

Wearable air conditioning in action.University of Missouri

The University of Missouri’s design uses passive cooling to reduce body temperatures. This is similar to techniques used in building design, which can use materials to dissipate heat.

The team’s design has two functions. It can reflect sunlight, stopping it from ever reaching the skin. It can also allow the body to dissipate the heat. The end result is a human body that’s 11 degrees Fahrenheit cooler during daytime hours.

Beyond its cooling qualities, the device is equipped with a number of sensors that can monitor human health. This includes blood pressure, heart activity and skin hydration. The design could also support other wearable tech applications, like virtual reality interaction or human-computer interfacing.

Although the system is currently a wired device, the goal is to develop a wireless version over the next two years. The team would then aim to expand its size to cover full-scale “smart” clothes.

“Eventually, we would like to take this technology and apply it to the development of smart textiles,” Yan said. “That would allow for the device’s cooling capabilities to be delivered across the whole body. Right now, the cooling is only concentrated in a specific area where the patch is located. We believe this could potentially help reduce electricity usage and also help with global warming.”

As air conditioning threatens to wreck the progress toward reducing carbon emissions, it could be a much-needed breakthrough.

Read the abstract below:

In addition to mechanical compliance, achieving the full potential of on-skin electronics needs the introduction of other features. For example, substantial progress has been achieved in creating biodegradable, self-healing, or breathable, on-skin electronics. However, the research of making on-skin electronics with passive-cooling capabilities, which can reduce energy consumption and improve user comfort, is still rare. Herein, we report the development of multifunctional on-skin electronics, which can passively cool human bodies without needing any energy consumption. This property is inherited from multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) supporting substrates. The multiscale pores of SEBS substrates, with characteristic sizes ranging from around 0.2 to 7 µm, can effectively backscatter sunlight to minimize heat absorption but are too small to reflect human-body midinfrared radiation to retain heat dissipation, thereby delivering around 6 °C cooling effects under a solar intensity of 840 W⋅m−2. Other desired properties, rooted in multiscale porous SEBS substrates, include high breathability and outstanding waterproofing. The proof-of-concept bioelectronic devices include electrophysiological sensors, temperature sensors, hydration sensors, pressure sensors, and electrical stimulators, which are made via spray printing of silver nanowires on multiscale porous SEBS substrates. The devices show comparable electrical performances with conventional, rigid, nonporous ones. Also, their applications in cuffless blood pressure measurement, interactive virtual reality, and human–machine interface are demonstrated. Notably, the enabled on-skin devices are dissolvable in several organic solvents and can be recycled to reduce electronic waste and manufacturing cost. Such on-skin electronics can serve as the basis for future multifunctional smart textiles with passive-cooling functionalities.
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