It uses a transparent, cloud-like aerogel coupled with a solar heater to generate steam that is hot enough and at high enough pressure to sterilise medical instruments even under hazy and partly cloudy weather.
The researchers believe it can be used to help alleviate infection-related healthcare burden and facilitate the adoption of solar energy as a potential power source in resource-limited regions.
Devices called autoclaves, which use high temperatures and high pressure to sterilise medical equipment, are commonly used by medical professionals.
However, due to the heat loss to the environment, traditional solar heaters have difficulties reaching temperatures above boiling point. In the new study, the research team incorporated a thermal insulating aerogel into the solar thermal device to reduce the escaping heat, allowing the device to generate 128°C and 250kPa steam for sterilisation.
"When we were doing the field research in India, many healthcare providers said that they can operate an autoclave if there is reliable energy, but there are certain occasions where the electricity is unavailable," said first author Lin Zhao who conducted a field study in Mumbai, India.
"They are then forced to use maybe unsterilised equipment, or they have to use some rudimentary method like boiling water to try to sterilise things. A solar-powered device, in that case, would certainly be helpful to them."
Unlike other steam-generating solar thermal devices, which rely on solar tracking that requires operators to concentrate sunlight, the team's device is stationary, more user friendly, and energy efficient.
In the field test, the aerogel-aided device generated steam at 100°C with more than two times higher energy efficiency than other solar thermal devices reported in the lab.
"As long as you have sunlight, you can use this device. It doesn't have to rely on well-built infrastructure. You can use it off-grid in remote areas," said Zhao. But like other solar-powered gadgets, it also has a limit – cloudy and rainy days. "It really depends on your location. If you're in a sunny area, our device may offer more benefits."
Zhao and his colleagues' device also has a lower price tag, and most of its components are commercially available in the solar water-heater industry. Compared to benchtop autoclaves on the market, which can cost up to $3,000 (£2,280), the researchers' device costs about $35 per unit. Three to six units of the prototype device can sufficiently power a benchtop autoclave, demonstrating its potential as an inexpensive and accessible approach to reduce infection in remote and developing regions. The next step for the research team is to manufacture the aerogel in high quantity and quality.
"The real 'secret sauce' or the enabling factor is the transparent aerogel. Once we have the aerogel scaled up, we can think about providing the device to people who need it, such as channels like NGOs and other organisations," said Zhao.
"We can also think about using the same technology for larger-scale applications. For example, food-processing plants and chemical plants, they use boilers steam generators too."
