Solar device can sterilize medical tools in off-grid areas without the need for electricity

 Solar device can sterilize medical tools in off-grid areas without the need for electricity

 

Autoclaves, the devices used to sterilize medical tools in hospitals, clinics, and doctors' and dentists' offices, require a steady supply of pressurized steam at a temperature of about 125 degrees Celsius. This is usually provided by electrical or fuel-powered boilers, but in many rural areas, especially in the developing world, power can be unreliable or unavailable, and fuel is expensive.

Now, a team of researchers at MIT and the Indian Institute of Technology has come up with a way to generate the needed steam passively, using just the power of sunlight, with no need for fuel or electricity. The device, which would require a solar collector of about 2 square meters (or yards) to power a typical small-clinic autoclave, could maintain safe, sterile equipment at low cost in remote locations. A prototype was successfully tested in Mumbai, India.

The system is described in the journal Joule, in a paper by MIT graduate student Lin Zhao, MIT Professor Evelyn Wang, MIT Professor Gang Chen, and 10 others at MIT and IIT Bombay.

The key to the new system is the use of optically transparent aerogel, a material developed over the last few years by Wang and her collaborators. The material is essentially a lightweight foam made of silica, the material of beach sand, and consists mostly of air. Light as it is, the material provides effective thermal insulation, reducing the rate of heat loss by tenfold.

This transparent insulating material is bonded onto the top of what is essentially off-the-shelf equipment for producing solar hot water, which consists of a copper plate with a heat-absorbing black coating, bonded to a set of pipes on the underside. As the sun heats the plate, water flowing through the pipes underneath picks up that heat. But with the addition of the transparent insulating layer on top, plus polished aluminum mirrors on each side of the plate to direct extra sunlight at the plate, the system can generate high-temperature steam instead of just hot water. The system uses gravity to feed water from a tank into the plate; the steam then rises to the top of the enclosure and is fed out through another pipe, which carries the pressurized steam to the autoclave. A steady supply of steam must be maintained for 30 minutes to achieve proper sterilization.

Since a large part of the creating scene faces restricted accessibility of solid power or moderate fuel, "we considered this to be an occasion to consider how we can conceivably make a minimal effort, inactive, sunlight based driven framework to produce steam, at the conditions that are fundamental for autoclaving or for clinical sanitization," clarifies Wang, who is the Gail E. Kendall Professor of Mechanical Engineering and top of the mechanical designing office.

Having the option to test the framework in Mumbai was a reward, she says, as a result of the city's "pertinence and significance" as the kind of area that may profit by such ease steam-age gear.

In the Mumbai tests, despite the fact that the sky was dim and shady, giving just 70% insolation contrasted with a radiant day, the gadget prevailing with regards to creating the immersed steam required for cleansing for the necessary half hour time frame.

The test was completed with a little scope unit, just about a fourth of a square meter, about the size of a hand towel, however it demonstrated that the steam creation rate was adequate that a comparative unit of somewhere close to 1 and 3 square meters would be adequate to control a benchtop autoclave of the sort regularly utilized in a specialist's office, Zhao says.

The primary restricting element for handy organization of such gadgets is the accessibility of the aerogel material. One organization, established by Elise Strobach Ph.D. '20, who is a co-writer of this paper, is now endeavoring to scale up the creation of straightforward aerogel, for use in high warm effectiveness windows. However, so far the material is just delivered in limited quantities utilizing moderately costly lab grade supercritical drying gear, so far and wide reception of such a cleansing framework is likely still a couple of years off, the scientists state.

The video shows the field test arrangement in Mumbai, India, and how steam was created persistently during tests. Credit: Lin Zhao

Since different segments, aside from the aerogel itself, are now generally accessible with ease all through the creating scene, manufacture and upkeep of such frameworks may eventually be handy in the zones where they would be utilized. The parts required for the quarter-square-meter model came to under $40, Zhao says, so a framework adequate for a commonplace little autoclave would probably cost $160 or somewhere in the vicinity, when the fundamental aerogel material gets marketed. "In the event that we can get the gracefully of aerogel, the entire thing can be assembled locally, with nearby providers," he says.

The cycle could likewise be utilized for an assortment of different purposes, the group says. For instance, numerous food and refreshment preparing frameworks depend on high-temperature steam, which is regularly given by petroleum product fueled boilers. Aloof sunlight based controlled frameworks to convey that steam would wipe out the fuel costs, thus could be an alluring choice in numerous businesses, they state.

Eventually, such frameworks should be significantly more savvy than frameworks that concentrate daylight by ten times or more to produce steam, on the grounds that those require costly mirrors and mountings, instead of the effortlessness of this aerogel-based methodology.

"This is a critical development," says Ravi Prasher, an educator of mechanical designing at the University of California at Berkeley and a partner chief at Lawrence Berkeley National Laboratory, who was not associated with this work. "Creating high-temperature steam with high energy productivity has been a test. Here the creators have accomplished both."

"The nature of the examination is high," Prasher adds. "Admittance to aloof sanitization methods for low-pay networks who don't approach solid power is serious. Subsequently, the aloof sun oriented gadget created by the MIT group is critical in such manner."

Journal information: Joule