by Abby McBride
October 14, 2011
With a bucket, a pressure cooker, and 140 pocket-sized mirrors, MIT-affiliated researchers have invented a device that uses sunshine to sterilize surgical tools.
They are field-testing the device in Nicaragua as part of a broad plan to help people in developing countries cope with severely limited medical resources.
Most of Nicaragua’s 1,500 rural clinics lack the electricity to power an autoclave, which is a high-pressure chamber for sterilizing tools. Nurses resort to measures such as trekking to a regional health center over the weekend to sterilize a batch of instruments. They are often forced to either use unsterilized instruments or turn people away.
Ted Liao and Anna Young tackled this problem as part of MIT’sInnovations in International Health program (IIH). In July 2011 they developed a prototype of their solar autoclave, dubbed “Solarclave,” and over the summer they collaborated with rural Nicaraguans to hone the design.
Solarclave has a reflector that focuses sunlight onto a vessel containing the surgical instruments. Light rays heat the vessel to over 300° F, surpassing the 250° degree minimum needed to sterilize the instruments inside.
The vessel is simply a modified pressure cooker purchased from a local Nicaraguan market, says lead engineer Liao, a medical student at Boston University. The cooker is wrapped in fiberglass insulation and built into an upside-down bucket, which is suspended a couple of feet above the ground.
On the ground below the vessel sits the reflector, a mosaic of small, ten-cent mirrors arranged at different angles on a plywood lattice. Light bounces off of each mirror and up into the bucket, striking and heating the presser cooker inside. The contents are sterilized within about an hour.
The Solarclave’s heavy insulation keeps the vessel hot even when the sun goes behind a cloud. “We did our local testing during the rainy season, and we were able to hit required temperatures at least once each day between batches of clouds,” wrote Liao in an email.
One Solarclave costs about $150 in local materials and consumes no fuel, making it a practical option for rural clinics. A kerosene-powered stovetop autoclave, on the other hand, would cost about $300 up front and use $4 worth of fuel per use.
To build the prototypes, IIH has worked with a Nicaraguan women’s manufacturing cooperative, Las Mujeres Solares. “We’ve shown that what we’ve designed can be built by this group, and it’s quite easy for them to do it,” says Liao.
IIH also field-tested the device with local doctors and nurses over the summer, continually tweaking the design to address logistical questions such as “where are they going to store it, how are they going to move it out, how are they going to set it up, how are they going to adjust it,” Liao explains.
After making a few more changes to the device based on the recent testing, IIH plans to transition into an advisory role. The organization hopes that local manufacturing groups will continue to build and sell Solarclaves on their own, making modifications as they see fit. “The idea is for this to be sustainable,” says Young, IIH’s Research and Development officer.
Solarclave is one of a suite of collaborative projects that IIH has initiated in Nicaragua and other developing countries. Other innovations include bike pump-powered nebulizers, diagnostic tests made of paper, and build-it-yourself kits that allow medical professionals to mix and match parts to create the equipment they need.
By emphasizing collaboration and inventiveness, IIH believes it is successfully empowering rural residents to take control of their own health care problems. The collaborative approach is “awesome,” agrees Lori McIlvaine, a founder of the nonprofit organization Salud del Sol, which helped fund the Solarclave project.
IIH director Jose Gomez-Marquez points out that the program does face obstacles such as funding and the challenge of sustaining local engagement in between field trips. It’s important to keep in touch with the community and press on, says Liao. “We try to keep the ball rolling all the time.”