IIT Backed Research Tests Sterilisation of Medical tools Using Sunlight

Researchers from MIT (Massachusetts Institute of Technology) and IIT Mumbai have successfully tested an autoclave powered by sunlight to sterilise medical tools.

A Portable autoclave

Image Courtesy: Indosurgicals

Autoclaves are devices used to sterilize medical tools doing so by utilising pressurized steam at a temperature of about 125 degrees Celsius. Usually provided by electrical or fuel-powered boilers, the steam supply obviously needs to be steady, to ensure best results. Which is where the need for dependable power comes in, especially in rural areas with unpredictable power supply, or where power from other sources like gensets can be too expensive.

The joint research team of the two institutes came up with a  way to generate the needed steam passively, using just solar power. The device, which would require a solar collector or panel 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.

  • The key to the new system is the use of optically transparent aero gel, a material developed over the last few years by the researchers. The material is essentially light weight foam made of silica, and consists mostly of air. It provides effective thermal insulation, reducing the rate of heat loss by tenfold.
  • This transparent insulating material is bonded onto the top of 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 and 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.

The researchers saw a great opportunity in the developing world for such a tool, that can provide low-cost, passive, solar-driven system to generate steam that meets the necessary conditions for an autoclave to effectively and safely sterilise equipment.

The system was tested in Mumbai because of the city’s “relevance and importance” as the type of location that might benefit from such low-cost steam-generation equipment. In the Mumbai tests, even though the sky was hazy and cloudy, providing only 70 percent insolation compared to a sunny day, the device succeeded in producing the saturated steam needed for sterilization for the required half hour period. The test was carried out with a small-scale unit, only about a quarter of a square meter, about the size of a hand towel, but it showed that the steam production rate was sufficient that a similar unit of somewhere between 1 and 3 square meters would be sufficient to power a bench-top autoclave of the kind typically used in a larger medical unit or office.

The main limiting factor for practical deployment of such devices is the availability of the aerogel material. One company, founded by the team is already attempting to scale up the production of transparent aerogel, for use in high thermal efficiency windows. But sourcing the drying equipment to handle larger volumes  at scale means the actual go to market for the innovation is still some time off.

With typical Autoclaves starting at Rs 5,000 and going up all the way to Rs 25,000 and much more for larger uses, the estimated price of Rs 12,000 for this particular innovation is not too distant, provided the issue of aerosol gel is cracked.

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