Pill-sized chemical heater for point-of-care diagnostic tests

The researchers observed that the reproducibility of the temperature profile is controlled by constant gas release, which is dictated by the shape of the lithium mould.

Researchers at the University of Toronto have developed a ‘heater’ — about the size of a pill tablet — that regulates the temperature of biological samples through the different stages of diagnostic testing. This technology could enable resource-limited regions around the world to test for infectious diseases without the need for specialised training or costly lab equipment.

“The lack of electricity adds a layer of complexity,” said Buddhisha Udugama, a researcher involved in the study. “Our miniature heater addresses that. It can be used in various settings to detect viruses without the need for electricity. If we were to summarise the benefits of our technology, it would be accessibility, portability and precision.”

Udugama adds, “The precision and flexibility of our heater opens the door to a future of do-it-yourself diagnostic kits.”

In a typical diagnostic test for infectious pathogens, multiple temperature-regulation steps are involved. The ability to control temperature is crucial to the accuracy of the test results, and is especially important in areas where access to large research facilities are limited.

The outside of the heater tablet is composed of a non-reactive acrylic mould that encapsulates lithium, a reactive element that is commonly found in battery cells. When dissolved in water, the reactive lithium interacts with the solution to release heat and hydrogen gas. This results in an increase of temperature for an extended period of time.

The researchers observed that the reproducibility of the temperature profile is controlled by constant gas release, which is dictated by the shape of the lithium mould. After testing multiple shapes of the lithium mould – from circles to triangles – they found the star shape, measuring just 8 millimetres in diameter, to be the most ideal for precise heating.

Consolidating multiple steps into a single tablet also means specialised training is not required to operate any diagnostic testing, reducing the chance of human error and making the device accessible to the public.

“Tablets are conventionally used for medications such as aspirins. But we have now developed a series of tablets and pills that can diagnose diseases,” said Warren Chan, principal investigator on this research and director of IBBME. “Combined with smartphone technology, everyone would have a portable system that can track, monitor and diagnose infections. This is critical for preventing the spread of diseases.”