Researchers at the University of Toronto have developed a miniaturized chemical heater that can precisely heat biological samples during diagnostic tests, but does not require electricity or any specialized equipment to work. The low-cost technology is based on the exothermic reaction that occurs when lithium encounters water, and the precise shape of the pill-sized heater dictates the heating profile it can produce.
Performing diagnostic assays to detect infectious diseases can be difficult in remote and low-income areas. Frequently, such assays require expensive and bulky lab equipment, and low-resource regions may not have a reliable source of electricity. However, sending samples to distant labs is often not practical or affordable, and when it comes to infectious diseases, it is important to get a result quickly.
One of the issues is that diagnostic tests require samples and reagents to be heated to specific temperatures at different points during such assays. In a lab, this is achieved using electrical heating equipment, such as incubators, water baths, or hot plates. To provide an alternative that can be used in the field, these researchers have created a miniaturized chemical heater.
“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 summarize the benefits of our technology, it would be accessibility, portability and precision.”
The heater consists of a lithium “pill” coated in a non-reactive substance. The small device can be added to a biological sample and will provide a specific amount of heat, achieved by the exothermic reaction that occurs when lithium reacts with water. By experimenting with the shape of the lithium mold, the researchers found that they could alter the heating profile and duration. They discovered that a star shape of 8 mm in diameter is best for precise heating.
The technology does not require any special skills or training, and reduces the potential for human error during assay performance. “Combined with smartphone technology, everyone would have a portable system that can track, monitor and diagnose infections,” said Warren Chan, another researcher involved in the study. “This is critical for preventing the spread of diseases.”
Study in PNAS: Tunable and precise miniature lithium heater for point-of-care applications