Scientists develop wearable sensors to monitor blood sugar from sweat

Scientists have developed a new sponge-like copper-based material for wearable sensors that can measure blood sugar levels from sweat, an advance that may allow diabetics to painlessly monitor their disease.

People with diabetes often have low levels of insulin, a hormone that converts sugars to energy, which means they have to closely watch their glucose or blood-sugar levels to prevent further chronic health complications.

Researchers at the University of Wollongong's (UOW) in Australia have demonstrated the first reported construction of copper with a sponge-like porous structure, which can also quickly and accurately detect glucose in body fluids other than blood, such as sweat or tears.

Professor Yusuke Yamauchi, from Japan's National Institute of Materials Science, said glucose sensors based on copper have been intensively studied, owing to the material's good conductivity, low cost and superior performance.

Copper is hard to fabricate into porous structures because it easily oxidises when exposed to air which highly affects its performance.

"Not only are these metals are highly reactive with air, they do not reduce easily in solutions and are difficult to deposit consistently on to substrates," he said.

Researchers mixed a liquid solution of copper and polystyrene, creating small
polystyrene balls with copper attached to the outside.

These can be attached to a substrate using a method similar to electroplating, and a UV light melts the polystyrene centres, leaving tiny holes each roughly 10,000 times smaller than the thickness of a human hair.

The result is a porous copper film with the sponge-like structure. Further testing showed the film has high selectivity, reacting to glucose without interference from other acids and sugars that can be present in sweat.

A key requirement for materials to be suitable for use as a sensor is high sensitivity, rapidly reacting to the presence of glucose in small amounts of liquid that also tend to evaporate quickly.

"The sponge-like porous structure greatly increases the surface area and therefore enhances the sensitivity required to trigger an electrochemical signal," Yamauchi said.

"The extraordinary sensing performance of the copper film is probably attributed to its intrinsically good reaction toward glucose oxidation," he said.

"This makes this copper film a good candidate for the direct detection of glucose to satisfy the requirements of diverse applications, such as diabetes management," he added.

The copper film may be integrated into a wearable sensor or a smartwatch, providing continual glucose readings to the wearer, which could also be sent wirelessly to their doctor.

The cheap materials also make it ideal for use in remote areas where access to clinics and health specialists is difficult.

The results were published in the journal Angewandte Chemie.