Researchers in Brazil have developed a wearable sweat sensor made from microbial nanocellulose. The natural polymer provides a breathable interface with the underlying skin and allows sweat to travel through for electrochemical analysis using printed electrodes. The system can measure a wide variety of metabolites and biomarkers present in sweat, and could be useful for monitoring conditions such as diabetes. Wearable sensors are developing apace, and hold significant promise in monitoring various biomarkers. However, developing materials that interface well with the skin is a challenge, with many sensors, including plastic-based films, causing sweat to build up underneath, hindering measurements and causing irritation. These researchers set out to develop a sensor that would allow the underlying skin to breathe, and used a natural polymer to achieve this. “Microbial nanocellulose is a 100% natural polymer. It is produced by bacteria from sugar. Its main advantage over plastic is its far better interface with human skin,” said Robson Rosa da Silva, a researcher involved in the study. “It’s been commercially available for some years for use in wound dressings, among other applications, but it had never before been studied as an electrochemical sensor substrate. Nanocellulose is totally breathable, enabling sweat to reach the electrode’s active layer.” The new sensors are very small, at only 1.5 cm in length. The electrodes are printed onto the nanocellulose membrane, and contain a high proportion of carbon. “Chemical oxidation-reduction reactions produce an electrical signal that measures the concentration of the metabolite of interest,” said Paulo Augusto Raymundo Pereira, another researcher involved in the study. “The sensor is connected to a potentiostat that makes electrochemical measurements by means of variations in the electric current. The data obtained are transmitted to a computer and converted into standard curves.” A range of biomarkers are measurable by the device, including glucose, lactic acid, potassium, and sodium. “These elements or substances circulate in the bloodstream and are also detectable in sweat. Therefore, diabetes monitoring is one possible application of the nanocellulose sensor. Another is hormone control in women via detection of the hormone estradiol,” said Silva. Source
