Researchers develop wearable sensor to detect heavy metals in sweat

Heavy metals such as lead and cadmium are present in batteries, cosmetics, food and other things that are part of everyday life. They are toxic when they accumulate in the human organism, potentially causing numerous health problems, but detecting them in body fluids requires expensive equipment and a controlled laboratory environment. Researchers at the University of São Paulo (USP) in Brazil have now developed a portable sensor made of simple materials to detect heavy metals in sweat that can be easily sampled.

The research was supported by FAPESP (projects 16/01919-6 and 16/06612-6) and involved groups at the São Carlos Institutes of Physics (IFSC) and Chemistry (IQSC), as well as collaborators at the University of Munich in Germany and Chalmers Tekniska Högskola in Sweden.

The results are published in an article in the journal Chemosensors. “We get important information about a person’s health by measuring their exposure to heavy metals. High levels of cadmium can lead to fatal problems in the respiratory tract, liver and kidneys. Lead poisoning damages the central nervous system and causes irritability, cognitive impairment, fatigue, infertility, high blood pressure in adults and delayed growth and development in children,” said Paulo Augusto Raymundo Pereira, last author of the paper and researcher at IFSC-USP.

Humans eliminate heavy metals mainly in sweat and urine, and analysis of these biofluids is a central part of toxicological testing as well as treatment. “The world needs flexible sensors that can be easily, cheaply and quickly mass-produced, as our device is, for on-site detection, continuous monitoring and decentralized analysis of hazardous compounds,” he said.

Unlike other gold standard tests for detecting heavy metals in biofluids, the sensor is simple in terms of the materials used to make it and the stages in its production. “The basis of the device is polyethylene terephthalate [PET], on which there is a conductive flexible copper adhesive tape, a label of the kind you can buy from a stationary, with the sensor printed on it, and a protective layer of nail polish or spray. The exposed copper is removed by immersion in ferric chloride solution for 20 minutes, followed by washing in distilled water to promote the necessary corrosion. All this ensures speed, scalability, low power and low cost,” says Robson R. da Silva, a researcher at Chalmers University of Technology in Sweden and co-author of the paper.

The device is connected to a potentiostat, a portable instrument that determines the concentration of each metal by measuring differences in potential and current between electrodes. The result is displayed on a computer or smartphone using appropriate application software.

The system is simple enough to be used by non-specialists without training, as well as technicians in places like hospitals, clinics and doctors’ offices. The device can also be used in several types of environmental management situations. “Artesian wells, for example, are regulated and require constant monitoring to analyze water quality. Our sensor can be extremely useful in such cases,” said Anderson M. de Campos, first author of the paper and researcher at the University of Munich in Germany.

Refinements and possible patent

The performance of the sensor to detect lead and cadmium was evaluated in experiments with artificial sweat enriched under ideal experimental conditions. Adaptations are necessary before the device can be patented.

Until the invention was finalized, we found no reports of flexible copper sensors being used to detect toxic metals in sweat, but an anteriority search would likely turn up something similar, potentially blocking a patent application.”

Marcelo L. Calegaro, co-author of the article and researcher at IQSC-USP

To avoid this problem, he is working on improvements and additional applications. One idea would involve replacing the waste-producing corrosion stage of cutting in a paper machine. Another would be to use the same type of device to detect pesticides in water and food.


São Paulo Research Foundation (FAPESP)

Journal reference:

de Campos, AM et al. (2022) Design and fabrication of flexible copper sensor decorated with bismuth micro/nanodentrites to detect lead and cadmium in non-invasive samples of sweat. Chemosensors.

Researchers develop wearable sensor to detect heavy metals in sweat

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