Researchers develop sensor to detect stress from perspiration

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A team of researchers at the USA's California Institute of Technology has developed a sensing system that can rapidly, reliably and non-invasively evaluate levels of cortisol, a hormone associated with stress and anxiety. In the future, the new device may be used in space to monitor astronauts' levels of stress.

Assessing the intensity of physiological stress is a scientific challenge. Traditionally, the sensation of stress is measured from questionnaires submitted to patients, a method that has the disadvantage of relying on subjective impressions. Another established technique is blood sampling, which is more objective, but for which the margin of error is still high, given the apprehension a person may feel at the sight of a syringe. 

In a bid to obtain more accurate data, a team of scientists at the California Institute of Technology) have developed a sensor to evaluate stress from levels of cortisol, a hormone traditionally associated with stress, in sweat samples. The team led by researcher Wei Gao have now published details of their work in the journal Matter. The new inexpensive device is made from graphene etched with a laser to create a 3D-structure of tiny pores, which is coupled with an antibody that is specifically sensitive to cortisol. 

Wei Gao and his team conducted several tests. The first involved a volunteer with no particular health issues who agreed to have samples of his sweat tested over a period of six days. The sensor detected significant changes in cortisol levels throughout the day, with peak levels in the morning followed by a gradual decline, which is a standard pattern in a healthy person.

In a second experiment involving several participants, volunteers were instructed to engage in aerobic exercise, which is known to increase cortisol levels. Thereafter, the same volunteers were told to plunge their hands in ice water, a stressor that is sufficient to trigger the release of the hormone. In both experiments, the sensor immediately detected increases in cortisol levels.

A tool that could be used to detect depression

For scientist Wei Gao, the new device not only has the potential to reduce the harmful impact of stress on health, but also to detect mental disorders such as anxiety, post-traumatic stress and depression, all of which are correlated with changes in cortisol levels. "Depression patients have a different circadian pattern of cortisol than healthy individuals do," explains the researcher.

The research team further draw attention to the fact that the new device is not only non-invasive but also very fast, capable of gauging cortisol levels in just a few minutes, when a blood sample takes one to two hours to collect and analyze. 

Last October, NASA announced that Wei Gao has been selected to be one of six researchers that will participate in studies of human health on deep-space missions. Wei Gao's team will receive funding to adapt his sensor into a system for monitoring astronaut stress and anxiety under the program administered by the Translational Research Institute for Space Health (TRISH).