Sweat Stress
New Sweat Sensor Detects Stress Levels
Medical engineers from the California Institute of Technology (Caltech, USA) have developed a wireless sweat sensor that can accurately determine the level of cortisol – the stress hormone – in the body. In the future, it can be used in human health research on Earth and in space, according to the Caltech website.
A description of the new device appeared in the journal Matter (Torrente-Rodríguez et al., (Investigation of Cortisol Dynamics in Human Sweat Using a Graphene-Based Wireless mHealth System).
The sensor works much more accurately than other ways of measuring stress: surveys or blood tests. The first one does not give exact answers, since we cannot determine how strong or weak stress we are experiencing right now and whether we are experiencing it at all. The second one can greatly distort the results: the procedure itself, in which a needle is inserted into the skin to draw blood, can increase cortisol levels and distort the results.
The new device is made of graphene, a sheet form of carbon. With the help of a laser, a graphene "sheet" acquires a three-dimensional structure with tiny pores that help control sweating. These pores create a large surface area in the sensor, which makes it sensitive enough to detect compounds that are present in very small amounts in sweat. In the new sensor, these tiny pores are linked to an antibody, a type of immune system molecule specifically sensitive to cortisol, which allows the device to detect the hormone.
The sensor has been tested in two different ways. In the first test, a sensor was used to monitor the daily fluctuations of cortisol in a healthy person. The data necessary for the analysis were collected in six days. The sensor showed how cortisol levels rose and fell during the day. Monitoring the daily cycle of the stress hormone in a patient can reveal mental illnesses and stressful conditions.
During the second test, the scientists conducted two experiments. In this case, the sensor registered changes in cortisol levels that occurred in response to an acute stressor. In the first experiment, the subjects were asked to perform aerobic exercises (in which oxygen acts as the main source of energy for muscle work), since intense exercise causes a strong increase in cortisol. In the second experiment, the subjects were asked to immerse their hands in icy water – a stressor sufficient to release cortisol. In both experiments, sensors immediately detected a jump in hormone levels.
The new sensor can find many applications in typical medical applications here on Earth – and not only. It can also be useful in space. In October, NASA announced that the creator of the sensor, Wei Gao, is one of six scientists selected to participate in human health research on long-range space flights.
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