Is Sweat Up To Batt?: Sweat as a Power Source for Screening

In this technological era, wearable health monitoring devices have seen a significant uptick in recent years. The use of such devices is important in the detection of existing conditions, identifying markers that may indicate an increased risk for certain conditions, or performance monitoring in sports.

In many of these devices, a simple color change or read out can provide a real-time evaluation of the individual’s physical condition. Most of these devices are not meant for long-term use and are made to be disposable. One of the biggest issues faced in this industry is the difficulty of integration with the bulky electronics that can process the data received from the test to provide an accurate read out, especially in devices not meant for long-term use.

In this interesting study, Ortega and co-workers have developed a prototype screening device that screens for cystic fibrosis (CF). Cystic Fibrosis is a genetic disease that can cause lung infections and increased respiratory difficulty over time. For a long time, this was considered a terminal illness, but with medical advances, the life expectancy now exceeds 37.5 years, the previous life expectancy of a person with CF. This new method will provide a quick and easy test that will not require the presence of medical professionals.

As CF affects the viscosity of bodily fluids, which results in an increased salt concentration in the sweat of affected persons, making it possible to differentiate affected individuals by testing the sweat conductivity, which is directly affected by salt concentrations. A typical salt concentration reading of sweat from a person that does not suffer from CF is under 60µM, which roughly translates to a 1.2V conductance reading in the fabricated device. Since this is designed to be a screening test, the output is simply a positive or negative result, using 1.2V or 60µM as the threshold for a positive readout.

Figure 1. Illustration of screening device

In this device, the person’s sweat acts as the power source for the detector, using the salt concentration in the sweat as the conductor between the cathode and anode in the electronic portions of the device. The anode and cathode are connected only by a square of paper as shown in Figure 2b, assuring that a readout is not given without the paper fully soaking through, preventing any false negatives from occurring in the event of partial soaking, or an inadequate sample size. Using artificial sweat samples, this group has tested the device, resulting in 95% sensitivity and 100% specificity. The size and cost of the device will allow it to be used as a disposable, similarly to existing glucose sensors.

Figure 2a. Illustration of internal electronics b. Photograph of back side of device

This device is a significant development in sensing as the sweat generated doubles as both the sensor and the power source for the device, minimizing the number of components that need to be integrated into the electronics and making it energetically independent.

While this shows great promise for use in the medical field, there is much room for the development of similar devices that can be actively used in the monitoring of general health. In addition to being a promising prototype for screening CF, this device also sheds light on the potential for real-time monitoring of chemical levels in a quick and simple manner.  

Using Sweat as a Power Source for Detection of Cystic Fibrosis

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