Wearable sensor patch runs on energy harvested from user’s body heat


Scientists across the world are working to created a new class of electronics that are safely and efficiently powered by the human body. Last November, for instance, a team developed an innovative electronic watch that runs on the energy harvested from the movement of the wearer’s hands. As part of another project, researchers from Carnegie Mellon University devised digestible electronic “pills”, driven by the natural juices present in our stomach. At the recently-held Consumer Electronic Show (CES), we came across a smart wireless wearable sensor patch, programmed to monitor the user’s hydration levels, which derives all its power from the wearer’s own body heat.

The new technology is based on the fact that any sort of energy gradient can exploited be utilized as a power source. The human body, for example, creates its own energy gradient, by being relatively warmer than the surrounding environment. Thermoelectric materials are widely utilized to convert such temperature differences into usable electricity. Designed by scientists at North Carolina State University’s Center for Advanced Self-Powered Systems of Integrated Sensors (ASSIST), the wearable sensor is one of the many flexible thermoelectric generator (TEG)-based electronic devices currently being developed at the NSF-funded research center.

Measuring around 7 square centimeters, the contraption can generate roughly between 40 and 50 microwatts of power per square centimeter of its area, when applied to the user’s skin. Fitted by an array of powerful, flexible TEGs, the patch’s capacity to harvest energy from the wearer’s body depends chiefly on the temperature difference between the skin and the air. According to the researchers, on an average, 40-50 microwatts of electricity is produced as a result of a temperature difference of only 3 degrees Celsius, i.e. in the absence of any airflow or heatsink in the wearable sensor’s vicinity.

If airflow is present, like when you are walking or jogging, the device becomes significantly more efficient, with its electricity-generating capacity increasing by three folds. Although incapable of producing sufficient energy to drive a display or a GPS device, the new technology could be used to run low-power processors and sensors, such as hydration monitors, accelerometers, pressure sensors, EKG monitors, temperature sensors and so on. As part of the project, the team at ASSIST is also developing a low-energy Bluetooth system that could allow the wearable contraption to send data directly to the user’s phone.

As the scientists point out, the research is a step closer to self-powered wearable sensor electronics that don’t have to be taken off for charging. The team is currently trying to improve the sensor’s ability to harvest energy from the wearer’s body, without diminishing its flexibility and durability.

To learn more about ASSIST and its various research projects, head over to the organization’s official website.

Via: IEEE Spectrum

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