Harvesting Human Generated Energy to Power Medical Sensors and Wireless Networks
The objective of this project is to develop an energy harvester that will harvest 250-500 mW power from human chest motion to power up medical sensors and wireless networks for military and civilian applications.
The vast majority of military trauma deaths occur prehospital and a significant portion of in-hospital mortality occurs in patients with no vital signs in the field. Thus, large opportunities exist for reducing trauma mortality through innovation in the prehospital setting. Miniaturized medical sensors and the recent revolution of ‘internet of things’ make the soldiers (or civilians) a part of wireless networks, where it is possible to monitor them in health or in trauma. Rapid developments in the fusion of wearable biomedical sensors, wireless and cloud based data transmission and portable diagnostic/decision systems have led to numerous hardware and software systems, defining a new philosophy of Mobile Health (mHealth). The applications go beyond battlefields and include assisted living, fitness and sports, telemedicine and rehabilitation, to name a few.
The critical need is to harvest enough human energy to power medical sensors and transmit the data through a network. For immobilized soldiers, this is challenging because most of the common harvesting methods cease to function. High frequency data transmission makes medical wireless networks energy intensive. WiFi is a popular choice for eHealth/mHealth patient monitoring. Unfortunately, WiFi consumes the most power, depleting 2000-2400 mAh Lithium batteries in 7-12 hours. This is unacceptable for large scale systems (hospital or military deployment) or remote area applications.
Our innovation is a device that takes breathing motion as an input in a minimally obtrusive manner, amplify the displacement and velocity by 25 to 100 times in a short time period. We use a miniature electromagnetic generator to produce enough power output that, when time-averaged, would produce 250-500 mW power after accounting for mechanical and electrical losses. A loosely wrapped elastic band with Velcro adhesive will be sufficient for the harvester that can be miniaturized and integrated with a soldier’s vest strap. In case the vest needs to be removed, the strap can be detached and mounted on un-injured part of the thoracic or abdomen region.
Our technology will allow medical monitoring without increasing the battery weight that soldiers already carry in their missions. Our product will also resolve the problem of low efficiency energy harvesting for human wearable (and not just patient monitoring) systems. Wearable wireless networks are considered the future of personal and social lifestyle as well as military communication systems. The current focus is on chest motion as an input. However, the design can be adapted to harvest energy from walking motion to extract 10 times more (5-7.5 W) power. This is because human weight is two orders of magnitude higher than chest force. This will be beneficial for the medical personnel with normal mobility.
The current technology readiness level (TRL) is 2.
Figure 1. Preliminary results: (a) 13 W LED bulbs, lighted with harvested power, (b) envisioned product.