In its ongoing quest to measure every aspect of U.S. troops’ physiology, the Pentagon’s esoteric research enclave wants to develop a durable, unobtrusive device that can track the body’s physical response to stress. Military scientists believe that using the device — preferably a tattoo — to track heart-rate, temperature or bio-electric response during various training situations will help them crack the code of combat fatigue.
Darpa, the same guys who are working on robot ostriches, battlefield illusions and a texting spy camera, recently requested research proposals to develop the next generation of bio-statistic devices. The solicitation, which opened last month, hopes new technologies can transcend the current paradigm of patient monitoring of needles, gels and electrodes. And advanced materials make it possible to integrate everything from the sensors to the transmitter into thumb-sized membranes that can stick to skin — like temporary tattoos.
Darpa is hoping that whichever company wins the research contract will be able to use a relatively new technology known as epidermal electronic systems (EES) to make sensors that are both unobtrusive and durable enough for modern combat training. Using state-of-the-art, highly flexible materials, researchers can coil sensors, electronics, and transmitters into serpentine shapes that form a stretchable net. “This innovative design contains all of the necessary components in an ultrathin layer about the thickness of a human hair,” writes Zhenqiang Ma, an electrical engineer at the University of Wisconsin, in a review of the technology.
They are nearly as flexible as hair, too, and adhere to the skin using strong molecular forces. According to research by EES’ inventors at University of Illinois at Urbana-Champaign, they can be pinched, poked, pulled, and stretched without damaging the device. In one experiment, researchers left a sensor tattoo attached to their subjects’ necks for over 24 hours before it wore off.
These tiny arrays combine the necessary sensor — be it EKG, heart rate, or temperature — with a short-wave antenna and transmitting capability. Using tiny power sources that collect solar energy or stray electromagnetic radiation, the data can be collected in real time and sent to handheld devices.
EES is a departure from traditional patient monitoring, but the technology is hardly perfect. Its transmission range is limited by its tiny power supplies, and sweat limits how long the tiny wafers can keep their grip.
This isn’t Darpa’s first foray into quantifying the combat experience. In the past it’s been interested inoverclocking cellular mitochondria; experimenting with sleep deprivation; and last year it even started tracking stress on a hormonal level. The body’s physiological responses can be used to measure many things, such as physical exertion, sexual excitement, or life-threatening danger.
Unsurprisingly, it’s the latter that Darpa is most interested in. While certain levels of stress are expected and even beneficial, excessive stress can be a serious drain on soldiers’ short-term readiness and long-term mental health. (Remember the last time you walked by the VA hospital?) Isolating the factors that make these stress levels spike is part of a larger initiative to understand and control the different triggers of the body’s physiological responses.
Another new technology also shows promise. Power Felt, the underwear that turns body heat into battery life, can harvest miles worth of transmission wattage. The fabric, invented in David Carroll’s materials lab at Wake Forest University, even passed an inadvertent swim test when Carroll’s wife accidentally put one of the shirts through the wash.
Carroll says it’s not a stretch to imagine his shirts being integrated with sensors, transmitters or a user interface. There’s even an existing model that can use its array of power modules to detect which areas of the body are producing the most heat. Considering blood is basically the body’s river of heat, this could have huge implications for remotely monitoring which soldiers are wounded and where. They’re durable, too: Carbon nanotubes woven into the fabric make rerouting around even large tears a snap.
Power Felt blankets the body, but Darpa favors a design that uses physiology to optimize sensor placement and signal processing. And the transmission range isn’t a huge factor — Darpa’s ambivalent as to whether the data is transmitted in real-time or downloaded post facto. This indicates that the eventual device will be some sort of tattoo. Let’s just hope they don’t call it a troop stamp.