Digital wearable Health Tech devices require power, and this usually takes the form of electricity. Some devices can harvest the energy that they need from their surroundings, using heat, motion, light, or even radio frequency (RF) waves, but most devices use some sort of battery storage. One key design goal is to make the device run as long as possible on the energy stored in the battery. Other goals such as making the device small or lightweight run counter to the desire for long run times, as they require a smaller battery that can hold less energy.
One way out of this problem is to create a design that draws less energy from the onboard storage. Some devices spend most of their time listening for a trigger that will cause them to perform some action. This trigger might occur when the user presses a button, or sends a signal from a smartphone, or some sort of motion is detected. This idle time spent listening for the trigger can represent a major portion of the energy budget for the device. Researchers at the University of Bristol have come up with a listening chip that consumes no power while waiting for the trigger signal. This means that the rest of the device can be shut down, with no drain on the battery.
The magic comes from the fact that the switch can be powered by the tiny voltage created by a sensor, such as a photodiode that detects light. 650 mV is all that’s needed, which in turn can turn on a switch that powers up the rest of the device so that it can perform its operations. This chip can also detect the output from other sensors, such as accelerometers (motion detection) or RF signals. The end result will be devices that require smaller batteries yet still have long operational lifetimes. Wearables will be smaller, lighter, and more useful as a result.