A Band-Aid That Monitors Your Activity

Being deeply immersed in the world of tech is enough to make a person feel like they have whiplash at times. The pendulum of progress seems to continually swing back and forth. At one moment, microservices may be all the rage. Then, when the complexity gets out of hand, monolithic applications become favored again — until the old problems that drove engineers to microservices in the first place reemerge and change the vibe once more.

On the hardware front, we are presently in an era of consolidation. You want a phone? OK, let’s just put a laptop-grade processor, ultra-high-resolution camera, loads of sensors, and the kitchen sink in there for you while we’re at it. The story is much the same for everything from smart watches to refrigerators these days. But there are some advantages to purpose-built devices that we lose out on with these all-in-one gadgets.

Maybe it’s time for the pendulum to swing back in the other direction? A group of researchers at Carnegie Mellon University and the University of California, Los Angeles believes that wearable devices, in particular, could benefit from being slimmed down. To demonstrate the potential of minimalistic wearables, they created a system that they call Hapt-Aids. These bandage-like devices are self-powered and custom-built for human activity monitoring — and nothing else.

Unlike smartwatches that need regular charging and have complex interfaces, Hapt-Aids aim for complete simplicity. They don’t need batteries, Bluetooth, or screens. In fact, they don’t even have microcontrollers or digital components. Instead, the system relies entirely on analog circuitry to harvest, interpret, and use energy from the user’s own movements or surroundings. Each device passively gathers energy from an activity, like walking, exercising, or even just laying in the sun, and uses that same energy both as a measurement of the activity and as power to notify the wearer when a certain threshold has been reached.

This is made possible by a small energy harvester, such as a piezoelectric element or solar cell, that captures energy from motion or light. That harvested energy is stored in a tiny supercapacitor. As the capacitor fills, its stored energy represents how much activity the user has done — for instance, how much they’ve walked or how long they’ve been in the sun. When the stored energy hits a preset level, an analog circuit releases it all at once into a vibration motor, producing a short haptic buzz. This tactile feedback lets the user know that their goal has been reached.

Through both laboratory and user studies, the researchers tested several Hapt-Aid prototypes powered by different energy sources — including motion, heat, and light. Each was able to generate enough power to produce a noticeable vibration, confirming that the concept works in real-world scenarios.

Hapt-Aids demonstrate that sometimes less really is more. By reducing cost, size, and maintenance requirements, they could make health and activity monitoring as simple as putting on a Band-Aid.