BY Fast Company 3 MINUTE READ

Sensors placed on your skin are powerful tools for doctors. They can measure your temperature, hydration, heartbeat, and muscle strain. The problem is that their hardware can be bulky, invasive, and expensive. Wearing an EKG tracker can feel like mummifying your body in wires.

But a new technology out of the University of Houston, led by Associate Professor Cunjiang Yu, solves all of these problems. His team has developed “drawn-on-skin” electronics. Quite literally, they have demonstrated that you can take a ballpoint pen, fill it with a special semiconductor ink containing elements like silver, and draw specific diagnostic sensors right on your body. These sensors get their energy from a nearby wireless battery pack, and send/receive data via Bluetooth.

You may think you’ve seen this idea before. Similar-looking, gold-based circuit tattoos have been demonstrated for years, which stick on your skin to serve as a form of electronic identification, a touch-skin controller for another device, or a means to monitor various aspects of your health. But as Yu—who hails from the University of Illinois where that first tattoo technology was developed—explains, the very act of drawing sensors, as opposed to preprinting them, comes with all sorts of benefits.

First and foremost, applying this advanced technology is decidedly low-tech. Heck, it’s easier than using a Spirograph. To apply, the stencil is taped onto the skin. The doctor (or even a patient) traces its line with a ballpoint pen filled with special ink. And after five minutes of drying time, the ink adheres to the skin and the stencil is removed.

Drawn directly onto the skin (without forcing you to shave first), that ink fills the unique crevasses of your body, tracking data with a level of fidelity that preprinted circuits can’t. “Every person is different,” says Yu. And accommodating these differences means that the drawn electronics fit perfectly, stretching with your skin, and they can easily last a week at a time while resisting sweat. Then if part flakes off, you can draw over it again, like you’d fix a sketch on paper. There’s no need to acquire a whole replacement tattoo.

As Yu explains, the breakthrough here is not just the ink (which could be formulated in all sorts of ways, he argues), but the entire interface of application, which needs neither expertise, nor a clean room to apply. So Yu imagines that you could get a special pen and stencil shipped to your home to draw on yourself, or you could get a quick sketch placed on your arm at the gym to measure vitals while exercising. Obviously, it’s a technology that would be comfortable in the developing world, too, where doctors and specialised equipment can be scarce. The cost? “Let’s say a dollar,” Yu laughs, before clarifying—maybe it would cost a few dollars for advanced circuits. In any case, the product is extremely cheap to manufacture.

But can these sensors do anything all that useful? Indeed, they can. We’ve seen that constantly monitoring someone’s temperature can spot COVID-19 outbreaks early, and Yu has proven that, when applied to wounds, his system can send out electrical impulses that speed up the healing process. Muscle strain monitors can be used to track someone’s gait and analyze their physiology for training or rehabilitation. And the medical industry is increasingly recognizing hydration monitoring as an important tool, especially for the elderly in hospitals, as up to 17% of elderly people admitted for dehydration will die in care. In any case, draw-on electronics offer the capability of advanced wearable electronics with the promise of lower costs and greater customisation. Ink-based electronics, drawn by your own hand on your own body, are the definition of democratised technology.

Since publishing the research last week, Yu has already received calls from several parties interested in licensing the technology and co-developing it further. Hopefully, it can come to market soon, and stays affordable in the process.

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