Flexible skin patches with biometric sensors have several advantages over devices that you strap on, clip to clothing, or carry. Skin patch sensors conform to the skin surface, are light in weight, comfortable, and easy to remember to wear if you never have to take them off. Skin patches also present opportunities for sensors to be powered by energy-harvesting or other non-traditional energy sources. Researchers from the University of Illinois at Urbana-Champaign and Hanyang University in Seoul developed a stretchable, battery-free skin patch that gets power via near field communication (NFC). Caltech scientists developed an electronic skin patch powered by sweat.

According to researchers at the University of Houston, neither traditional wearable devices nor skin patch sensors can collect biological data with sufficient accuracy for medical diagnosis and treatment. The UH engineers developed a new form of sensor electronics called “drawn-on-skin electronics” that are not affected by wearer motion. The team reported their development in Nature Communications.

The Houston electronic ink consists of three different inks that function as conductor, semiconductor, and dielectric materials. Freehand drawings on the skin with combinations of these inks can create transistors, strain sensors, temperature sensors, heaters, skin hydration sensors, and electrophysiological sensors, according to the researchers. The team also report success using the ink to track muscle signals, heart rate, temperature, and even “the ability to accelerate healing of wounds.”

In practical terms, most situations don’t have an engineer with drawing skills on hand to create sensors on your skin. Team leader Cunjiang Yu, an Associate Professor of Mechanical Engineering at UH, said the electronic ink capabilities would be particularly valuable in the field, away from other resources. The ability to create vital sign sensors quickly would be most helpful on a battlefield, Yu suggested as an example.

It occurs to me that possibly the UH electronic ink could be used with stencils or similar to temporary rub-on tattoos for emergency applications by non-technical personnel.