Batteries not required: self-powered wearable monitors health

A self-powered, wristwatch-style health monitor, developed by researchers at the University of California, Irvine, can keep track of a wearer’s pulse and wirelessly communicate with a nearby smartphone or tablet — without needing an external power source or battery. In a paper published in the journal Nano Energy, researchers from UNI’s Henry Samueli School of Engineering described their innovation, built via 3D printing of nanomaterials on flexible substrates for real-time and wireless monitoring of vital signs. The current prototype serves as a self-powered radial artery pulse monitor, but can also gauge other aspects of health, such as heart rate, body temperature or blood pressure, by changing the sensor circuitry.

Senior co-author Rahim Esfandyar-Pour, UCI assistant professor of electrical engineering and computer science and biomedical engineering, said the self-powered and wireless device allows users to monitor a person’s vital signs urgently and accurately, in situations where there is a need to keep track of health information on demand. “This device allows you to do that without relying on a battery that can lose its charge and has the thermal runaway issue [overheating of lithium-ion batteries that can lead to combustion],” Esfandyar-Pour said.

The device delivers health information in two ways. In one mode, the energy created by tapping the wristband’s nano energy generators powers up the sensor circuitry, and the wearer’s pulse rate soon appears as a flashing signal on an LED display. The second mode works when a smartphone or similar device is held near the wearable. Embedded near-field communication technology facilitates the wireless exchange of power and data between the wristband and the mobile device, and biophysical information is plotted and displayed on the smartphone’s screen.

The on-demand and self-powered characteristics of the invention are made possible by triboelectric nanogenerators (TENGs) that produce voltage through mechanical thumping or pressure. The TENGs are fabricated using titanium-based MXenes, a relatively new class of ultrathin 2D material with unique electrical and mechanical properties. A few atoms thick, MXene layers are bendable, stretchable and can be printed onto the surface of flexible, bandage-like material or a wearable arm- or wristband.

“This innovation achieves many significant outcomes in one package. It enables continuous, battery-free, wireless and on-demand health monitoring anytime and anywhere. It’s made with low-cost and flexible materials and can be tailored to meet a variety of wearable bioelectronic sensors’ requirements. It’s a flexible, completely configurated system,” Esfandyar-Pour said.

Image courtesy of the study authors, published in Nano Energy.