New health monitoring patch uses harvested energy

The team, from Japan’s Osaka University in partnership with Joanneum Research in Weiz, Austria, hopes that the work could lead to advances in autonomous health sensors and battery-free wearable electronic devices.

Published in Nature Communications, the team’s paper details how the ultraflexible patches with a ferroelectric polymer can sense a patient’s pulse and blood pressure, powering themselves through normal movement. 

The need for wires or batteries can be inconvenient in providing power to wearable devices, something researchers aim to overcome with this method. The ability for integrated health monitors to use ambient motion to power and activate sensors could also accelerate adoption in doctor’s offices, the team said.

According to researchers, the key was starting with a substrate just one micron thick. Using a strong electric field, ferroelectric crystalline domains in a copolymer were aligned so that the sample had a large electric dipole moment. 

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Based on the piezoelectric effect, the device responds rapidly to strain or pressure changes. These voltages can either be transduced into signals for the medical sensors or to directly harvest that energy.

“Our e-health patches may be employed as part of screening for lifestyle-related diseases such as heart disorders, signs of stress and sleep apnea,” said first author Andreas Petritz.

The authors estimate that multilayer patches can harvest up to 200 millijoules per day from biomechanical motions if placed on joints like knees or elbows — enough to monitor cardiovascular parameters several times a day. The thin patches are ‘barely perceptible’, the team said, which could make daily health monitoring less unpleasant for patients.

“We expect that our findings will assist in the development of other sheet-type sensor systems that can perform precise biomonitoring when affixed to the skin surface,” said senior author Tsuyoshi Sekitani.