Scientists at Osaka University, in cooperation with JOANNEUM RESEARCH (Weiz, Austria), introduced wireless health monitoring patches that use integrated piezoelectric nanogenerators to fuel themselves with the harvested biomechanical energy. This work may lead to new self-contained health sensors as well as portable, battery-less electronic devices.
As wearable technology and smart sensors become more and more popular, the problem of powering all these devices becomes more relevant. While the power requirements of each component may be modest, the need for wires or even batteries becomes cumbersome and inconvenient. This is why new methods of energy recovery are needed. Additionally, the ability of built-in health monitors to use ambient motion to both power and activate sensors will help accelerate their adoption in doctor’s offices.
Now, an international team of Japanese and Austrian researchers have invented new ultra-flexible patches with a ferroelectric polymer that can not only sense a patient’s pulse and blood pressure, but also fuel normal movements. The key was to start with a substrate only one micron thick. Using a strong electric field, the ferroelectric crystal domains in a copolymer were aligned so that the sample had a large electric dipole moment. Based on the piezoelectric effect, which is very effective in converting natural movement into small electrical voltages, the device responds quickly to changes in stress or pressure. These voltages can be transduced either into signals for medical sensors or to directly harvest energy. “Our e-health patches can be used to screen for lifestyle-related illnesses such as heart problems, signs of stress and sleep apnea,” says lead author Andreas Petritz.
The authors estimate that the multi-layered patches can harvest up to 200 millijoules per day from biomechanical movements if placed on joints, such as the knees or elbows. This is enough to monitor cardiovascular parameters several times a day. And the patches are so thin that they are barely noticeable making a necessary ailment for many patients – daily health monitoring – less unpleasant.
“We hope our results will aid in the development of other sheet-like sensor systems that can perform accurate biomonitoring when attached to the skin surface,” says lead author Tsuyoshi Sekitani. Additional modules allow other functionalities, such as wireless communication with a smartphone or computer.
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