Researchers Develop Sweat-Powered Biofuel Cells for Wearable Electronics
In a collaborative research effort, scientists from Japan developed a way of generating electricity from sweat using wearable biofuel cells.
Researchers from the Tokyo University of Science (TUS) along with research collaborators from the University of Tsukuba, the Riken Institute, and Yamaguchi University, Japan, have developed and tested a wearable biofuel cell array that can be used to generate electric power from a person’s sweat.
This could be the next step forward in generating a low-coHeading 5st, energy-efficient health monitoring tool that is less bulky and more comfortable to wear than devices that are currently available on the market.
Lactate reacts with an enzyme present in the electrode of the biofuel cell to generate electricity. Image used courtesy of TUS
Wearable Biosensors
Wearable biosensors and electronic devices are continually being developed and refined to meet medical and consumer market needs. Heart rate sensors, blood pressure sensors and smartwatches are just some of the kinds of devices that are being developed to be more compact, user-friendly, and durable by tweaking aspects such as battery structure and power, weight, connectivity, and interface design.
Wearable biosensors are devices that can be used to measure biological or chemical substances that are produced by the individuals that wear them. These substances or biomarkers can be identified in bodily fluids such as saliva or sweat. They could be used to analyze and assess human physiologic parameters in real-time, whether this be for monitoring disease, general state of health or athlete performance. Over the years, researchers have created flexible circuits and electrodes for wearable electronic devices, but have not yet come up with a suitable method of powering wearable biosensors.
From Sweat to Power
In research led by Associate Professor Isao Shitanda from TUS, the different ways in which sweat might be used to power wearable electronics was explored. Professor Shitanda along with research collaborators Dr. Seiya Tsujimura from University of Tsukuba, Dr. Tsutomu Mikawa from RIKEN, and Dr. Hiroyuki Matsui from Yamagata University, published their research in the Journal of Power Sources.Together, the team created a biofuel cell array that uses the chemical lactate to power a biosensor and wireless communication devices for a short period of time.
The Tokyo University of Science. Image used courtesy of TUS
The wearable biosensor is made by placing multiple biofuel cells in a series and in parallel onto a water-repellant paper substrate. The number of cells can be adjusted depending on what output voltage and power is required. The cells are powered through a reaction with a substance found in sweat, known as lactate. Lactate is an electronically charged form of lactic acid. It is produced by the brain, red blood cells, muscle cells, and other cells during oxygen deficient energy production. Within the biofuel cells, lactate reacts with an enzyme present in the electrodes to generate electricity. Electricity flows to a current collector and made from conductive carbon paste.
In comparison with other lactate-based biofuel cells, Professor Shitanda and colleagues’ cells differ in that they can be made using a technique known as screen printing. It involves the use of porous carbon ink as a conducting path and can be used for cost-effective mass production. Another key feature of the biofuel cells concerns how lactate is drawn into them. Lactate from sweat passes through paper layers via capillary action. This is similar to the process of soaking up spilled water with a cloth.
In a news release, Dr. Shitanda commented on the power of the biofuel cells: "In our experiments, our paper-based biofuel cells could generate a voltage of 3.66 V and an output power of 4.3 mW. To the best of our knowledge, this power is significantly higher than that of previously reported lactate biofuel cells."
Through further testing, Dr. Shitanda and colleagues were able to demonstrate that one their fabricated self-driven lactate biosensors could power itself using lactate and measure the lactate concentration in sweat, and also transmit measured values o a smartphone via a low-power Bluetooth device in real-time.
The biofuel cells may not only serve as lactate biosensors for monitoring athlete training or patient rehabilitation but could be used for other wearable electronics.
In the same news release, Dr. Shitanda said: "We managed to drive a commercially available activity meter for 1.5 hours using one drop of artificial sweat and our biofuel cells.” Dr. Shitanda went on to say: “We expect they should be capable of powering all sorts of devices, such as smartwatches and other commonplace portable gadgets."
