Thanks to science and modern medicine, we know a lot more now about the early signs of certain diseases and which biomarkers to check. Most importantly, we have the necessary devices and techniques to conveniently sample and analyze these biomarkers in clinical settings so that doctors, patients, and caregivers can act accordingly. In the ever-evolving field of healthcare technology, wearable electronics and biosensors are seen as potential game changers, as they allow both medical staff and non-medical people to remotely monitor relevant bodily variables.
In the specific case of diabetes—a relatively common disease—monitoring blood sugar levels is crucial. Fortunately, urine sugar levels provide indirect information about blood sugar levels and can be used as an alternative biomarker to avoid drawing blood constantly. Moreover, to measure urine sugar levels in elderly or long-term care patients, sensors can be embedded directly into their diapers. By wirelessly transmitting the acquired data, diaper sensors can greatly simplify caretaking and health monitoring tasks. However, both sensors and wireless transmitters require an energy source to function and putting batteries in diapers may be a questionable solution from both environmental and practical standpoints.
Fortunately, scientists from Japan have worked out a solution to this problem. In a recent study published in ACS Sensors, Associate Professor Isao Shitanda, Professor Masayuku Itagaki, and Mr. Yuki Fujimura from Tokyo University of Science (TUS), Japan, present a promising approach to realizing self-powered diaper sensors that can generate energy directly from urine. This work was done in collaboration with Associate Professor Seiya Tsujimura from the University of Tsukuba, Japan. Worth noting, this work is in line with other research efforts of Dr. Shitanda and his colleagues to develop self-powered biosensors like a lactate sensor energized entirely by sweat.
But how does one generate enough electricity from urine to power a sensor? The answer lies in electrochemistry. The scientists developed a paper-based biofuel cell that, through a pair of reduction-oxidation reactions, outputs electrical power proportional to the amount of glucose in the urine. Important considerations in the design of such biofuel cells are the amount of urine needed to generate enough power and the overall stability and durability of the device. With this in mind, the scientists developed a special anode, the negative terminal of an electrochemical cell, using a process known as “graft polymerization” that allowed them to firmly anchor glucose-reactive enzymes and mediator molecules to a porous carbon layer, which served as the base conductive material.
The scientists tested their self-powered biosensor in diapers using artificial urine at various glucose concentrations. They used the generated energy to power up a Bluetooth Low Energy transmitter, and remotely monitored the measured concentration using a smartphone. They found that the biofuel cell could detect urine sugar in a very short time (within 1 second).
“Besides monitoring glucose in the context of diabetes, diaper sensors can be used to remotely check for the presence of urine if you stock up on sugar as fuel in advance. In hospitals or nursing care sites, where potentially hundreds of diapers have to be checked periodically, the proposed device could take a great weight off the shoulders of caregivers,” comments Dr. Shitanda.
In short, the sensor that Dr. Shitanda’s team has engineered can not only prevent diabetes, but also make diaper management more efficient and responsive without compromising the environment. “We believe the concept developed in this study could become a very promising tool towards the general development of self-powered wearable biosensors,” says Dr. Shitanda.
Let’s hope future studies will further improve upon wearable biosensors powered by our own body fluids.
Titles of original papers: Self-Powered Diaper Sensor with Wireless Transmitter Powered by Paper-Based Biofuel Cell with Urine Glucose as Fuel
Journal: ACS Sensors
About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.
With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society", TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.
About Associate Professor Isao Shitanda from Tokyo University of Science
Dr. Isao Shitanda graduated from Tokyo University of Science in 2001 and then got a PhD from The University of Tokyo, Japan, in 2006. Since 2012, he has been an Associate Professor at the Department of Pure and Applied Chemistry at Tokyo University of Science, where he leads the Itagaki/Shitanda lab. He specializes in electrochemical micro/nanosystems, physical and analytical chemistry, bio-related chemistry, and environmental chemistry, among other fields. He has published over 180 papers and holds seven patents.
This work was partially supported by JST-ASTEP Grant Number JPMJTS1513, JSPS Grant Number 17H02162, and the Private University Research Branding Project (2017−2019) from the Ministry of Education, Sports, Science and Technology.
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Self-Powered Diaper Sensor with Wireless Transmitter Powered by Paper-Based Biofuel Cell with Urine Glucose as Fuel
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The authors declare no competing financial interest.