Scientists are developing biofuel cells that power wearable electronics solely from human sweat. The study is published by the Journal of Power Sources.
The miniaturization of electronic devices has made huge strides over the past few decades. Today, after smartphones and the multitude of wireless options, there is a special type of device whose development is steadily moving forward. We are talking about wearable biosensors. These tiny devices are usually designed to be worn directly on the skin to measure specific biosignals. Data from them are sent wirelessly to smartphones or computers to track the user’s health.
The problem is that such devices need to be constantly charged and finding a suitable power source for wearable biosensors is difficult. Traditional batteries used in wristwatches and pocket calculators are too thick and bulky. Thinner batteries pose problems with capacity and even safety. But what if humans themselves were the power supplies of wearable devices?
A team of scientists led by Assistant Professor Isao Shitanda of the Tokyo University of Science, Japan, is studying effective ways to use sweat as the sole source of energy for wearable electronics. In their latest study, published in the Journal of Power Sources, they presented a new biofuel cell array design. It uses a chemical constituent of sweat – lactate – to generate enough energy to operate the biosensor and wireless devices for a short time.
The new array of biofuel cells looks like a paper bandage that can be worn, for example, on an arm or forearm. Basically, it consists of a water-repellent paper base on which several biofuel cells are laid out in series and in parallel. The number of cells depends on the output voltage and the required power. In each of these, an electrochemical reaction between lactate and an enzyme present in the electrodes produces an electrical current. It, in turn, moves towards a common pantograph made of conductive carbon paste.
This is not the first lactate-based biofuel cell, but several key differences set the new design apart from existing biofuel cells. In particular, the device is manufactured using screen printing. This method is suitable for cost-effective mass production.
The study was conducted in collaboration with Dr. Seiya Tsujimura of the University of Tsukuba, Dr. Tsutomu Mikawa of RIKEN, and Dr. Hiroyuki Matsui of Yamagata University, all in Japan.