Dr. Nguyen Ngoc Tan (University of British Columbia) and his team have successfully developed a type of battery that can stretch and is soft like fabric, designed for use in smart sensors.
Batteries for smart sensors are a popular technology trend today. For instance, in the biomedical field, there are applications that require patients to wear smart clothing for about 10 to 12 hours a day, even while sleeping.
Soft fabric-like battery developed for clothing.
Using a conventional battery would definitely cause discomfort and irritation for the wearer. “Without soft and safe batteries for body contact, it will be difficult to continue developing sensor-integrated clothing,” Dr. Tan stated.
Working at the Advanced Materials and Process Design Laboratory, Dr. Tan began exploring the field of flexible batteries in 2019 and noticed that while there had been much research, practical products were nearly non-existent. More importantly, “how to create batteries that last a long time (for example, several years) and are safe enough to wear, or even washable in a washing machine, has not been achieved by anyone yet,” Dr. Tan noted.
The key technology lies in the battery’s encapsulating material. This material must meet the requirements of preventing gas and liquid exchange to minimize the transport of molecules in and out of the battery; it should have a low modulus for compatibility with stretchable electronic devices;
It must be compatible with battery components and possess biocompatibility (non-harmful to the body), especially in applications that integrate seamlessly with the human body; it should be easy to manufacture, particularly by utilizing existing production processes; and it must exhibit mechanical and chemical durability throughout its usage, even when deformed during washing.
To address the issue of compatibility with the body, Dr. Tan’s research team chose zinc and manganese dioxide—safer materials compared to those in conventional lithium-ion batteries—to serve as the materials participating in the chemical reaction that generates electricity.
However, the key challenge and the most difficult aspect of this research was how to create a material that could prevent water from permeating the battery while also bonding the different layers of the battery together. If the battery layers are well bonded, they will move together when stretched or washed in hot and cold temperatures, thereby withstanding those impacts.
The team decided to use polymer—a readily available material that has been used in the medical field but never before in battery research. When experimenting with polymer, Dr. Tan’s research team discovered that this material not only has high chemical stability and biocompatibility but also exhibits the least water permeability compared to any other elastic materials.
After more than a year of experimenting and developing a new production process (as this type of battery is entirely different from conventional batteries), Dr. Tan’s team successfully developed a new battery comprising multiple ultra-thin layers containing a mixture of zinc and finely crushed manganese dioxide (to allow for stretching), bonded together by the same type of polymer.
When tested in a washing machine, the results showed that the battery developed by Dr. Tan’s team could “survive” 39 wash cycles while still functioning optimally. “It is evident that with this structure, the battery is waterproof and maintains its integrity through multiple uses,” the research team shared.
To further test the battery’s endurance, Dr. Tan’s research team conducted experiments with both cold and hot wash cycles (up to 80°C), each lasting about 1.5 hours. The test results indicated that the battery remained intact and functional after washing.
Following the success of this research, Dr. Tan stated that his team has closely collaborated with several companies pursuing smart clothing products to test the battery’s ability to meet real-world demands. Currently, the battery developed by Dr. Tan’s team operates at approximately 1.5V—lower than the 3V of lithium-ion batteries due to the need to balance capacity and safety.
