Batteries are the lifeline of electronic items and gadgets. As technology advances, batteries tend to get smaller and capable of holding higher amounts of energy. The ubiquitous Lithium-ion batteries are used to power everyday gadgets – from laptops to portable speakers. Despite being lightweight and offering high energy density, they are often manufactured using non-biodegradable, toxic materials. Renewable energy harvesting equipment’s, such as solar cells and nanogenerators also contain nonrenewable and non-biodegradable heavy metals and polymers. Manufacturing and disposal of such batteries require high energy and could pose a potential threat to the environment.
The development of paper-based batteries could be encapsulated under the field of Papertronics, which offers cheap, sustainable, and eco-friendly batteries possessing fruitful mechanical and fluidic properties. The diameter of the paper’s cellulose fibers, its roughness, and transparency can be manipulated by cutting-edge engineering techniques – enabling it to be used for a number of applications. In the field of biosensors, paper has a unique advantage for being inexpensive, flexible, and disposable and also possessing high surface area. However, the power requirement of such sophisticated sensors was the driving force behind the development of bio-batteries.
Thus, researchers at the State University of New York at Binghampton, led by Seokheun Choi, developed a paper-based, single-use battery that uses bacteria to both generate electric current and consume the battery at the end of its lifespan. Exoelectrogens, a special type of bacteria that transfers electrons outside their cells, are freeze-dried on the surface of the paper-batteries. The battery uses respiration to convert the biochemical energy stored in organic matter into electrical energy, using a series of reactions through a system of electron-carrier biomolecules. The bacteria is activated by adding water and saliva, following which the bacteria’s make energy for themselves. The energy could be harnessed to power the battery, which can eventually power a LED or an electronic calculator. By combining paper with organic and biological entities, the battery could set the platform for next-generation electronics.
However, in 2017, researchers from Spain, Canada, and the U.S. developed a metal-free, portable, and biodegradable redox flow battery. Designed for single-use purposes, the battery operated for 100 minutes before being decomposed by soil-inhabiting microorganisms. Choi has pointed out a potential drawback of disposing such batteries, as they require favorable landfill conditions. Instead, his paper batteries have a shelf life of 4 months and readily decomposes in water.
The short-lived batteries could be used for a number of applications – from ingestible healthcare devices to sensors for intelligent transportation. By ensuring the devices are biodegradable, the environmental footprint of the batteries will be minimized. Although the current capacity of Choi’s batteries are minimal, it could be further developed to store more power and last longer.
It’s estimated that more than 50 billion electronic devices are set to be deployed in the next five years. A large portion of such devices will have a short working life and will require batteries that are produced from non-toxic, biodegradable materials to be easily disposed of. The field of Papertronics, advanced by the world of Choi and his colleagues, might hold the answer for the next generation of cheap, portable and disposable batteries.