Two months ago, researchers from the State University of New York showed off their work on a bacteria-driven breakthrough paper cell.
“Paper as a biosensor material has unique advantages,” researcher Seokheun Choi explains. “It's cheap, disposable, flexible, and has a very high surface area. However, complex sensors require power. Commercial batteries are too wasteful and expensive. And they cannot be integrated into paper substrates. The best solution is paper bio-batteries."
Suddenly, office paper began to return. Well, at least in the electronics and battery fields.
The explosive growth of small electronic devices and batteries that support almost everything, from ingestible medical devices to smart transport sensors, has driven design innovations in these devices, and its environmental impact has also raised concerns.
It is estimated that more than 50 billion electronic devices will be put into use in the next five years. Many of these devices have a short life span and their rapid disposal will cause waste disposal problems.
The debut of "Electronic Paper" equipment provides electronics engineers with flexible, sustainable and eco-friendly materials at low cost and good mechanical, dielectric and fluid properties.
Seokheun Choi, an associate professor of electrical and computer engineering at the State University of New York, Binghampton, and colleagues have created a paper-based disposable battery that uses bacteria to generate electricity and breaks down the battery with bacteria after the battery has reached life.
In a paper published in the magazine AdvancedSustainableSystems, the authors write that lithium-ion batteries and supercapacitors can achieve high energy density, and they are lightweight and can be integrated into flexible substrates. But they also pointed out that lithium batteries are usually made of non-biodegradable materials and toxic materials, and the production process often consumes a lot of energy and is potentially harmful to the environment.
Other energy harvesting devices such as solar cells, nanogenerators, and thermoelectric generators contain large amounts of non-renewable and non-biodegradable heavy metals and high molecular polymers.
Choi said that once advanced engineering technology is applied, traditional office paper can provide a sustainable option.
Innovative engineering techniques can be used to manipulate the diameter of paper fibers, smooth out rough parts, and control transparency, making a range of applications possible. The combination of paper and organic, inorganic and biomaterials expands the possibilities of engineering design and makes paper a viable platform for next-generation electronics.
Part of the funding for Choi's research comes from a $300,000 grant from the National Science Foundation, which focuses on the integration of bacteria that produce electricity and handle batteries into paper. He created a paper-based battery in his initial work and was first reported in 2015. In his latest report released on August 19th at the 256th National Meeting & Exposition of the American Chemical Society, he described how to activate bio-batteries and how to extend their shelf life. His report also explains how the required energy is transferred to places where there is no electricity and powers a light-emitting diode and calculator.
Currently bacteria can survive for about 4 months in freeze-dried state, and researchers continue to look for ways to extend the shelf life of new paper batteries. Choi has applied for a battery patent and is seeking commercialization of industry partners. The research to date is funded by the National Science Foundation, the Naval Research Office, and the New York State University Research Foundation.
In the laboratory, bacteria-based batteries use the respiration to convert biochemical energy stored in organic matter into biomass. The process is carried out in a system that uses biomolecules as an electron carrier and contains a series of reactions that transfer electrons to the terminal electron acceptor, the positive electrode.
To make the battery, the research team arranged the dried "exoelectrogens" on paper. They explained that "electrically produced bacteria" is a kind of bacteria that can transfer electrons outside the cell. The electrons are supplied from the cell membrane and contacted with the external electrode to supply power to the battery.
To activate the battery, the researchers added water or saliva, both of which allowed the bacteria to reactivate. In the laboratory, the microbial battery produces a maximum power of 4 μW/cm 2 and a current density of 26 μA/cm 2 . Choi said these two parameters have been “significantly improved” compared to previous microbial cells. Even so, the power performance is "very low", limiting the application of the battery, at least for now. For commercial use, the power/current density must be increased by a factor of about 1,000, Choi said.
"The advantage of using paper as a device substrate is that you can easily stack or fold them to achieve series or parallel," Choi said. The origami process will become very useful.
As he did in early 2015, Choi created a battery inspired by origami that can be folded into a matchbox-sized square. It uses a cathode that is in contact with air and is sprayed with nickel at one end of the paper. The total cost of this device is five cents.
The current shelf life of this paper battery is about 4 months. Choi said his latest hybrid paper-polymer biobattery is very susceptible to degradation in water.
Choi and colleagues are not the only team to research paper-based batteries. In 2017, researchers from Spain, Canada, and the United States described a portable, disposable, metal-free, biodegradable redox flow battery. After working on a cellulose-based battery for 100 minutes, they were broken down by microorganisms in the soil, similar to the working process of backyard compost piles. Choi says one potential disadvantage of this approach is that the biodegradability of the battery depends on good landfill conditions.
Choi is currently studying how to optimize the survival rate and performance of freeze-dried bacteria, so that the shelf life of the battery is longer. He also patented the battery and is now looking for a commercial partner.