It seems like every few months there's a new phone, a new laptop, or a new tablet that's so exciting people are lining up to get hold of it. While the constant adoption of newer, more advanced electronics products has made companies such as Apple hugely successful, the short shelf life of these electronics products is bad for the environment.
Modern electronics
are filled with circuit boards on which different metals and plastics are soldered together. Some of these materials are toxic - or decompose into toxic substances. Efforts are being made to promote the recycling of electronic waste, to recover reusable material and to dispose of the remainder properly. However, most appliances are added to the growing pile of electronic waste in landfills.
Printed circuit boards and other electronics can be very stacked. AP Photo / Michael Conroy
Instead of adding more waste to this ever-growing pile, it is possible to develop biodegradable electronics. That's why other researchers and I are focusing on the emerging field of paper-based electronics called "papertronics." They are flexible, even foldable, sustainable, environmentally friendly and cost-effective.
To be truly environmentally friendly, Papertronik can not use conventional batteries made of metals and corrosive acids to store and discharge electricity. Recently my chemistry colleague Omowunmi Sadik and I developed a paper battery that is recyclable, biodegradable, and reliable enough to actually be used. The key is bacteria.
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Flexible bio-batteries
I have developed flexible batteries, salivary batteries, and much more. I figured it makes sense to make a battery of paper if you want paper-based electronics. Fortunately, paper is a good potential battery material: it is flexible, a good insulator - which makes it a good platform for assembling electronic components - and absorbs and releases fluids easily. We added polymers - poly (amic) acid and poly (pyromellitic dianhydride-p-phenylenediamine) - to improve these electrical properties.
To store energy in the battery, we added bacteria instead of the metals and acids that chemically react to produce electrons. When these batteries are eventually commercialized, they use bacteria that are harmless to humans and the environment and are well entrapped to reduce any other contamination.
Because the paper is rough and porous, the bacteria adhere to it and generate their own energy by decomposing almost any available organic material, including plant material or wastewater. At the moment we pack the raw material, but it could also be from the environment. This chemical reaction generates electrons. Normally, these electrons bind to oxygen in a bacterial reaction, but we've built our battery to limit oxygen and replace an electrode. This means that we can capture the electron flow and use it to power devices.
We feared that oxygen could get into the paper and disrupt the flow of electrons between the bacteria and reduce the efficiency of the battery. We have found that while this happens, it has minimal impact. This is because so many bacterial cells adhere to the paper fibers. They form a multi-layered biofilm that protects the chemical reaction from most of the oxygen.
We also wanted a battery that is biodegradable. The bacteria in the battery itself, once released, can break down the paper and polymers into harmless components. In water, our battery is easily biodegradable, with no special equipment or other microorganisms that aid in its degradation.
The polymer paper structures are lightweight, inexpensive and flexible. Thanks to this flexibility, the batteries can also be folded like a normal piece of paper or stacked on top of each other. So more battery power fits into smaller rooms.
Promises and opportunities
Papertronik can be particularly useful in remote areas with limited resources as it is powered by bacteria that live in the most extreme conditions and decompose almost any material to produce electrons. You also do not need a well-established power grid. Although paper batteries are designed to be disposed of after use, their materials are recyclable - and new batteries can be made from recycled paper.
As revolutionary as paper-based bio-batteries are for future electronic devices, they are so easy to make. The polymers and bacteria may be blended with paper or even coated or cast directly onto paper in conventional manufacturing processes, including web printing and screen printing.
The paper batteries can also be added to other materials - such as metals, semiconductors, insulators and nanoparticles. These and other substances can give paper-based devices more features and capabilities, opening new doors for the next generation of electronics.
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