The researcher Edberg has a background in material science and nanotechnology and is now a project leader at RISE in the Swedish city of Norrköping and the scientific leader for the competence centre Digital Cellulose Center. For the last ten years, he’s been working with ”paper electronics”, aiming to develop more sustainable electronics than what is currently available.
— When I was a PhD student at Linköping University at the Laboratory of Organic Electronics, he says, I got involved in a project called Power Paper. The idea was to explore how electroactive materials could be combined with cellulose from wood to make flexible and paper-based electronic devices. I and my coworkers became especially interested in combining conjugated polymers (plastics that can conduct electricity) with a special form of cellulose called nano-fibrillated cellulose. The new paper-like material could not only be used to conduct electricity but also store electricity when put in a device called a supercapacitor, similar to a battery.
The team, Edberg continues, continued to develop the paper in several projects that followed, both to improve its performance, but also to be able to manufacture it in a similar way to how paper in made today.
— In the beginning, the papers were made in Petri dishes (used for the cultivation of bacteria, yeasts, plant, and animal cells on solid media, Ed’s note) in a cleanroom — not exactly a scalable manufacturing method compared to a real paper machine. However, when we tried to use manufacturing methods similar to paper making, we had problems making the conductive particles stick to the cellulose fibres. We believed that if it could truly be produced in a paper machine, then that would open up new possibilities for producing energy storage devices at a high rate, low cost, and with a smaller environmental impact compared to today’s technologies. This will be important in the future since the shift to renewable energy sources will require more and more energy storage devices since current battery technologies are not very environmentally friendly or safe.
The research continued within the Digital Cellulose Center. As mentioned, it’s a competence centre with the goal of making cellulose-based products an integral part of the digital society. Within the Center, developing sustainable electronics is one of the core goals. In 2021, the Center’s partners teamed up with two industrial partners to attempt to produce the Power Paper in a pilot-scale paper machine.
— At this point, we had learned more about how the electronic particles interact with cellulose, and we now believed that we could take the step from the gram scale to kilogram scale manufacturing. We planned to produce around 15 different paper rolls — each of them 10 meters long and each with a unique material composition and processing parameters. In doing so we hoped to learn more about the formation process of the electronic paper. We were hoping that we would be able to successfully produce at least one roll, but to our great surprise, most of the trials were successful. After testing the paper’s electrical performance, we could see that it had good properties for storing electrical energy when used as the electrodes in supercapacitors. The initial results have already been published as a pre-print in the repository ChemRxiv (Production of an energy-storage electrode paper using a pilot-scale paper machine), and the final version of the manuscript is currently under peer review. This year we have continued with more trials while we are still analyzing the large amount of data collected during the first production.
What have been the main obstacles and challenges throughout the process?
— In the early stages, the main obstacle was to make the conductive particles attach to the cellulose fibres. Papermaking is a kind of filtration method where water is removed from a mixture containing the fibres. What we saw was that the fibres would stick to the filter, but the smaller electroactive particles would pass through with the water. But through research, we learned how to chemically modify the fibres to make the particles stick. Right now, the main challenge is to make the paper strong enough to make it hold together when still in wet form. For this, we need to add additional components.
You mentioned it before, but how far have you come in the process and what are the next steps?
— Two trials were completed in 2021, one more this year, and another one will take place after summer. In each trial, we have learned something new about this quite complex material system, and the performance is getting better and better. We are also continuing the process of using the paper to assemble energy storage devices, and besides supercapacitors, we are exploring battery technologies where we think that the paper might have its greatest potential.
When do you think it can reach the market? And who will be the customer?
— In the coming years, we hope to take the production from a pilot scale to a full-scale paper machine. At this stage, the technology could be interesting for battery and supercapacitor manufacturers. But we are also exploring the paper for many other applications — with the knowledge gained from this project, we now have the tools to produce other types of electroactive paper technologies, says Edberg.
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