Roll-up computer screens and other flexible electronics are getting closer to reality as scientists improve upon a growing number of components that can bend and stretch. One team now reports in the journal ACS Applied Materials & Interfaces another development that can contribute to this evolution: a low-cost conductive paper that would be easy to manufacture on a large scale.
Current flexible electronic prototypes are commonly built using polymer thin films. But the cost of these films becomes a factor when they are scaled up. To address this issue, scientists have turned to paper, which is renewable, biodegradable and a fraction of the cost of polymer thin films. The downside of paper is that it's not conductive, and efforts so far to infuse it with this property have been hindered by scalability and expense. Bin Su, Junfei Tian and colleagues wanted to come up with a new approach.
Using a conventional roller process that's easy to scale up, the researchers coated paper with soft ionic gels to make it conductive. They sandwiched an emissive film between two layers of the ionic gel paper. When they applied a voltage, the device glowed blue, indicating that electricity was being conducted. It also showed electrical durability, withstanding more than 5,000 cycles of bending and unbending with negligible changes in performance and lasting for more than two months. The researchers say their conductive paper, which costs about $1.30 per square meter and could be fabricated at a rate of 30 meters per minute, could become an integral part of future flexible electronics.
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More information: Minghui He et al. Ionic Gel Paper with Long-Term Bendable Electrical Robustness for Use in Flexible Electroluminescent Devices, ACS Applied Materials & Interfaces (2017). DOI: 10.1021/acsami.7b02433
Conductive paper has low-cost, lightweight, sustainability, easy scale-up, and tailorable advantages, allowing for its promising potential in flexible electronics, such as bendable supercapacitors, solar cells, electromagnetic shields, and actuators. Ionic gels, exhibiting a lower Young's modulus together with facile manufacturing, can fully serve as the conductive component to prepare conductive paper. Herein we report a low-cost (∼1.3 dollars/m2), continuous, and high-throughput (up to ∼30 m/min) fabrication of reliable and long-term (stable for more than two months) conductive paper. As-prepared conductive paper shows a high electrical durability with negligible bending–recovering signal changes over 5000 cycles. Using this ionic gel paper (IGP) as a key component, we build a variety of proof-of-principle demonstrations to show the capacity of IGP in constructing flexible electroluminescent devices with diverse patterns, including a square, an alphabetic string, and a laughing face. Our methodology has the potential to open a new powerful route to fabricate bendable conductive paper for a myriad of applications in future flexible electronics.