Electronics Sustainability: Building Circuits In Cellulose Paper With 10x Better Performance

Flexible and Sustainably Battery-Free Device with High Efficiency Radio-Frequency Energy Harvesting Function Fabricated on Paper by Researchers from Micro-Nano-Bio Systems Lab, Western University

A printer can print text and images, but also electronics. This new emerging printed electronics technology, which takes advantage of the existing graphics printing industry to produce flexible, stretchable, lightweight and wearable devices, constitutes a rapidly growing area of research, with the potential of reforming the electronics industry and changing our daily life.

Paper is ubiquitous in modern society and is compatible perfectly with all types and ages of printing technology. This positioning enables paper-based electronics to be seamlessly integrated into any paper-containing product with little-to-no change in infrastructure. More importantly, as a sustainable, low-cost and flexible substrate, paper-based printed circuit board (P-PCB) is considered to have about a two magnitude (~100x) lower impact on the environment than regular PCB, according to a recent study.

However, fabricating high-performance circuit on paper is challenging. Though it looks nice and smooth under human eyes, the paper is actually made of numerous cellulose fibers. These fibers can be clearly seen under a microscope, forming a surface with high roughness and high porosity. These micro-structures tend to absorb functional materials (e.g. nanoparticles in conductive inks) instead of leaving them on the surface. This prevents conductive materials inside the ink from contacting each other, making it impossible to form a highly conductive layer. Meanwhile, the excessive nanomaterial used to compensate the loss of conductivity also makes traditionally printed paper electronics not cost effective.

Prof. Jun Yang (Right), founder of the Micro-Nano-Bio Systems Lab, Western University and his Ph.D. student Tengyuan Zhang (Left), leader of the printed electronics project

To address these challenges, Prof. Jun Yang and his team from Western University, Canada, invented a scalable, cost-effective method to fabricate high-performance electronics on regular cellulose paper. Unlike the regular method, where conductive materials are printed onto the substrate directly, the newly invented method functionalizes the paper selectively with “seed”, a type of catalyst, to activate the growth of copper along each cellulose fiber.

The porous structure of the cellulose paper, which used to be drawbacks, are turned into advantages for three-dimensional generation of a highly conductive copper-fiber reinforced structure. The paper-based circuits fabricated by the research group shows ultra-low sheet resistant of ~5 mΩ/sq, almost 10 times better than what is currently available on the market (50 mΩ/sq). It is also worth mentioning that, the whole fabrication process does not involve any nano-materials, cutting the cost several times. This work was published on Advanced Sustainable Systems and was featured as the front cover of the journal.

Paper-Based High-Performance Ultra-Narrow Band Radio-Frequency Identification (RFID) antenna (left) and Battery-Free Self-Powered LED Light Array (middle, right). Both are fabricated using the newly developed technology by Prof. Yang’s group.

“Printed electronics has been popular in research for more than 10 years, but we seldom see printed electronics products on the market. Why? Because it still costs many times higher than printing a bar code but shows much lower performance than regular electronics,” said Prof. Yang, “Current printed electronics industries rely heavily on nano-materials, and nano-materials are far more expensive than regular materials. We want to change that, we want to improve the performance and lower the cost, and that’s the purpose of this project.”

Based on their research, Micro-Nano-Bio Systems Lab, founded by Prof. Jun Yang, is now offering FREE rapid prototyping service of high performance flexible printed circuits on three types of substrates: paper, polyethylene terephthalate (PET) and polyimide (PI).

“I believe that the importance of this research lays not in its results, but in its implications for the future. Thus, we decided to provide the PE prototyping service for free, to benefit more people and inspire them to conduct more world-changing science.”

This study, Facile Fabrication of Hybrid Copper–Fiber Conductive Features with Enhanced Durability and Ultralow Sheet Resistance for Low-Cost High-Performance Paper-Based Electronics was recently published in the journal Advanced Sustainable Systems.

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