The art of Kirigami and paper electronics

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Researchers are using the ancient art of Kirigami folding to create flexible electronic devices from paper and to diversify applications for next-generation sensors, robots and diagnostic devices.

In recent years, there has been growing interest in printed electronics in displays, RFID, and portable devices. Conventional printed electronics based on rigid substrates, such as printed circuit boards, are well known. However, attention has recently turned to soft and flexible shapes, as these features allow bending, twisting, bending or rolling of printed electronics into 3D configurations. In addition to improving the properties of electronic devices, consideration must also be given to reducing environmental impact when developing next-generation printed electronics; factors such as recyclability and toxicity of materials.

To find a candidate who will meet our needs, you don’t have to look far. A team of researchers proposes to use paper as a new medium for printed electronics. Due to its recyclability, degradability, low cost and ease of production, paper is a well suited material for low cost and sustainably printed electronics.

Printing conductive inks, such as nano-silver ink, into electrode patterns on paper is a process commonly used in the manufacture of paper electronics. However, while the paper is flexible, the electrodes printed on it are not, and as the substrate is bent cracks start to form in the electrodes, eventually resulting in fracture. This limitation has severely hampered the development of devices based on paper electronics in various forms.

Today, a team of researchers from Japan and Taiwan are proposing a new solution inspired by Kirigami, the ancient Japanese art of paper cutting, in their recent study published in Physica Status Solidi A – Applications and Materials Science. “Rather than bending nano-silver electrodes, which causes ruptures, we observed that these electrodes could be twisted without fracture in our preliminary experiments. This made us wonder if there was a way to take advantage of this distortion, ”says Dr. Tilo H. Yang of National Taiwan University, who is the lead author of the article. “Then we used the Kirigami, cutting along the fold edge of the paper so that the region near the fold edge could be twisted when the paper substrate is folded. ”

The team found that the structural integrity of conductive nano-silver electrodes and the electrical performance of paper electronics could be well maintained using the Kirigami method. “The electrical resistance of the Kirigami electrode increased by 30% when the paper substrate was fully bent and the conductivity was still maintained after full bending for more than 100 cycles,” says Yang. “The electrodes without the Kirigami structure, on the other hand, disconnected under normal bending.”

The team further demonstrated that the Kirigami method can be used to create multiple mechatronic devices, such as a sensor and a mobile robot, implying that endowing paper electronics with more advanced functionality is on the horizon. “For example, if we bend a few nano-silver electrodes to align them with each other and air is sandwiched between the two, the whole structure functions as an electrostatic capacitor which can be used to measure the angle of bending or to generate electrostatic actuation, “says Professor Jun Shintake of the University of Electro-communications.

The Kirigami strategy provided by the team is expected to bring various applications in sensors and actuators, microfluidic systems, soft robots, and diagnostic devices. These future paper electronics will have more complicated 3D architectures and advanced distributed functions depending on how you imagine and design them.

Reference: T. Yang, et al. “Foldable Kirigami paper electronics”, Physica Status Solidi A – Applications and Materials Science (2020). DOI: 10.1002 / pssa.201900891


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