Fabric-based piezoelectric energy harvester developed

Researchers from the Korea Advanced Institute of Science and Technology (KAIST) have developed a highly flexible yet sturdy wearable piezoelectric harvester using the simple fabrication process of hot pressing and tape casting. Featuring high interfacial adhesion strength, the team’s energy harvester should bring us one step closer to being able to manufacture embedded wearable electronics.

Wearable devices are increasingly being used in a wide array of applications, from small electronics to embedded devices such as sensors, actuators, displays and energy harvesters. But despite their many advantages, high costs and complex fabrication processes remain challenges that prevent wearable devices from reaching commercialisation. In addition, their durability is frequently questioned.

To address these issues, KAIST researchers led by Professor Seungbum Hong developed a new fabrication process and analysis technology for testing the mechanical properties of affordable wearable devices. The team said the novelty of their technology, published in the journal Nano Energy and patented in Korea last year, lies in its simplicity, applicability and durability.

The research team used a hot pressing and tape casting procedure to connect the fabric structures of polyester and a polymer film. Hot pressing is usually used when making batteries and fuel cells, due to its high adhesiveness, and takes only 2–3 min. This enables the direct application of a device into general garments, just as graphic patches can be attached to garments using a heat press. In particular, when the polymer film is hot pressed onto a fabric below its crystallisation temperature, it transforms into an amorphous state. In this state, it compactly attaches to the concave surface of the fabric and infiltrates into the gaps between the transverse wefts and longitudinal warps.

The team’s surface and interfacial cutting analysis system (SAICAS) proved the high mechanical durability of the fabric-based wearable device by measuring the high interfacial adhesion strength between the fabric and the polymer film. The system is more precise than conventional methods (peel test, tape test and microstretch test) because it qualitatively and quantitatively measures the adhesion strength. The team first used the SAICAS in the field of wearable electronics to test the mechanical properties of polymer-based wearable devices.

“This study could enable the commercialisation of highly durable wearable devices based on the analysis of their interfacial adhesion strength,” Prof Hong said. “Our study lays a new foundation for the manufacturing process and analysis of other devices using fabrics and polymers. We look forward to fabric-based wearable electronics hitting the market very soon.”

Image courtesy of the study authors.

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