Professor Seungbeom Hong's research team at KAIST's Department of Materials Science and Engineering
Combination of conductive fabric and piezoelectric polymer film
Development of a method for manufacturing a wearable energy harvester


Today, wearable devices are used in a wide range of applications, from sensors and motors to displays and energy harvesting. Furthermore, they are rapidly evolving from miniaturization to embedded form factors. Accordingly, wearable devices based on comfortable and durable fabrics that can be embedded in existing clothing are attracting attention.

The Korea Advanced Institute of Science and Technology (KAIST) announced on the 9th that a research team led by Professor Seung-Beom Hong of the Department of Materials Science and Engineering has successfully developed a method for manufacturing a fabric-based wearable piezoelectric energy harvester that is cost-competitive and highly durable using a hot pressing method.

Hot pressing is a method of firmly bonding two objects by applying temperature and pressure, and piezoelectric energy harvesting is a technology that converts energy such as pressure and vibration into usable electrical energy using piezoelectric materials.

Existing fabric-based wearable devices have yet to reach the practical stage due to limitations in terms of process and cost, stemming from complex manufacturing methods and equipment requirements. Furthermore, the lack of bonding and efficiency testing between the fabric within the device and the actual operating components raises questions about the device's durability.

To address these issues, active research is being conducted on simple, inexpensive processes and materials, as well as new mechanical property analysis technologies. The research team developed a method for manufacturing a fabric-based wearable piezoelectric energy harvester by combining a conductive polyester fabric and a piezoelectric polymer film (P(VDF-TrFE)) using hot pressing.

Hot pressing is a method primarily used in the production of batteries and fuel cell cells. It is a fast and simple process that can be completed in 2 to 3 minutes while also achieving high adhesive strength.

When a polymer film is bonded to a fabric at a temperature near or below the crystallization temperature, the polymer film surface becomes amorphous, densely bonding to the rough fabric surface with a wide contact area, and leaks between the warp and weft yarns to form nails, allowing for high interfacial bonding.

Wearable devices developed using the hot pressing method are expected to have the potential to be applied to existing clothing, thereby reducing the process cost.

In addition, the mechanical durability of the wearable device was proven by measuring the interfacial adhesion between the fabric and the polymer film using the newly introduced 'Surface and Interfacial Cutting Analysis System (SAICAS)' in addition to the existing durability test method, the bending test.

Interfacial bonding using SAICASAdhesion analysis is a method that quantitatively and qualitatively measures force at the microscale using a blade. It is more accurate than existing methods for measuring interfacial adhesion, such as peel tests, tape tests, and microstretch tests. The research team stated, "Interfacial adhesion analysis using SAICAS could be used as a new method for testing the durability of wearable devices using polymers in the future."

Professor Hong Seung-beom commented, “The fabric-based wearable piezoelectric energy harvester manufacturing technology developed this time has increased the possibility of commercializing fabric-based devices,” and “Through analysis of interfacial adhesion, it has suggested a design direction for high-durability wearable devices.”

Meanwhile, this research was patented domestically on December 23rd of last year, and was published in the September 2020 issue of the international academic journal 'Nano Energy', and was published online on May 22nd. The research was participated by the research team of Professor Noh Kwang-soo of the Department of Materials Science and Engineering at the same university, Professor Yoo Seung-hwa of the Department of Mechanical Engineering, and Professor Lee Yong-min of the Department of Energy Engineering at DGIST.