Durability Study of Thermal Transfer Printed Textile Electrodes for Wearable Electronic Applications

Abstract

Textile-based electronics hold great promise because they can endow wearable devices with soft and comfortable characteristics. However, the inherent porosity and fluffiness of fabrics result in high surface roughness, which presents great challenges in the manufacture of high-performance fabric electrodes. In this work, we propose a thermal transfer printing method to address the above challenges, in which electrodes or circuits of silver flake/thermoplastic polyurethane (TPU) composites are prefabricated on a release film by coating and laser engraving and then laminated by hot-pressing to a variety of fabrics and textiles. This universal and scalable production technique enables fabric electrodes to be made without compromising the original wearability, washability, and stretchability of textiles. The prepared fabric electrodes exhibit high conductivity (5.48 × 104 S/cm), high adhesion (≥1750 N/m), good abrasion/washing resistance, high patterning resolution (∼40 μm), and good electromechanical performance up to 50% strain. To demonstrate the potential applications, we developed textile-based radio frequency identification (RFID) tags for remote identification and a large-sized heater for wearable thermotherapy. More importantly, the solvent-free thermal transfer printing technology developed in this paper enables people to DIY interesting flexible electronics on clothes with daily tools, which can promote the commercial application of smart textile-based electronics.

Thermally Laminated Lighting Textile for Wearable Displays with High Durability

“…First, the bottom electrode must be stretchable and waterproof. In the authors’ group, the stretchable fabric electrode has previously been manufactured by hot-press lamination using TPU as the binding matrix (Figure S2a), achieving high conductivity, high adhesion, and good abrasion/washing resistance . In the present work, the fabric electrode is used as the bottom electrode for assembling the ACEL device.…”

“…This variation is acceptable for the ACEL device because its operation is not sensitive to small change of resistance in electrodes. Detailed information about the elastic fabric electrode is referred to the author’s previously published work …”

“…As reported in our previous work, the as-prepared Ag flakes/TPU conductive paste was blade coated on the silicone oil treated side of the PET release film and then put into an electrothermal constant temperature dryer (DHG-9036A, Shanghai Jinghong Experimental Equipment Co., LTD) for drying at 80 °C for 2 h. After the conductive film was thoroughly dried, the HMA solution was blade coated onto its surface with a coater (TD-5000GJ) and then dried at 80 °C for 2 h to obtain the HMA layer. The as-prepared bilayer film will be laminated onto the fabric by hot pressing as the bottom electrode of the ACEL device.…”

“…In the author’s group, ACEL devices have been fabricated on elastic fabrics by using a layer-by-layer screen printing process, achieving high brightness and excellent durability . For successful printing of functional materials on fabric, surface planarization is necessary because of the porous nature of fabrics, which complicates the manufacturing process. , Moreover, the functional materials have to be mixed with various organic solvents in order to be printable, which not only corrode the fabrics but also leave residues, causing issues to meet the clothing application standards. , …”

Highly Conductive and Compliant Silver Nanowire Nanocomposites by Direct Spray Deposition

“…Stretchable electronics further allow conformal attachment to soft biological tissues and skins, thereby enabling emerging applications in wearable health monitoring, , human–machine interfaces, − and advanced prosthetics. , Compliant conductors represent the key building materials for flexible and stretchable electronics to construct active electrodes and electronic interconnects. − A straightforward approach utilizes conventional rigid metals to create highly deformable structures by introducing buckling designs, serpentine patterns, , and Kirigami cuts. , The inherently high stiffness of these materials presents a practical challenge for the reliable operations of corresponding devices due to the large mechanical mismatch with other soft components. Alternatively, intrinsically compliant conductors are created by dispersing various conductive nanostructures into elastomer matrices including carbon nanotubes, , metal nanowires, − metal nanoflakes, − and metal nanodendrites. , In these nanocomposites, the three-dimensional percolation network of conductive nanofillers is the enabler of high electrical conductivity and excellent mechanical deformability, thereby providing the basis for the scalable fabrication of soft devices and systems …”