[13p-1G-1~7] Seeds Researches in Organic Electronics

△ [13p-1G-2] Processing of free-standing conductive polymer nanofilms for application as skin-contact electrodes

〇(D)Kento Yamagishi¹, Toshinori Fujie¹, Shinji Takeoka¹ (1.Grad. Sch. Adv. Sci. Eng., Waseda Univ.)

Keywords:PEDOT:PSS,conductive polymer,wearable

Development of wearable electronic devices has provided a tremendous improvement for advanced healthcare. For a long, real-time, and unperceivable personal health monitoring, such devices should be more small/thin, flexible, skin-conformable, biocompatible, and stable/durable. Recently, sheet-like skin-contact electronic devices such as epidermal electronics (J. A. Rogers et al., Science, 333, 838 (2011)) have been widely reported in the field of flexible electronics. However, there has not been established a technology for cost-effective scalable preparation of skin-applicable electronic materials with high flexibility, adhesiveness, and conformability. A free-standing ultrathin polymer film (referred to as “polymer nanosheet”) has unique physical properties such as physical adhesion and flexibility due to its huge size-aspect ratio. Thus, integration of conductive property into the nanosheets may generate electronic soft-nanomaterials with higher flexibility, adhesiveness, and conformability compared to other flexible skin-contact electronics. To this end, we constructed conductive polymer nanosheets comprised of one of the most widely used conductive polymers, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), which is commercially available as an aqueous dispersion named “Clevios^TM PH1000” from Heraeus Co., Ltd. We have established a scalable fabrication (10 cm x ~20 m) of the nanosheets by a roll-to-roll process using a micro gravure coater (A. Zucca, K. Yamagishi et al., J. Mater. Chem. C, 3, 6539 (2015)). Conductivity of the PEDOT:PSS nanosheets was enhanced (~500 S/cm) with the addition of several biocompatible plasticizers as secondary dopant. The prepared bilayered conductive nanosheets; PEDOT:PSS nanosheets supported by another nanosheet comprised of several polymers such as polylactides (PLA), polystyrene (PS), and elastomers (total thickness: 200-300 nm), were collected as a free-standing state from substrates by facile handling and showed good adhesiveness and conformability to human skin without using any chemical and biological glue. Such conductive nanosheets were mechanically and electrically stable on the human skin surface against flexion movement and body sweating. We also demonstrated the efficiency of the conductive nanosheets as skin-contact electrodes, which successfully detected surface electromyography from a healthy subject with as high a signal-to-noise ratio as conventional pre-gelled electrodes. Finally, towards real-world application such as sports-medical use, we evaluated the stability of the nanosheets on the skin against vigorous exercise under hot and humid condition.