Materials and Fabrication Techniques to Improve in Stretchability of Transparent Organic Electrochemical Transistors

Highly transparent and flexible electronics enable multimodal sensing that simultaneously measures electrical, optical, and ionic signals. In this study, fully transparent and intrinsically stretchable organic electrochemical transistors (OECTs) are developed using silver nanowires (AgNWs) and semiconducting polymer-based materials on an elastomer substrate. The OECTs exhibit high durability under 100% strain and an optical transparency exceeding 85%. In addition, the investigation of additives in the channel material shows the potential to improve transistor characteristics under high strain. These devices contribute to the development of next-generation, multimodal, healthcare sensors.<br/><br/>Data obtained from the long-term monitoring of biological signals can be used for the diagnosis, prevention, and treatment of diseases [1]. Flexible electronic devices can measure high-quality biological signals through close contact with biological tissues (such as human skin) and reduce the discomfort of wearing them [2]. OECTs can be used for long-term, biological signals because of their low-voltage operation, mechanical flexibility, and high transconductance [3]. Moreover, highly transparent OECTs have contributed to the advancement of multimodal sensing technologies capable of simultaneous electrical, optical, and ionic measurements. However, conventional OECTs that use materials such as metal thin films lack stretchability and transparency, making them unsuitable for multimodal biosensing.<br/>In this study, transparent and stretchable OECTs are developed using AgNWs and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The nanomaterials are implemented on a transparent elastomer substrate using a printing process to make the device fully transparent and stretchable. Nanomaterials comprising OECTs are protected by lamination techniques, thus reducing potential damage to them. High stretching durability and visible-light transmittance are achieved using AgNWs with controlled orientations as wiring materials [4]. The channel materials are patterned onto the substrate using a printing process similar to that used for AgNWs to construct a transparent and stretchable OECTs. Additives to the channel material are optimized by evaluation of the transmission characteristics and frequency response under high strain. On investigation under high strain, additives in the channel material exhibits potential for transistor-characteristics improvement. Therefore, a fully transparent and stretchable sensor suitable for multimodal sensing using electrical, optical, and ionic methods is expected to address requirement for biosensing.<br/><br/><br/>References<br/>[1] T. R. Ray et al., Adv. Mater., 2021, 34, 2107902<br/>[2] Y. Qiao et al., Adv. Mater., 2020, 32, 1901924<br/>[3] J. Rivnay et al., Nat. Rev. Matt., 2018, 3, 17086<br/>[4] A. Takemoto et al., Adv. Sci., 2022, 10, 2204746