Flexible Organic Electrochemical Memory on 2µm-Thick Ultrathin Substrate and Bio-Signal Processing

A neuromorphic device (NMD) enables low-energy and highly efficient computation of large amounts of data as a non-von Neumann computing device. Here, NMD is described in organic electrochemical memories (OECMs) fabricated on an ultrathin substrate and their stable electrical performance under mechanical deformation. The flexible OECMs have increased the potential for biocompatibility of a wearable device integrated to detect and predict diseases during daily life.<br/>Previously, NMD with versatile materials fabricated using memristors has performed low energy consumption and conducted efficient operations [1]. The performance of NMD has been grown and being revealed on the importance of the higher linear conductance change contributing on the higher calculation accuracy [2]. In addition, mechanical durability in the operation of NMD is attractive to realize high intelligence wearable devices involving human movements and reduce discomfort during long-term wear [3-5].<br/>In this study, flexible OECMs are fabricated by layering metals, conductive polymers, all-solid-state electrolytes, and 2 µm-thick ultrathin substrates. The conditions of the linear conductance change in OECMs have been found by comprehensively assessment on the time constants of the peripheral circuits including the OECM. As a result, the memory value changes of up to 9 bits can be identified by ensuring the conductance linearity. The freestanding electrolyte gel is fabricated by mixing two polymers and exhibits high conductivity (1.6 S/m) similar to liquid electrolytes. Moreover, OECMs using the electrolyte gel operate stably even under bending deformation (bending radius 0.75 mm) and enable recording arrhythmia of pseudo electrocardiograms. Thus, the pathognomonic signal detection with developed flexible OECMs has stepped forward to realize an intelligent wearable device.<br/><br/>[1] Modha DS et al., Science. 382, 329-335 (2023).<br/>[2] Zhang, W et al., Nat Electron. 3, 317-382 (2020).<br/>[3] Y. Burgt et al., Nat Mater. 16, 414-418 (2017).<br/>[4] T. Araki et al., Adv Mater. 32, 1902684 (2020).<br/>[5] A. Takemoto et al., Adv Sci. 10, 2204746 (2023).