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  • Open Access

Modeling and design of integrated circuits based on ionic bipolar junction transistors

Soichiro Tottori1,2,* and Rohit Karnik1

  • *Contact author: soichiro.tottori.e2@tohoku.ac.jp
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Phys. Rev. Applied 24, 054080 – Published 26 November, 2025

DOI: https://doi.org/10.1103/7r6s-731v

Abstract

Biological systems rely on ions and molecules as information carriers rather than electrons, motivating the development of devices that interface with biochemical systems for sensing, information processing, and actuation via spatiotemporal control of ions and molecules. Iontronics aims to achieve this vision by constructing devices composed of ion-conducting materials such as polyelectrolyte hydrogels, but advancing beyond simple single-stage circuit configurations that operate under steady-state conditions is a challenge. Here, we propose and model more complex ionic circuits, namely bistable flip-flop and ring oscillators, consisting of multiple ionic bipolar junction transistors (IBJTs). We begin by modeling and characterizing single IBJTs using both a simplified one-dimensional Nernst-Planck model and a more-detailed two-dimensional Poisson-Nernst-Planck model, elucidating the effects of geometry, size, and fixed charge on the IBJT performance and response time. The one- and two-dimensional models exhibit good agreement, indicating negligible transverse inhomogeneities. In addition, these models show that reducing the base width improves current amplification, a behavior analogous to electronic bipolar junction transistors. Building on this understanding, by using the IBJTs as voltage inverters and buffers, we design and model more complex ionic circuits that dynamically change their states in response to ionic signals. Specifically, we demonstrate that the ionic flip-flop retains one-bit memory and that the ring oscillator achieves autonomous periodic self-oscillation without an external clock. Our work provides a foundation for designing dynamic iontronic circuitry using ionic conductors, enabling biochemical signal processing and logic operations based on ionic transport.

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Phys. Rev. Applied 24, 054080– Published 26 November, 2025
  • Received 18 July 2025
  • Revised 18 October 2025
  • Accepted 27 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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