A nonlinear framework for deformable ionic conductor fibers with variable cross-sections: Application to mechanically regulated ionic junctions

Deformable ionic conductors combine mechanical stretchability with ionic conductivity, enabling broad applications in sensing, actuation, and energy harvesting. In this study, we propose an ionic junction with a variable cross-section, where the ion transport behavior can be regulated by applying tensile or compressive loads. This effect arises from the intrinsic electro-chemo-elastic coupling of these materials. To capture this mechanism, we developed a one-dimensional framework incorporating constitutive nonlinearity and solved it efficiently using the differential quadrature method. The results show that the ionic junction exhibits unidirectional conductivity, and its ionic current-voltage characteristics can be modulated by mechanical loading. Through variable cross-section design, the axial stress gradient within the fiber influences the distribution of electrochemical potential, thereby affecting ion transport behavior. We further analyzed the influence of different cross-sectional functions on the degree of regulation, and the analysis reveals that steeper changes in cross-sectional area along the axis lead to stronger mechanical modulation. The model and findings presented in this paper provide a foundation for the development of intelligent ionic devices.