Additive manufacturing of solid-state ion conductors opens the possibility to fabricate at low-cost novel electrochemical devices as an alternative to clean room techniques. This would promote their use for small-scale production or rapid prototyping. Memristive devices based on conductive bridging are a promising technology for next generation memories, neuromorphic computing, and reconfigurable electronic switches.^1,2 Electrochemically driven growth of a metal filament from the cathode to the anode through a solid-state ionic conductor is used to switch the device from a low conductivity state to a high conductivity state. They are of particular interest in satellite electronics due to their innate radiation hardness compared to traditional transistor-based devices.

We have printed Pt/AgI/Ag electrochemical cells (Figure 1(a), inset) as a proof of concept that such devices can be produced by additive manufacturing. The AgI electrolyte is deposited by computer controlled extrusion of a paste and the electrodes are formed by initially by vapor deposition and subsequently by inkjet printing. The latter demonstrates a completely additively manufactured device. During filament formation AgI acts as an Ag⁺ ion conductor, Pt is the cathode, and Ag is the anode. The current of the device at a fixed applied voltage is found to increase by three orders of magnitude (Figure 1(a)) as the conductive bridging is completed. Cyclic voltammetry was also able to demonstrate reversible switching between the high and low conductivity states (Figure 1(b)). Finally, impedance measurements were performed to evaluate the conductivity of the printed AgI electrolyte as a function of temperature.

References

1. I. Valov and M. N. Kozicki, J. Phys. D. Appl. Phys., 46, 74005 (2013).
2. A. H. Edwards, H. J. Barnaby, K. A. Campbell, M. N. Kozicki, W. Liu, M. J. Marinella, Proc. IEEE, 103, 1004–1033 (2015).

Figure 1 (a) Resistance decreases three orders of magnitude during filament formation when bridging is complete at point X. A schematic of the cell is provided in the inset. and (b) Reversible switching between a high resistance state and a low resistance state by cyclic voltammetry with a Pt/AgI/Ag cell.