Myelin surfactant assemblies shaping the electrodeposition of copper dendrites.

Abstract

Self-organization of inorganic matter enables bottom-up construction of materials with targetted shapes suited to their function. Positioning the building blocks in the growth process involves a well-balanced interplay of reaction and diffusion. Whereas (supra)molecular structures have been used to template such growth processes, we reasoned that molecular assemblies can be employed to actively create concentration gradients which shape the deposition of solid, wire-like structures. The core of our approach comprises the interaction between myelin assemblies that deliver copper(II) ions to the tips of copper dendrites, which in turn grow along the Cu2+-gradient upon electrodeposition. First, we successfully include Cu2+ ions amongst amphiphile bilayers in myelin filaments, which grow from C12E3-based source droplets over air-water interfaces. Second, we characterize the growth of dendritic copper structures upon electrodeposition from a negative electrode at the sub-mM Cu2+ concentrations that are anticipated upon release from the copper loaded myelins. Third, we assess the intricate growth of copper dendrites upon electrodeposition, when combined with copper loaded myelins. The myelins deliver Cu2+ at a negative electrode, feeding copper dendrite growth upon electrodeposition. Intriguingly, the copper dendrites follow the Cu2+ gradient towards the myelins, and grow along them towards the source droplet. We demonstrate the growth of dynamic connections amongst electrodes and surfactant droplets in reconfigurabe setups – featuring a unique interplay between molecular assemblies and inorganic, solid structures. With the growing interest in neuromorphic circuitry, we envision such a self-organizing system opening entirely new pathways for interconnected networks of (semi)conductive wires that are integrated with soft-matter based systems.