Direct Inkjet 3D Printing Microwires with Small Feature Size by Freezing, Sublimation, and Evaporation Induced Colloidal Nanoparticles Self‐Assembly Mechanism

Abstract The feature size (FS) of inkjet printing is limited by nozzle size and drop spreading, which limits the realization of small optoelectronics devices and 3D microstructures. Some methods can realize small FS, but sacrifice advantages of inkjet technology. For instance, dewetting can reduce FS with all the advantages of inkjet technology kept, but is hard to print wires due to Rayleigh–Plateau instability. To solve these problems, in this paper, freezing and sublimation are introduced to direct inkjet printing wire processes. After optimizing the glycerol amount and adding tert‐butyl alcohol (TBA) in water‐based nanoparticle inks, condensed microwires of PS colloidal nanoparticles, graphene oxide (GO) nanosheets, and silver nanowires (AgNws) with small FS can be printed, respectively, by freezing, sublimation, and evaporation induced nanoparticle self‐assembly (FSE‐INS) mechanism. Using printhead with the nozzle size of 21 µm, the minimum feature size is only ≈2 µm for GO nanosheet samples. The FSE‐INS mechanism shows particle‐dimension dependent structure properties, introduces an additional particle manipulation freedom perpendicular to the substrate with sacrificial vertical solid surfaces, and exhibits great potential to realize small and novel devices and 3D structures, without sacrificing the advantages of inkjet technology.