3D printing of metallic microarchitectures with controlled internal structures is realized at room temperature in ambient air conditions by the manipulation of metal ion concentration and pulsed electric potentials in the electrolyte meniscus during the meniscus-guided electrodeposition. Precise control of the printing nozzle enables the drawing of complex 3D microarchitectures with well-defined geometries and positions.

Moving printed electronics to three dimensions essentially requires advanced additive manufacturing techniques yielding multifunctionality materials and high spatial resolution. Here, we report the meniscus-guided 3D printing of highly conductive multiwall carbon nanotube (MWNT) microarchitectures that exploit rapid solidification of a fluid ink meniscus formed by pulling a micronozzle. To achieve high-quality printing with continuous ink flow through a confined nozzle geometry, that is, without agglomeration and nozzle clogging, we design a polyvinylpyrrolidone-wrapped MWNT ink with uniform dispersion and appropriate rheological properties. The developed technique can produce various desired 3D microstructures, with a high MWNT concentration of up to 75 wt % being obtained via post-thermal treatment. Successful demonstrations of electronic components such as sensing transducers, emitters, and radio frequency inductors are also described herein. We expect that the technique presented in this study will facilitate selection of diverse materials in 3D printing and enhance the freedom of integration for advanced conceptual devices.

Organic-inorganic metal halide perovskites, particularly CH 3 NH 3 PbX 3 (X = Cl, Br, and I), have recently emerged as a promising optoelectronic material [1] because of their excellent properties such as large optical absorption, long carrier diffusion length, high carrier mobility, and low-cost solution production process. [2][3][4][5][6] Over the past decade, there have been conducted substantial research to utilize perovskites for diverse applications as solar cells, [2,7,8] photodetectors, [9,10] light emitting diodes, [11,12] and lasers. [13,14] Most of the research has focused on the control over crystallinity or chemical composition in a thin film form, in result, making great advances in material performance. [15][16][17][18][19] Continuous demands on optoelectronic devices with high integration density and new functions have raised the need for nanostructured perovskites. [20] Especially, nanowires, 1D nanostructures with controlled diameters and lengths, are the basic building blocks for creating miniaturized devices. Techniques to fabricate perovskite nanowires mainly rely on i) vapor-phase deposition [21,22] or ii) solution-mediated crystallization. [14,[23][24][25][26] The former offers an excellent crystal quality but lacks the ability to precisely position individual nanowires. In the latter that is based on supersaturation of solutes, there have been several remarkable attempts to fabricate and align individual nanowires by confinement of solution inside templates, [23,24] nanoimprint molds, [25] or nanofluidic channels [26] under evaporation of solvent.Recently, some clever methods based on inkjet printing have been devised for patterning perovskite micro/nanostructures. [27,28] These attempts have enhanced the freedom of nanostructures design beyond straight nanowires, potentially enabling a high-level integration of perovskite circuitries and devices. However, the developed patterning techniques for perovskites are still limited to in-plane fabrication and alignment.Since its invention in the 1980s, 3D printing, known as additive manufacturing, has attracted great attention as a facile method to produce tangible freeform structures. Beyond simple prototyping, there have recently been enormous efforts to improve or diversify the properties of 3D printed objects-for their practical use-by engineering materials' crystallinity [29,30] or molecular orientation. [31][32][33] In this context, owing to their As competing with the established silicon technology, organic-inorganic metal halide perovskites are continually gaining ground in optoelectronics due to their excellent material properties and low-cost production. The ability to have control over their shape, as well as composition and crystallinity, is indispensable for practical materialization. Many sophisticated nanofabrication methods have been devised to shape perovskites; however, they are still limited to in-plane, low-aspect-ratio, and simple forms. This is in stark contrast with the demands of modern optoelectronics with freeform circui...