Femtoliter Meniscus-Guided Crystallization for 3D Printing

Abstract

3D printing, one of the most disruptive technologies to emerge in recent years, has attracted increasing attention due to its potential impact on science, industry, and society. Winning high-quality materials is one of the most important challenges in modern 3D printing technology. To this end, beyond exterior shaping, 3D printing techniques that can also engineer crystallinity or molecular orientation are in a great demand. Here, we have developed a new method to incorporate solution-mediated crystallization into nanoscale 3D printing. The key idea is to exploit a femtoliter solution meniscus formed on a nanopipette to guide evaporation-induced crystallization in mid-air. Evaporative loss of solvent rapidly creates a supersaturated concentration field of solutes inside the femtoliter meniscus, leading to the nucleation and growth of nanocrystals. Furthermore, omnidirectional guiding of the meniscus with moving the nanopipette realizes freeform 3D nanostructures with excellent crystallinity. By employing this method, we have successfully demonstrated nanoscale 3D printing of two promising material systems: (1) organic-inorganic metal halide perovskites and (2) self-assembled peptides. In this talk, we will present the theoretical and experimental results including examples of 3D printed crystalline structures and discuss prospects of our work for potential applications in electronics and optoelectronics.