3D printed colloidal aerogels: Principle, process, performance, and perspective

Aerogels is a kind of pivotal porous nano-materials mushroomed in multiple disciplines, involving but not limited to material science, sol–gel chemistry, physics and biology, due to their tremendous systems and exotic properties. 3D printing techniques further endow aerogels with customized macroscopic geometries, designed hierarchical structures, and integrated complex components, which means that the controllable structure closely associated with performance and application is easy to achieve. However, although abundant achievements have been made so far, systemic overview on 3D printed aerogels is still on its early stage. In this review, a term of “colloidal aerogels” is emphasized to describe those aerogels prepared from nanoscale building blocks as the starting materials by using dispersion-stabilization-destabilization processes, and the theme of “3D printed colloidal aerogels together with their state-of-art progress” is summarized in depth from a colloidal science perspective for the first time, including the developed timeline, key procedures, printing strategies, the classification, the confining functionalization, fascinating properties and emerging applications, as well as current challenges and future opportunities. In especial, the thermodynamics/kinetics during printing, sol/sol–gel/gel printing strategies, and confining functionalization are elaborately introduced. Therefore, it can be expected that this review might breathe new life into the development of 3D printed colloidal aerogels.