Additive‐Free, Gelled Nanoinks as a 3D Printing Toolbox for Hierarchically Structured Bulk Aerogels
Matthias Rebber, Malte Trommler, Irina Lokteva, Samanehalsadat Ehteram, Andreas Schropp, Sandra König, Michael Fröba, Dorota Koziej
Abstract
Abstract Aerogels are highly porous solids that maintain the properties of individual nanomaterials at a macroscopic scale. However, the inability to fabricate hierarchical architectures limits technological implementation in energy storage, gas‐sorption, or catalysis. A 3D‐printing methodology for additive‐free TiO 2 nanoparticle‐based aerogels is presented with full control of the nano‐, micro‐, and macroscopic length‐scales. To compensate for ink's low solid loading of 4.0 vol% and to enable subsequent processing into aerogels via supercritical drying, the printing is done in a liquid bath of alkaline p H. The 3D‐printing protocol retains a high specific surface area of 539 m 2 g –1 and a mesopore diameter of 20 nm of conventionally casted aerogels while offering an unparalleled designability on the micrometer scale. To illustrate the new geometric freedom of 3D‐printed aerogels, the microstructure of a strongly light‐absorbing, photothermal Au‐nanorod/TiO 2 aerogel is defined. To date, photothermal nanomaterials are mainly applied in the form of unstructured films where scalability is limited by light attenuation. Microstructures in 3D enhance light penetration by a factor of four and facilitate spatially defined heating on a macroscopic scale. The process can be generalized for a broad material library and allows to design inks with specific functionality, thus making aerogels adaptable for their target application.