Programmable Assembly of Hierarchical 3D Aerogel.

3D porous ordered aerogels attract considerable attention in catalysis, energy storage, and biomedical engineering, yet the precise construction of aerogels' microstructures remains challenging. Herein, inspired by secondary dendrite formation in metal casting, a programmable assembly strategy is reported to customize 3D hierarchical ordered aerogels through freeze casting with internal cold fingers (ICF). As revealed by the temperature field and phase-transition simulations, the ICF effectively regulates the temperature gradient, which subsequently controls the nucleation process, and growth orientation of ice crystals during the solidification of the ice template. As a result, programmable regulation of the porous graphene oxide aerogels is attained. Benefiting from the hierarchical ordered structures, 3D porous ordered reduced graphene oxide aerogels exhibit significant heat dissipation enhancement in microelectronic devices than conventional freeze casting aerogels'. Furthermore, the freeze casting employing the ICF strategy provides a universal strategy to construct programmable 3D porous aerogels of MXene nanosheets, h-BN nanosheets and carboxymethyl cellulose nanowires.