Porosity-Tunable Structures with "Fossilized" Bubbles

Porous structures have garnered increasing attention in recent research on lightweight, multifunctional materials that enable a wide range of applications including separation, adsorption, sensing, pervaporation, and reactions. Here we report a versatile method for creating noninterconnected, porous structures with tunable pore size distributions by "fossilizing" bubbles in the curing matrix. The bubbles are generated from a pressure-driven flow of air/vapor through a template with micrometer-scaled channels. Tunable fabrication of porous materials with adjustable pore size and pore distribution can be achieved by controlling the pressure difference and the templates' design. To quantitatively guide the synthesis of the porous structures, we develop a theoretical model to predict the pore size, which agrees with experiments. Moreover, by maneuvering the pore size distributions of this structure on demand, we demonstrate its feasibility as a differential thermal insulator that can be utilized in various fields such as microfluidic chips and microreactors. Overall, this facile method provides a strategy for fabricating lightweight porous structures that have broad applications in microfluidics, thermal insulation, separation science, and tissue engineering.