Isolated Mesoporous Microstructures Prepared by Stress Localization-Induced Crack Manipulation.

Cracks observed in brittle materials are mostly regarded as defects or failures. However, they can be a valuable tool when implemented in a controlled way. Here, we introduce a strategy to control the crack propagation of mesoporous micro-patterns (prisms and pyramids), which leads to the isolation of well-defined micro-structures. Mesoporous micro-patterns were fabricated by the soft imprinting technique with wet TiO2 nanoparticle (NP) pastes, followed by sintering to remove organic components. Since the volume of the paste significantly shrinks during the sintering step, stress is localized at the edge of micro-patterns, in good agreement with the FEM simulations, creating well-defined cracks and their propagation. It was demonstrated that the degree of stress localization is determined by the thickness of residual layers, NP size, and the heating rate. After controlled crack propagation and delamination of micro-particles from the substrates, mesoporous micro-wires and micro-particles were successfully produced and functionalized from the isolated mesoporous prisms and pyramids. The method proposed in this study for controlled crack manipulation and delamination opens a door for straightforward and economical fabrication of well-defined mesoporous micro-particles.