Isolated Mesoporous Microstructures Prepared by Stress Localization-Induced Crack Manipulation

Abstract

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 micropatterns (prisms and pyramids), which leads to the isolation of well-defined microstructures. Mesoporous micropatterns were fabricated by the soft imprinting technique with wet TiO 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 micropatterns, in good agreement with finite element method 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 heating rate. After controlled crack propagation and delamination of microparticles from the substrates, mesoporous microwires and microparticles 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 microparticles.

Stamp-Perforation-Inspired Micronotch for Selectively Tearing Fiber-Bridged Carbon Nanotube Thin Films and Its Applications for Strain Classification

“…Therefore, many research groups tried to develop various crack-controlling methods to better understand cracking mechanisms and thus to solve this issue. − Utilizing fast crack-propagation features with proper notch structures, , the cracking behavior has been somewhat controlled in brittle materials. Based on the studied methods, several applications such as micro- and nanofludic channel formation, biological applications, material synthesis, , and tactile or strain sensors − have been reported. However, there are still limitations in predesigning position and controlling size, propagation, and density of cracks.…”

“…Laser ablation or photolithography method has been used for dense in-plane notch formation, , but such methods are costly and material dependent. For dense out-of-plane notches, the polymer mold method has been used, but it also showed limitation in fully controlling the cracking phenomenon including cracking termination at predesigned positions in ductile materials. , …”

“…For dense out-ofplane notches, the polymer mold method has been used, but it also showed limitation in fully controlling the cracking phenomenon including cracking termination at predesigned positions in ductile materials. 9,16 Here, we show a stamp-perforation-inspired cracking mechanism in a very ductile material, carbon nanotube (CNT) thin film, by using inkjet-printed out-of-plane notch architectures. L-shape micronotch (LMN) patterns effectively localize the high strain and initiate crack formation around them.…”

General Strategy to Optimize Gas Evolution Reaction via Assembled Striped-Pattern Superlattices

“…The corresponding current density on the Pt NP films decreased rapidly after 7 h, until it equalized the current of the blank electrodes after 9 h. This signifies that the film dissolved completely, as shown in Figures b and S10b. Gas evolution reactions most probably caused the mechanical performance of the catalyst films to degrade due to the initiation of cracks, which then developed further. − There are two main reasons for the superior durability of the Pt SP 5 pattern. First, the stress on the Pt SP 5 electrode was weak because of the small size of the air bubbles produced by Pt SP 5 relative to those induced by the Pt NP films.…”

Tailoring 3D shapes of polyhedral milliparticles by adjusting orthogonal projection in a microfluidic channel

“…20 To date, numerous investigations have been conducted for PMPs synthesis. Surface-tension-induced selffolding, 23,24 mold casting, 25,26 nanoparticles selfassembly, 27,28 and two-photon lithography 29 have been developed for fabricating the PMPs with a variety of shapes such as tetrahedron, pyramid, octahedron, cube, and so forth. However, the shape fidelity, size precision, and surface quality of the obtained PMPs are still limited.…”