3D Printing of Hierarchical Porous Silica and α‐Quartz

Abstract

The ability to macroscopically shape highly porous oxide materials while concomitantly tailoring the porous network structure as desired by simple and environmentally friendly processes is of great importance in many fields. Here, a purely aqueous printing process toward deliberately shaped, hierarchically organized amorphous silica and the corresponding polycrystalline quartz analogues based on a direct ink writing process (DIW) is presented. The key to success is the careful development of the sol–gel ink, which is based on an acidic aqueous sol of a glycolated silane and structure‐directing agents. The resulting 3D (DIW) printed silica consists of a macroporous network of struts comprising hexagonally arranged mesopores on a 2D hexagonal lattice. Together with a printed porous superstructure on the millimeter scale, well‐defined pore sizes and shapes on at least three hierarchy levels can thus be fabricated. The introduction of devitrifying agents in the printed green part and subsequent heat treatment allows for the transformation of the silica structure into polycrystalline α‐quartz. While small pores (micro‐ and mesopores below 10 nm) are lost, the printed morphology and the macroporous network of struts is preserved during crystallization.

Tailoring the crystal growth of quartz on silicon for patterning epitaxial piezoelectric films

“…5 Lately, fundamental and application-driven interest in nanoscale SiO 2 provided new insights towards understanding and controlling silica devitrication in microporous, mesoporous and ultrathin silica. [6][7][8][9][10][11][12][13][14][15] Most of these studies highlight the essential role of alkaline, 11 alkaline earth [8][9][10]15 and transition metal dopants 7 in obtaining the desired crystallization. For instance, the formation of iron silicate seeds underpins the epitaxial growth of thermally evaporated ultrathin silica on Ru (0001).…”

“…For instance, with the presence of amphiphiles the temperature of silica crystallization under high pressure was lower than in the case where the surfactants had been previously removed. 14 In this sense, Putz et al used sodium metasilicate solutions in microemulsions to obtain small a-quartz nanocrystals at room temperature or under mild hydrothermal conditions below 200 C. 15 The above examples illustrate the complexity of controlling the crystallization and microstructure of nanostructured aquartz and highlight the critical roles of the silica porosity, the concentration, distribution and connement of devitrifying agents or the presence of surfactants.…”

Gravure printing for mesoporous film preparation

“…With respect to mesoporous materials, printing is mainly based on paste printing usually to fabricate net-like macroscopic architectures of mesoporous silica, mostly intended to be used for cell growth. 20,21 Thereby ordered mesoporous structures such as hexagonally arranged mesopores have been demonstrated. 20 Only a few studies focus on printing with higher local resolution.…”

“…20,21 Thereby ordered mesoporous structures such as hexagonally arranged mesopores have been demonstrated. 20 Only a few studies focus on printing with higher local resolution. For example, Kotz et al show the possibility to print fused silica 3D structures by using stereolithography.…”

Freeform Microfluidic Networks Encapsulated in Laser‐Printed 3D Macroscale Glass Objects

“…However, fabrication of freeform 3D hollow microchannels in fused silica is still difficult for current 2D fabrication techniques in terms of complex and tedious fabrication procedures, additional costs for aligning, stacking, and bonding steps. [27] Meanwhile, 3D printing of glass materials emerging in recent years brings some new opportunities for scalable fabrication of freeform glass structures by either additive manufacturing strategies [28][29][30][31][32][33] or laser subtractive processing methods. [15][16][17][18][19][20] A suspended hollow microchannel structure with a 3D controllable configuration can be fabricated in a way of either laser-assisted selective wet etching [21][22][23] or liquid-assisted laser ablation.…”