A hundred times faster: Novel, rapid sol-gel synthesis of bio-glass nanopowders (Si-Na-Ca-P system, Ca:P = 1.67) without aging Abstract Synthesis of sol-gel glass with incorporation of Na 2 O is extremely difficult, as such glasses have a great tendency to crystallize. Slow drying and aging over several days or weeks is usually required in sol-gel preparation procedures. This work reports a fast, novel route for the synthesis of bioglass powders in a considerably shortened period of 1 h. A comparative study of sol-gel derived glasses made by this novel route using rotary evaporator drying, and a conventional route using oven drying and aging, revealed that the two methods produce stabilized (devitrified) bio-glasses with virtually identical behavior and properties. Indeed, the rapidly dried powder exhibited slightly enhanced properties that should result in improved bioactivity. Fourier-transform infrared spectroscopy was used to understand the structures of the synthesized powders, and MAS-NMR was used to look at the degree of polymerization. This innovative, rapid route was successfully demonstrated to produce glass and devitrified glass nanopowders more than one hundred times quicker than the quickest reported standard drying methods.

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This article reports the first robocasting of a sol-gel based glass ceramic scaffold. Sol-gel bioactive glass powders usually exhibit high volume fractions of meso-and micro-porosities, bad for colloidal processing as this adsorbs significant portion of the dispersing medium, affecting dispersion and flow. We circumvent these practical difficulties, to achieve pastes with particle size distributions, high solids loading and appropriate rheological properties for extrusion through fine nozzles for robocasting. Scaffolds with different macro-pore sizes (300-500 μm) with solid loadings up to 40 vol.% were robocast. The sintered (800°C, 2 h) scaffolds exhibited compressive strength of 2.5-4.8 MPa, formed hydroxyapatite after 72 h in SBF, and had no cytotoxicity and a considerable MG63 cells viability rate. These features make the scaffolds promising candidates for tissue engineering applications and worthy for further in vivo investigations.

Bioactive glass powders synthesized by solgel are usually porous and exhibit high specific surface areas, conferring them poor ability for scaffolds fabrication using colloidal processing approaches. The difficulties associated with colloidal processing of solgel glass have hindered so far the processing of 3‐D scaffolds by robocasting. This research paper investigates the importance of calcination temperature (CT) and balls to powder ratio (BPR) used upon wet milling on the maximum achievable solid loading in aqueous media. The effects of CT, BPR, and solid loading on the flow behavior and viscoelastic properties of the suspensions/pastes were evaluated in this preliminary work. The aim is to disclose the sets of experimental variables that are most promising for the formulation of printable inks, and open the way for the future fabrication of porous scaffolds by robocasting and other 3‐D additive manufacturing techniques.