Robocasting: Prediction of ink printability in solgel bioactive glass

Abstract

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.

Robocasting of ceramic glass scaffolds: Sol–gel glass, new horizons

“…This task has been accomplished by using sophisticated equipment such as attrition mill [25] and planetary milling [21] for different time periods up to 4 h. The milling efficiency strongly depends on the milling conditions, namely on the rotation speed and the balls to powder ratio (BPR). A suitable control of these variables was shown to enable shortening the milling time of our sol-gel bioactive glasses to 1 h using a simple equipment [27]. Following the same strategy used here is likely to open new research avenues for the fabrication of sol-gel derived bioactive glass scaffolds by robocasting.…”

“…The as-dried gel was heat treated in air according to the following three-stage heat treatment schedule: 1 st stage, from RT to 200°C at the heating rate of 1°C min -1 ; 2 nd stage, from 200°C to 400°C, at the heating rate of 2°C min −1 ; and the 3 rd stage, from 400°C to 800°C, at the heating rate of 5°C min −1 , then 2 h dwell time at 800°C, followed by natural cooling. The heat treatment to 800°C was selected based on the findings of a previous work [27], showing that the elimination of…”

“…For instance, a powder volume of 0.8 cm 3 (1.7984 g) will be required to prepare 2 ml of a paste containing 40 vol.%. The preparation of the inks and optimisation procedures were performed according to the outputs of our systematic previous study [27].…”

“…(5 -2), reveal that within the pore size range tested, pore size does not exert any significant influence on cell viability. The dashed line represents the cut-off of 30% of reduction of cell viability -according to ISO 10,993-5, the test item is considered non-cytotoxic if the percentage of viable cells is equal to or greater than 70% of the untreated control [27]. Therefore, all of these scaffolds can be considered to be fully biocompatible with osteoblasts.…”

“…Although these features of sol-gel derived glasses are advantageous in terms of bioactivity, such features supposedly constitute the main barriers towards using these powders in robocasting. This issue was recently tackled by the authors in an attempt to overcome these constrains in the formulation of ink and predicting ink printability [27]. It was shown that significant progresses could be made by playing with the heat treatment temperature (HTT) and with the milling conditions, which determine the particle size (PS), particle size distribution (PSD) and porous fraction of the synthesised powder.…”