Page 110 - IJB-9-6

International Journal of Bioprinting Affordable temperature-controlled bioprinter

Figure 2. Printing with GelMA at different temperatures, flow rates, and feed rates. (A) The rheology of GelMA-based hydrogels depends strongly on the
printing temperature: (i) Viscosity, and (ii) storage and loss moduli of 5% (w/v) GelMA and 3% GelMA+1% alginate at different temperatures. (B) A triad
of squares (programmed in G-code) was used to analyze the resolution of GelMA printings at different feed rates (linear printhead speeds) and flow rates.
(C) Printing of GelMA 5 × 5 mm at different feed rates and flow rates and temperatures: (i) water cooling set at 15°C and (ii) 25°C. (D) Side-by-side com-
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parison of a 5% GelMA ink extruded (i) without temperature control (i.e., ~25°C), and with temperature control at (ii) 15°C and 5°C.

holding the GelMA flow rate and water temperature ink improved remarkably when the temperature setting of
constant. In the design used here, the cylindrical ink/bioink the water cooler was further decreased to ~0°C. Figure 2D
chamber ended in a male Luer lock connector that accepts shows the comparison between three letters printed
standard needles as extruder tips. Figure 2C shows the sets without any temperature control (i.e., ~25°C; Figure 2Di)
of squares printed through a 21G needle at the temperature and with temperature control (i.e., water circulator set at
settings of 15°C and 20°C for the water circulator at 0°C; Figure 2Dii). The definition of each letter improves
three different GelMA feed rates. These settings induce dramatically and their shape is retained through UV
temperatures of ~20°C and 25°C at the tip of the printing crosslinking (i.e., ~60 s).
nozzle, respectively; temperature values that are in the
neighborhood of the gel–liquid transition. The resolution Next, we further assessed the printability of series of
and fidelity of the printed squares improves qualitatively as squares printed at low-temperature settings. Figure 3A
the temperature setting decreases, and completely closed shows the sets of squares printed through a 21G needle
squares can be obtained in most of the feed and flow rate at the low temperature setting of 0°C for the water
combinations tested. The printability of the 5% GelMA circulator at three different GelMA feed rates. Note that

Volume 9 Issue 6 (2023) 102 https://doi.org/10.36922/ijb.0244