Figure 2
From: Handheld Co-Axial Bioprinting: Application to in situ surgical cartilage repair
Higher concentration of LAP photoinitiator favour higher storage modulus. In situ photo-rheometry of GelMa/HAMa hydrogels incorporating LAP during the crosslinking reaction. Each plot shows storage modulus as a function of time with the UV light (365 nm, 100 mW/cm2) switched on at 100 s. (A) Storage modulus as a function of continuous UV exposure time for four concentrations of LAP (0.005% = open squares, 0.01% = light grey squares, 0.05% = grey squares and 0.1% = black squares). Both the reaction rate and the final storage modulus are impacted by LAP concentration. Low concentrations produce slow reactions resulting in low modulus hydrogels. The two highest LAP concentrations (0.05% and 0.1%) achieve comparable final modulus (~70 kPa), although the 0.05% concentration requires much longer exposure time to achieve this. (B) Effect of dark polymerization. GelMa/HAMa hydrogels incorporating 0.1% LAP were exposed to continuous UV exposure (thick black line) or single bursts of short times (10 s, 2 s and 1 s). The arrows indicate the point at which the UV light was switched off for the continuous exposure (100 s). During light exposure, all hydrogels follow similar crosslinking kinetics, however after the light turns off dark polymerization can continue for many minutes. In the case of the 10 s exposed hydrogel, the dark polymerization is sufficient to match the material crosslinked with a (much longer) continuous exposure.
