Control of viscosity of gelatin methacryloyl bioink by ultrasound sonication for inkjet bioprinting

Abstract

Drop-on-demand inkjet printing, one of the most effective tools for tissue fabrication, allows high resolution printing by positioning very small droplets of liquid in a picolitre (10-12 L) level. However, a limited range of polymer concentration is printable as this technique cannot print an ink with viscosity of above 20 mPa·s. Here, we report a simple method to control the viscosity of high-concentration gelatin mathacryloyl(GelMA) bioinks by exposing ultrasound sonication to print with an inkjet-print nozzle. We prepared GelMA inks with varying concentration from 5 to 10 and 15 % (w/v). Those inks were exposed to ultrasound sonication with different duration from 0 to 48 min to lower their viscosity which were measured with a rotational rheometer. By increasing the sonication time, the viscosity of GelMA inks decreased with the shortened chain length of peptide polymer. The 10% GelMA which was initially unjettable with an 80 μm-sized inkjet nozzle turns out to be jettable owing to the reduction of viscosity by ultrasound sonication. The 5% GelMA inks were jettable and 15% GelMA inks were not jettable regardless ultrasound exposure. We believe that this method enables us to expand inkjet-ink range and control ink physical properties easily.