High Repetition Rate Laser‐Induced Printing of Bioink with Picosecond Pulse Durations: Optimization of the Printing Process

It has been more than two decades since laser‐induced forward transfer (LIFT) was studied on a laboratory scale for its ability to print biomaterials. Most of the published works in this field are focused on the use of nanosecond lasers. Our final objective is to use the LIFT technique in a picosecond regime to create in vitro biomodels for tissue engineering and regenerative medicine applications. But in a first approach, the work presented here focuses on hydrodynamics and rheological studies for the optimization of the process for bioapplications. In order to precisely control the amount and position of the deposited material, it is necessary to carefully investigate the jetting dynamics as a function of various parameters, including the laser fluence and the rheological properties of the bioink. In this study, time‐resolved fast imaging is used to investigate the hydrodynamics of the transfer of successive jets at a high pulse repetition rate. Different conditions have been determined (bioink viscosity, specific jetting dynamic associated with a precise distance for printing, and laser parameters) for precise control of the quantity of ink and number of cells deposited per droplet associated with high accuracy on their location and good reproducibility of the printing process.