Abstract: To print cells and maintain high cell viability, a pneumatic droplet-on-demand (DOD) system was designed. The key components of the system included a chamber for liquid sample, a tiny orifice of 100μm. The chamber was connected to a Nitrogen gas tank with a high speed solenoid valve, and to the ambiance with a venting tube. A photographic system was used to evaluate the uniformity and consistency of the DOD system. A pressure pulse was created within the chamber via controlling the solenoid valve. The liquid was pushed out through the nozzle, generating a droplet. The gas was then released through the venting tube, recovering the system back to equilibrium. As confirmed by the photographic system, stable generation of single droplet was realized, with a generation frequency of 20Hz, and with droplet diameter around 200μm. Finally, jetting of human peripheral blood lymphocytes (PBL) and buffer was tested. Based on flow cytometry studies, the impacts of the micro-drop generation process on viability of the human PBLs were found to be negligible.