Abstract
This paper describes the fabrication, implementation and characterization of a thermal driven microinjector, featuring a bubble check valve and monolithic fabrication. Microfabrication of this microinjector is based on bulk/surface-combined micromachining of the silicon wafer, free of the bonding process that is commonly used in the fabrication of commercial printing head, so that even solvents and fuels can be ejected. Droplet ejection sequences of two microinjectors have been studied along with a commercial inkjet printhead for comparison. The droplet ejection of our microinjector with 10 μm diameter nozzle has been characterized at a frequency over 35 kHz, at least 3 times higher than those of commercial counterparts. The droplet volume from this device is smaller than 1 pl, 10 times smaller than those of commercial inkjets employed in the consumer market at the time of testing [1]. Visualization results have verified that our design, although far from being optimized, operates in the frequency several times higher than those of commercial products and reduces the cross talk among neighboring chambers. In addition, the reported device eliminates satellite droplets, one of the most trouble-some problems among top-shooting inkjets. The devices have been experimentally characterized and their key operation parameters are summarized.