A novel microinjector with virtual chamber neck

This paper describes a thermally driven droplet-injector which employs a novel concept of "virtual chamber neck". The idea is to either isolate the microchamber from the liquid supply or connect to it by forming or collapsing a bubble at the chamber entrance. The use of bubble valves instead of actual valves enables fast and reliable device operation yet makes the fabrication simple. Microfabrication of this microinjector is based on monolithic bulk/surface-combine micromachining of silicon, free of the wafer bonding commonly used in printing industry. The droplet ejection is characterized at frequencies over 2 kHz by using a visualization method. Testing results show that our design reduces the cross talk among neighboring chambers and eliminates the satellite droplet, one of the most troublesome problems in inkjet.