PZT actuator applied to a femto-liter droplet ejector

Since the rapid advancement of the ink-jet printing technology, microdroplet ejectors have been developed into one of the essential fluid handling devices for delivering miniature liquid droplets in accurate dosage control. The applications of micro-droplet ejectors are increasingly prevalent in various emerging areas, for instance organic/polymer lighting emitting displays, liquid crystal display, optical communication, biochemical sample transport and screening and integrated circuit cooling devices. Among different inkjet printing technologies, piezoelectric driven droplet ejectors have shown their potential in dispensing diverse liquids. In this article, a novel femto-liter droplet ejector is proposed using a shear-type PZT actuator. To assure the workability of the ejector, the characteristics of the actuator were well investigated. Before integrating into the vibration plate of the ejector, the response of the rectangular plate-shaped actuator was evaluated by suspending the actuator on a fixture with both ends fixed. With a pre-specified driven waveform, the actuator vibrates to achieve satisfactory responses of displacement and velocity. Subsequently, the actuator was attached to the vibration plate as an actuating module for the ejector. The vibration plate has the design feature of a pillar on a diaphragm. The actuator pushed the pillar and thus deflected the diaphragm. The dimensions of the actuating module have been optimized by numerical simulations. The properties of diaphragm deformation and actuator transient response of the actuating module were simulated and measured for comparison purpose as well.