The droplet ejection of an inkjet mechanism controlled by electrorheological fluid

In a new design of printhead with ER fluid acting as a working medium, the actuating element and the ER fluid valve control the ink droplet ejection [Smart Mater. Struct. 9 (2000) 839–847]. In this paper, the transient behavior of the ER valve printhead incorporated with ink chamber is investigated. The pattern of ink droplet ejected from the printhead is examined by using the digital optical system for visualization. A quasi-static modeling of the system based on the bulk compressibility of the fluid and the stiffness of the elastic membrane is performed. The fluid pressure in the ink chamber is investigated, both theoretically and experimentally under the following controlled parameters: the actuating voltage and frequency of the piezoelectric transducer; and the controlled electric field strength of the ER value. It is found that the velocity of the ejected ink droplet increases with actuation voltage applied to the piezoelectric transducer. And a better ink droplet without satellite can be obtained with voltage impulse of magnitude 4 V, and pulse width of 6.5 ms. On the other hand, by applying 200 V/mm electric field on the ER valve, the ink ejection can be effectively stopped. Although the frequency of the ink ejection is limited to less than 10 Hz, due to the dynamic resonance of the system, it is believed that the operating bandwidth can be further raised by minimizing the dimensions of the system.