An ink-jet head using diaphragm microactuator

An ink-jet head using a buckling diaphragm microactuator is described. The microactuator is composed of a silicon substrate, silicon dioxide insulator, nickel heater and electro-plated nickel diaphragm. All the edges of the diaphragm are fixed on the substrate and a narrow gap is formed between the diaphragm and the substrate. A nozzle plate is connected to the actuator by an adhesive spacer to get the ink-jet head. An ink chamber is formed by the surfaces of the diaphragm, the nozzle plate, and the side wall of the spacer. When the diaphragm is heated, thermally induced compressive stress causes the diaphragm to buckle rapidly and the diaphragm simultaneously deflects toward the nozzle plate. The deflection raises the pressure in the ink chamber and an ink droplet is then ejected through the nozzle. The ink-jet head has been designed to maximize the droplet velocity, minimize the thermal response of the actuator and optimize the energy consumption needed to eject an ink droplet. The head design was carried out by using mechanical analysis of a buckling model, and heat transfer simulation. The diaphragm made from nickel is 300 μm diameter and 2 μm-thick. The microactuator has been built using a combination of surface- and bulk-micromachining. An ink droplet has been ejected with a velocity of 8 m/s while the ink-jet head is operated by heating the diaphragm with a current of 510 mA at 16.6 V for 10 μs at 1.8 kHz. We assured that no bubble was generated at less than 1.8 kHz. The fabrication process used to make the microactuator is briefly reported