Bubble dynamics induced by pulsed-laser evaporation of ink as a method to develop novel print heads

The bubble dynamics induced by direct laser heating is experimentally analyzed as a first step to assess the technical feasibility of laser-based ink jet technology. To understand the interaction between laser light and ink, the absorption spectrum is measured for various ink colors and concentrations. The hydrodynamics of laser-generated bubbles is examined by laser flash photography. When an Ar ion laser pulse (wavelength 488 nm) with an output power up to 600 mW is incident on the ink solution through a transparent window, a hemispherical bubble with a diameter up to ∼100 μm can be formed with a lifetime in the range ∼O(10 μs) depending on the laser power and the focal-spot size. A parametric study has been performed to reveal the effect of laser pulse width, output power, ink concentration, and color on the bubble dynamics. The results show that the bubble generated by a laser pulse is largely similar to that produced by a thin film heater. Consequently, the present work demonstrates the feasibility of developing a laser-actuated droplet generation mechanism for applications in ink jet print heads. Furthermore, the results of this work indicate that the droplet generation frequency is likely to be further increased by optimizing the process parameters.