Tilting of adjacent laser-induced liquid jets

The effects of time delay and spatial separation between two adjacent laser pulses in blister-actuated laser-induced forward transfer are studied experimentally and computationally. Each laser pulse creates a blister that expands into a liquid film, forming liquid jets to transfer material from a donor substrate to an acceptor substrate. For a fixed separation between the two laser pulses, time-resolved imaging reveals a tilting of the second liquid jet toward or away from the first jet, depending on the time delay between pulses. Simulations of the same process reveal that the first jet perturbs the ink-air interface around it, and the initial angle of the liquid-air interface below the second laser pulse is shown to be a good predictor of the angle of the second jet. The time evolution of the initial interface angle at a fixed separation is then investigated analytically in terms of a viscously damped cylindrical capillary wave, initiating once the jet retracts or pinches off. This two-jet setup can be considered as a model system for high repetition rate printing, so these results reveal limits on the repetition rate and separation between pulses for LIFT such that materials are printed in desired patterns.