Noncontact axial-vibration drop-on-demand jetting enabled by sub-pulse compensation and resonant amplification

Noncontact-actuated drop-on-demand (DOD) jetting isolates the actuator from harsh liquid environments, improving reliability and material compatibility. Here, we develop a lead zirconate titanate (PZT)–connector–tube–nozzle indirect axial-vibration architecture and clarify how the architecture transmits and reshapes PZT-side vibration into nozzle motion from low-frequency pulsed actuation to high-frequency periodic excitation. Under low-frequency single-pulse drive, experiments and simulations show that coupled residual nozzle vibration and meniscus oscillation can trigger multiple ejection events; introducing a precisely delayed sub-pulse suppresses the residual nozzle motion and enables single-ejection operation under a single-pulse command. Under high-frequency periodic excitation, the system approaches a steady-state forced-vibration regime. Time- and frequency-domain analyses reveal that, in the PZT–connector–tube–nozzle architecture, the nozzle response differs from the PZT-side vibration because of connector-assisted dynamic transmission. The assembled architecture exhibits a dominant response near 14 kHz, where the nozzle displacement is ∼2.8 times that of the PZT, accompanied by attenuation of non-dominant harmonic components. This resonant amplification reduces the required drive to reach the jetting threshold and improves droplet generation for challenging fluids with high surface tension and/or high viscosity. With coordinated control of voltage, frequency, and liquid supply pressure, the device achieves reproducible droplet generation for a glycerol/ethanol (1:2, v/v) mixture and enables Galinstan droplet formation under a nitrogen atmosphere. These results provide transferable design and waveform-guidance for noncontact DOD jetting in functional material printing and extreme-environment droplet generation.