Active droplet oscillation excited by optimized waveform: Experiments reveal the effects of waveform parameters on the excited droplet oscillation, plus the optimal range of current waveform parameters is determined

The active droplet oscillation method is an approach previously proposed to detach the droplet at currents below the transition current. In this method, a droplet oscillation is first excited by intentionally switching the current from the peak to base level; the downward momentum of the oscillating droplet is then utilized to enhance the droplet detachment such that the droplet can be detached at reduced peak currents lower than the transition current. In the present work, this method is systematically studied to initiate stronger oscillations with lower average currents. To this end, the current waveform is modified by differentiating the exciting current from the growing current. This differentiation enables the growing current (heat input) be reduced without affecting the oscillation excitation. The current waveform is then further modified by adding a base period before the exciting pulse to maximize the oscillation, resulting in an optimized waveform. A series of experiments has been conducted to correlate the droplet oscillation to the parameters in the optimized waveform. The optimal ranges for the waveform parameters are experimentally determined. The active droplet oscillation method is improved at a fundamental level, and its mechanism is also better understood.