Investigating the Response of a Piezoelectric Actuator to Different Waveforms and its Effects on Capillary Jet Breakup

In this paper, we study the response of a practical piezoelectric transducer, used to initiate droplet pinch-off in a capillary jet, to different driving waveforms at different frequencies. The study also examines how the piezoelectric’s response affects the jet breakup into droplets. Here we study sine wave and square wave periodic signals. The piezoelectric vibrates when a periodic voltage with one of these types of waveforms is applied to its terminals. At some frequencies, the output motion of the actuator driven with square wave includes several harmonics. The output of the piezoelectric is then applied as the input disturbance to a jet of liquid in the form of a velocity perturbation. In this way, the piezoelectric displacement initiates the liquid jet breakup. We determine experimentally the actuator frequency response by measuring the output displacement of the piezoelectric vibration with a laser Doppler vibrometer. In particular, to study the response of the device, we sweep the driving frequency of the input signal at constant voltage amplitude and measure the output displacement of the piezoelectric. Then, we compare the output signals generated from the sine wave input with the ones generated from square wave input signals. Studying the effects of the output signal of the piezoelectric driven with different waveforms on droplet breakup helps determine the conditions most favorable to the production of droplets.