Abstract
The stability of high-end piezoacoustic drop-on-demand (DOD) inkjet printing is sometimes compromised by the entrainment of an air bubble inside the ink channel. Here, bubble pinch-off from an oscillating meniscus is studied in an optically transparent DOD printhead as a function of the driving waveform. We show that bubble pinch-off follows from low-amplitude high-frequency meniscus oscillations on top of the global high-amplitude low-frequency meniscus motion that drives droplet formation. In a certain window of control parameters, phase inversion between the low- and high-frequency components leads to the enclosure of an air cavity and bubble pinch-off. Although phenomenologically similar, bubble pinch-off is not a result of capillary-wave interaction such as observed in drop impact on a liquid pool. Instead, we reveal geometrical-flow focusing as the mechanism through which, at first, an outward jet is formed on the retracted concave meniscus. The subsequent high-frequency velocity oscillation acts on the now toroidal-shaped meniscus and it accelerates the toroidal ring outward, resulting in the formation of an air cavity that can pinch off. Through incompressible boundary-integral simulations, we reveal that bubble pinch-off requires an unbalance between the capillary and inertial time scales and that it does not require acoustics. The critical control parameters for pinch-off are the pulse timing and amplitude. To cure the bubble entrainment problem, the threshold for bubble pinch-off can be increased by suppressing the high-frequency driving through appropriate waveform design. The present work therefore aids the improvement of the stability of inkjet printers through a physical understanding of meniscus instabilities.
| Original language | English |
|---|---|
| Article number | 044052 |
| Number of pages | 12 |
| Journal | Physical Review Applied |
| Volume | 16 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Oct 2021 |
Bibliographical note
Funding Information:Industrial Partnership Dutch Technology Foundation (STW) Foundation for Fundamental Research on Matter (FOM) Netherlands Organisation for Scientific Research (NWO) University of Twente Eindhoven University of Technology Canon Production Printing Netherlands B.V.
Funding Information:
This work is part of the research program “High Tech Systems and Materials” (HTSM), with project number 12802, and part of the Industrial Partnership Programme, number i43, of the Dutch Technology Foundation (STW) and the Foundation for Fundamental Research on Matter (FOM), which are part of the Netherlands Organisation for Scientific Research (NWO). The research was cofinanced by Canon Production Printing Netherlands B.V., the University of Twente, and Eindhoven University of Technology.
Funding
Industrial Partnership Dutch Technology Foundation (STW) Foundation for Fundamental Research on Matter (FOM) Netherlands Organisation for Scientific Research (NWO) University of Twente Eindhoven University of Technology Canon Production Printing Netherlands B.V. This work is part of the research program “High Tech Systems and Materials” (HTSM), with project number 12802, and part of the Industrial Partnership Programme, number i43, of the Dutch Technology Foundation (STW) and the Foundation for Fundamental Research on Matter (FOM), which are part of the Netherlands Organisation for Scientific Research (NWO). The research was cofinanced by Canon Production Printing Netherlands B.V., the University of Twente, and Eindhoven University of Technology.
