Droplets generator: Formation and control of main and satellite droplets


Procedures such as printing of electronics, DNA arranging, formation of three-dimensional objects by the deposition of molten metal droplets, drug and food manufacture- among others, apply uniform droplets production technology. Continuous ink jet (CIJ) and drop-on-demand (DOD) printing techniques have been applied widely for producing uniform droplets. A comparison of the two has shown that the latter has a higher droplets formation frequency. As for the CIJ technique, during droplet formation, the breakup process of jet-flow is normally affected by some factors, namely; gas pressure, perturbation frequency and nozzle diameter. CIJ technology is an effective and important method for formation of uniform droplets by optimizing experiment parameters.

Previous studies have shown that perturbation imposed on the surface of the jet-flow is one of the primary parameters to control droplets formation. Presently, the desired perturbation is normally produced by a piezoelectric transducer. Unfortunately, it typically uses a medium, such as vibrational rod, to amplify the perturbation amplitude, and the structure of the whole system is complicated. Therefore, a facile stable means of generating stable disturbance is necessitated.

Recently, researchers led by Dr. Tongju Wang and colleagues from the School of Materials Science and Engineering at Beijing University of Technology presented a novel technique of producing stable disturbance wave. Their main objective was to study the droplets breakup modes at different nozzle diameters. As such, the main feature of their new method was that the pulse electromagnetic force was produced and imposed on an elastic diaphragm when an external constant electromagnetic field and an internal pulsed current passed through gallium-based liquid metal. Their work is currently published in the research journal, Colloids and Surfaces A.

The researchers assessed the effects of disturbance frequency on the length of surface wave and diameter of droplets. Additionally, the relationship between the gas pressure and the region of uniform droplets formation was studied, where the effects of; gas pressure on the formation of uniform droplets, disturbance frequency on the wavelength of surface wave and disturbance frequency on the droplet’s diameter were all assessed. All in all, the application of high-speed photography technology along with image processing, enabled the researchers to investigate droplet formation at different nozzle diameter and disturbance frequency.

The authors observed that the droplets formation experienced different breakup modes at different nozzle diameters. Moreover, the experimental results indicated that the jet had different breakup modes at different nozzle diameters. They also established that the gas pressure and the disturbance frequency had a significant effect on droplets formation.

In summary, the study by Beijing University of Technology researchers presented a simple method for producing steady disturbance. Generally, the scholars were able to establish that the wavelength of surface wave decreased with the rise of the disturbance frequency. More so, they realized that the model was able to illuminate the relationship between the disturbance frequency and the wavelength of surface wave. The diameter of droplets decreased with the rise of the disturbance frequency. Altogether, a facile technique that would enable seamless production of droplets using CIJ was established.

About the author

Dr. Tongju Wang is an researcher in droplets formation and the production of solder ball. He received his master of material processing engineering from Southwest Petroleum University, China. He then enrolled in the doctoral programs of material processing engineering under the supervision of professor Yongping Lei at Beijing University of Technology (BJUT), China.

Dr. Tongju Wang has published a series of research papers on some scientific journals, such as: Vacuum, Review of Scientific Instruments and Colloids and Surfaces A. Moreover, he has applied 4 invention patents of China.

Email address: [email protected] (Tongju Wang).

About the author

Yongping Lei is a professor of material processing engineering at Beijing University of Technology (BJUT). He received his B.S. degree and M.S. degree in materials science and engineering from Northwestern Polytechnical University, and Ph.D. degree from Xi ‘an Jiaotong University.

Prof. Yongping Lei is known internationally for his research on materials of microelectronic assembly, wire-arc additive manufacturing, numerical simulation of material processing, the uniform droplets formation and the production of solder ball.

Email address: [email protected] (Yongping Lei).


Tongju Wang, Jian Lin, Yongping Lei, Xingye Guo, Hanguang Fu. Droplets generator: Formation and control of main and satellite droplets. Colloids and Surfaces A, volume 558 (2018) page 303–312.

Go To Colloids and Surfaces A

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