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Reverse movement and coalescence of water microdroplets in electrohydrodynamic atomization
L L F Agostinho1, E C Fuchs, S J Metz
1Wetsus Centre of Excellence for Sustainable Water Technology, Agora 1, NL-8900 CC Leeuwarden, The Netherlands.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 21, 2011
Summary
Charged water droplets formed via electrohydrodynamic atomization (EHDA) can reverse direction due to electric field polarization. Their charge was calculated to be between 2.5% and 19% of the Rayleigh limit.
Area of Science:
- Physics
- Chemistry
- Materials Science
Background:
- Electrohydrodynamic atomization (EHDA), or electrospray, generates charged microdroplets.
- These droplets typically follow electric field lines away from the source.
- Understanding droplet behavior is crucial for applications like mass spectrometry and materials deposition.
Purpose of the Study:
- To investigate the phenomenon of charged water droplet path reversal during EHDA.
- To quantify the charge of these droplets and compare it to theoretical limits.
- To elucidate the underlying physical mechanism driving the reverse movement.
Main Methods:
- Utilizing high-speed imaging to capture droplet trajectories.
- Developing a method to calculate droplet charge from observed paths.
- Analyzing droplet behavior under strong electric fields.
Main Results:
- Observed water droplets reversing direction and moving back towards the liquid meniscus.
- Calculated droplet charges ranging from 2.5% to 19% of their Rayleigh limit.
- Attributed the reverse motion to polarization of water molecules within the electric field.
Conclusions:
- The polarization of water in strong electric fields can induce reverse motion in electrosprayed droplets.
- The calculated charge values provide insight into the droplet dynamics and stability.
- This finding enhances the understanding of electrospray physics and its controlling parameters.
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