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Volume 16, No. 12, December 2016, Pages 3055-3062 PDF(1.33 MB)  
doi: 10.4209/aaqr.2016.04.0147   

Experimental Evidence of a Strong Image Force between Highly Charged Electrosprayed Molecular Ions and a Metal Screen

Youichi Omori1, Hyun-Jin Choi2, Yasuaki Mukai2, Toshiyuki Fujimoto3, Tomoya Tamadate2, Takafumi Seto2, Yoshio Otani2, Mikio Kumita2

1 Sanzen Seishi Co. Ltd., Kanazawa, Ishikawa 920-0338, Japan
2 School of Natural System, College of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
3 Department of Applied Sciences, Muroran Institute of Technology, Muroran, Hokkaido 050-8585, Japan


  • Investigation of capturing mechanisms of highly charged ions onto metal screen.
  • Experimental and theoretical examinations of the collection efficiencies.
  • Strong contribution of image force to multicharged ion capturing onto metal screen.



We investigated the capturing mechanisms of highly charged macromolecular ions of polyethylene glycol electrosprayed onto a metal screen. Our experiments assessed how the charge state, size of the macromolecular ions, and filtration velocity affected the penetration of the ions through the metal screen. The single fiber efficiencies were plotted as functions of the Peclet number and image force parameter. Highly charged molecular ions had much higher collection efficiencies than neutralized macromolecules, suggesting the presence of a strong image force between the ions and metal surface. The single fiber efficiency by image force was proportional to the square root of an image force parameter predicted by theory. When using the prefactor of 9.7 proposed by Alonso et al. (2007), we found fair agreement between the experimental data and theoretical predictions on the collection efficiency of highly charged molecular ions with mobility diameters from 2.6 to 4.8 nm and numbers of electrical charges from 2 to 7. The experimental evidence from our study reveals that image force contributes strongly to the collection of multicharged macromolecular ions by a metal wire screen.



Keywords: Image force; Metal screen; Electrospray; Molecular ion.



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