中国物理B ›› 2019, Vol. 28 ›› Issue (8): 84701-084701.doi: 10.1088/1674-1056/28/8/084701

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Non-Stokes drag coefficient in single-particle electrophoresis:New insights on a classical problem

Mai-Jia Liao(廖麦嘉), Ming-Tzo Wei(魏名佐), Shi-Xin Xu(徐士鑫), H Daniel Ou-Yang(歐陽新喬), Ping Sheng(沈平)   

  1. 1 Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China;
    2 Department of Physics, Lehigh University, Bethlehem, PA, USA;
    3 Department of Bioengineering, Lehigh University, Bethlehem, PA, USA;
    4 Centre for Quantitative Analysis and Modelling(CQAM), The Fields Institute, Toronto, Ontario M5T 3J1, Canada
  • 收稿日期:2019-07-19 出版日期:2019-08-05 发布日期:2019-08-05
  • 通讯作者: H Daniel Ou-Yang, Ping Sheng E-mail:hdo0@lehigh.edu;sheng@ust.hk

Non-Stokes drag coefficient in single-particle electrophoresis:New insights on a classical problem

Mai-Jia Liao(廖麦嘉)1,2, Ming-Tzo Wei(魏名佐)3, Shi-Xin Xu(徐士鑫)4, H Daniel Ou-Yang(歐陽新喬)2,3, Ping Sheng(沈平)1   

  1. 1 Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China;
    2 Department of Physics, Lehigh University, Bethlehem, PA, USA;
    3 Department of Bioengineering, Lehigh University, Bethlehem, PA, USA;
    4 Centre for Quantitative Analysis and Modelling(CQAM), The Fields Institute, Toronto, Ontario M5T 3J1, Canada
  • Received:2019-07-19 Online:2019-08-05 Published:2019-08-05
  • Contact: H Daniel Ou-Yang, Ping Sheng E-mail:hdo0@lehigh.edu;sheng@ust.hk

摘要:

We measured the intrinsic electrophoretic drag coefficient of a single charged particle by optically trapping the particle and applying an AC electric field, and found it to be markedly different from that of the Stokes drag. The drag coefficient, along with the measured electrical force, yield a mobility-zeta potential relation that agrees with the literature. By using the measured mobility as input, numerical calculations based on the Poisson-Nernst-Planck equations, coupled to the Navier-Stokes equation, reveal an intriguing microscopic electroosmotic flow near the particle surface, with a well-defined transition between an inner flow field and an outer flow field in the vicinity of electric double layer's outer boundary. This distinctive interface delineates the surface that gives the correct drag coefficient and the effective electric charge. The consistency between experiments and theoretical predictions provides new insights into the classic electrophoresis problem, and can shed light on new applications of electrophoresis to investigate biological nanoparticles.

关键词: electrophoresis, drag coefficient, vortices belt, charged colloidal particle

Abstract:

We measured the intrinsic electrophoretic drag coefficient of a single charged particle by optically trapping the particle and applying an AC electric field, and found it to be markedly different from that of the Stokes drag. The drag coefficient, along with the measured electrical force, yield a mobility-zeta potential relation that agrees with the literature. By using the measured mobility as input, numerical calculations based on the Poisson-Nernst-Planck equations, coupled to the Navier-Stokes equation, reveal an intriguing microscopic electroosmotic flow near the particle surface, with a well-defined transition between an inner flow field and an outer flow field in the vicinity of electric double layer's outer boundary. This distinctive interface delineates the surface that gives the correct drag coefficient and the effective electric charge. The consistency between experiments and theoretical predictions provides new insights into the classic electrophoresis problem, and can shed light on new applications of electrophoresis to investigate biological nanoparticles.

Key words: electrophoresis, drag coefficient, vortices belt, charged colloidal particle

中图分类号:  (Colloidal systems)

  • 47.57.J-
82.45.-h (Electrochemistry and electrophoresis) 47.61.-k (Micro- and nano- scale flow phenomena)