Todd Brian A, Cohen Joel A
Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Sep;84(3 Pt 1):032401. doi: 10.1103/PhysRevE.84.032401. Epub 2011 Sep 26.
By use of optical tweezers we explicitly measure the electrostatic and hydrodynamic forces that determine the electrophoretic mobility of a charged colloidal particle. We test the ansatz of O'Brien and White [J. Chem. Soc. Faraday II 74, 1607 (1978)] that the electrostatically and hydrodynamically coupled electrophoresis problem is separable into two simpler problems: (1) a particle held fixed in an applied electric field with no flow field and (2) a particle held fixed in a flow field with no applied electric field. For a system in the Helmholtz-Smoluchowski and Debye-Hückel regimes, we find that the electrostatic and hydrodynamic forces measured independently accurately predict the electrophoretic mobility within our measurement precision of 7%; the O'Brien and White ansatz holds under the conditions of our experiment.
通过使用光镊，我们明确测量了决定带电胶体颗粒电泳迁移率的静电力和流体动力。我们检验了奥布赖恩和怀特[《化学学会会刊·法拉第学报II》74, 1607 (1978)]的假设，即静电和流体动力耦合的电泳问题可分为两个更简单的问题：(1) 一个颗粒在施加的电场中固定不动且无流场；(2) 一个颗粒在无施加电场的流场中固定不动。对于处于亥姆霍兹 - 斯莫卢霍夫斯基和德拜 - 休克尔区域的系统，我们发现在7%的测量精度范围内，独立测量的静电力和流体动力能准确预测电泳迁移率；奥布赖恩和怀特的假设在我们的实验条件下成立。
