Physics and Astronomy Publications
Document Type
Article
Publication Date
2013
Journal
Langmuir
Volume
29
First Page
2615
Last Page
2622
URL with Digital Object Identifier
https://doi.org/10.1021/la303940a%40proofing
Abstract
The effect of electrostatic interaction between carboxylate- and amino-functionalized polystyrene particles and a charged waveguide surface on the propulsion speed in an optical tweezers is considered as a function of pH and ionic strength. It was shown that with the variation of the pH of the aqueous solution, the particles were immersed in, a systematic change of propulsion speed with a maximum speed could be achieved. The appearance of a maximum speed was ascribed to changes in the particle-waveguide separation as a result of the combination of two forces: Coulomb repulsion/attraction and induced dipole forces. The highest maximum speed at low ionic strength was around 12 µm/sec. Changes in the ionic strength of the solution influenced the gradient of the dielectric constant near the involved surfaces and also lead to a slightly reduced hydrodynamic radius of the particles. The combination of these effects subsequently increased the maximum speed to about 23 µm/sec.
