Interplay of electrokinetic effects in nonpolar solvents for electronic paper displays

Mohammad Khorsand Ahmadi; Wei Liu; Jan Groenewold; Jaap M J den Toonder; Alex Henzen; Hans M Wyss

doi:10.1016/j.jcis.2024.02.194

Interplay of electrokinetic effects in nonpolar solvents for electronic paper displays

J Colloid Interface Sci. 2024 Jul:665:263-273. doi: 10.1016/j.jcis.2024.02.194. Epub 2024 Mar 7.

Authors

Mohammad Khorsand Ahmadi¹, Wei Liu², Jan Groenewold³, Jaap M J den Toonder¹, Alex Henzen⁴, Hans M Wyss⁵

Affiliations

¹ Department of Mechanical Engineering, Microsystems, Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands; Institute for Complex Molecular Systems [ICMS], Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands.
² Department of Mechanical Engineering, Microsystems, Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands; Institute for Complex Molecular Systems [ICMS], Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands; South China Academy of Advanced Optoelectronics, Electronic Paper Display Institute, Guangzhou 510006, China.
³ South China Academy of Advanced Optoelectronics, Electronic Paper Display Institute, Guangzhou 510006, China; Department of Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, Utrecht, 3584 CH, Netherlands.
⁴ South China Academy of Advanced Optoelectronics, Electronic Paper Display Institute, Guangzhou 510006, China.
⁵ Department of Mechanical Engineering, Microsystems, Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands; Institute for Complex Molecular Systems [ICMS], Eindhoven University of Technology, Eindhoven, 5600 MB, Netherlands. Electronic address: H.M.Wyss@tue.nl.

PMID: 38485631
DOI: 10.1016/j.jcis.2024.02.194

Abstract

Hypothesis: Electronic paper displays rely on electrokinetic effects in nonpolar solvents to drive the displacement of colloidal particles within a fluidic cell. While Electrophoresis (EP) is a well-established and frequently employed phenomenon, electro-osmosis (EO), which drives fluid flow along charged solid surfaces, has not been studied as extensively. We hypothesize that by exploiting the interplay between these effects, an enhanced particle transport can be achieved.

Experiments: In this study, we experimentally investigate the combined effects of EP and EO for colloidal particles in non-polar solvents, driven by an electric field. We use astigmatism micro-particle tracking velocimetry (A-μPTV) to measure the motion of charged particles within model fluidic cells. Using a simple approach that relies on basic fluid flow properties we extract the contributions due to EP and EO, finding that EO contributes significantly to particle transport. The validity of our approach is confirmed by measurements on particles with different magnitudes of charge, and by comparison to numerical simulations.

Findings: We find that EO flows can play a dominant role in the transport of particles in electrokinetic display devices. This can be exploited to speed up particle transport, potentially yielding displays with significantly faster switching times.

Keywords: Astigmatism micro-particle tracking velocimetry; Colloids; Electro-osmosis; Electrokinetics; Electronic paper display; Electrophoresis; Nonpolar solvents; Surfactant.