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Surfactant control of coffee ring formation in carbon nanotube suspensions

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journal contribution
posted on 2023-01-24, 15:01 authored by Naomi HowardNaomi Howard, Andrew ArcherAndrew Archer, David SibleyDavid Sibley, Darren SoutheeDarren Southee, Upul Wijayantha-Kahagala-Gamage

The coffee ring effect regularly occurs during the evaporation of colloidal droplets and is often undesirable. Here we show that adding a specific concentration of a surfactant can mitigate this effect. We have conducted experiments on aqueous suspensions of carbon nanotubes that were prepared with cationic surfactant dodecyltrimethylammonium bromide added at 0.2, 0.5, 1, 2, 5, and 10 times the critical micelle concentration. Colloidal droplets were deposited on candidate substrates for printed electronics with varying wetting characteristics: glass, polyethylene terephthalate, fluoroethylene propylene copolymer, and polydimethylsiloxane. Following drying, four pattern types were observed in the final deposits: dot-like, uniform, coffee ring deposits, and combined patterns (coffee ring with a dot-like central deposit). Evaporation occurred predominantly in constant contact radius mode for most pattern types, except for some cases that led to uniform deposits in which early stage receding of the contact line occurred. Image analysis and profilometry yielded deposit thicknesses, allowing us to identify a coffee ring subfeature in all uniform deposits and to infer the percentage coverage in all cases. Importantly, a critical surfactant concentration was identified for the generation of highly uniform deposits across all substrates. This concentration resulted in visually uniform deposits consisting of a coffee ring subfeature with a densely packed center, generated from two distinct evaporative phases.

Funding

Engineering and Physical Sciences Research Council (EPSRC)

History

School

  • Design and Creative Arts
  • Mechanical, Electrical and Manufacturing Engineering
  • Science

Department

  • Chemistry
  • Design
  • Mathematical Sciences

Published in

Langmuir

Volume

39

Issue

3

Pages

929-941

Publisher

American Chemical Society

Version

VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by American Chemical Society under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/

Acceptance date

2022-12-07

Publication date

2023-01-06

Copyright date

2023

ISSN

0743-7463

eISSN

1520-5827

Language

en

Depositor

Prof Andrew Archer. Deposit date: 14 January 2023