Effects on wettability by surfactant accumulation/depletion in bulk polydimethylsiloxane (PDMS)

Jeonggi Seo, Luke P. Lee

Research output: Contribution to journalArticlepeer-review

98 Scopus citations

Abstract

Polydimethylsiloxane (PDMS) is an appealing silicone elastomer as a base material for microfluidic biomedical applications. Its ability to easily cross-link as well as its favorable physical and chemical properties has enabled a large number of micro- and nano-cast applications. However, PDMS' hydrophobic surface can be problematic. Two methods presented here address the wettability of PDMS by accumulating or depleting surfactant in PDMS. The surfactant in the cross-linked PDMS matrix is released and activated upon contacting with an aqueous solution and assists the solution wetting of PDMS. Wettability was enhanced as a function of surfactant concentration. With the addition of 3% Triton TX-100 (a nonionic surfactant), the contact angle of deionized water on PDMS decreased up to 40° in 90 s, compared with a decrease of only 3° on unmodified PDMS. Dynamic measurements of contact angle and contact line radii showed wettability change due to the transfer of surfactant to the interface of the aqueous solution/PDMS. The stability of the modified PDMS was quantified by contact angle measurements over a 30-day duration. Immersing the modified PDMS in water for long time periods before the measurement depletes the surfactant; the resulting wettability becomes a function of immersion duration. The surface wettability can also be controlled with a function of immersion duration even after the PDMS is cured.

Original languageEnglish
Pages (from-to)192-198
Number of pages7
JournalSensors and Actuators, B: Chemical
Volume119
Issue number1
DOIs
StatePublished - 24 Nov 2006

Keywords

  • Contact angle measurement
  • Microfluidics
  • Polydimethylsiloxane (PDMS)
  • Surface modification
  • Triton X-100

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