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Long-term reduction in poly(dimethylsiloxane) surface hydrophobicity via cold-plasma treatments
B J Larson1, S D Gillmor, J M Braun
1Department of Materials Science and Engineering, University of Wisconsin-Madison , 1509 University Avenue, Madison, Wisconsin 53706, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|September 26, 2013
Summary
New plasma treatments permanently reduce hydrophobicity in poly(dimethylsiloxane) (PDMS) surfaces, crucial for microfluidic devices. These methods enable stable surface properties for applications like DNA array formation.
Area of Science:
- Materials Science
- Surface Chemistry
- Microfluidics
Background:
- Poly(dimethylsiloxane) (PDMS) is a widely used elastomer in microfluidics due to its favorable properties.
- Unmodified PDMS surfaces are inherently hydrophobic, limiting their application in certain microfluidic systems.
- Standard oxygen plasma treatments for PDMS hydrophobicity reduction are temporary, with surfaces reverting to their hydrophobic state.
Purpose of the Study:
- To develop long-term hydrophobic modification methods for PDMS surfaces.
- To investigate alternative plasma treatments beyond standard oxygen plasma.
- To explore applications benefiting from stable PDMS surface wettability.
Main Methods:
- Investigated two novel plasma treatment protocols: oxygen plasma followed by SiCl4 plasma, and oxygen-CCl4 mixture plasma.
- Utilized X-ray photoelectron spectroscopy (XPS) to analyze surface elemental composition and chemical states.
- Employed contact angle measurements to quantify surface wettability and hydrophobicity.
Main Results:
- Both SiCl4 and oxygen-CCl4 plasma treatments resulted in a permanent reduction in PDMS surface hydrophobicity.
- XPS analysis indicated the incorporation of polar groups onto the PDMS surface.
- Contact angle measurements confirmed sustained changes in surface wetting properties over time.
Conclusions:
- The developed plasma treatments offer a durable solution for modifying PDMS surface wettability.
- The modified surfaces are proposed to be a dynamic mosaic, preventing re-coverage by low-molecular-weight PDMS groups.
- These stable PDMS surfaces have potential applications, such as forming dense DNA arrays on surfaces.
