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Conversion of Polymer Surfaces into Nonwetting Substrates for Liquid Metal Applications
Sachin Babu1, Behnoush Dousti1, Gil Sik Lee1
1Department of Electrical and Computer Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 28, 2021
Summary
A novel plasma treatment makes common polymers non-wetting for liquid metals. This process enhances surface roughness and fluorination, crucial for advanced liquid metal applications.
Area of Science:
- Materials Science
- Surface Science
- Polymer Science
Background:
- Liquid metal applications are hindered by polymer wetting on oxidized gallium-based liquid metals.
- Developing non-wetting polymer surfaces is critical for advancing liquid metal technologies.
Purpose of the Study:
- To investigate the effect of CF4/O2 plasma treatment on polymer surfaces for liquid metal applications.
- To convert wetting polymer surfaces into non-wetting (lyophobic) surfaces for gallium-based liquid metals.
Main Methods:
- Polymer surfaces (PDMS, SU8, S1813, polyimide) were treated with CF4/O2 plasma for 120 seconds.
- Contact angle measurements (static, advancing, receding) were used to quantify wetting behavior.
- X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyzed surface chemistry and topography.
Main Results:
- Plasma treatment resulted in contact angles >150° (static/advancing) and >140° (receding), indicating significant lyophobic behavior.
- Surface analysis revealed simultaneous fluorination and a substantial increase in surface roughness (sub-micron scale).
- The Cassie-Baxter state, driven primarily by roughness, was suggested as the mechanism for non-wetting properties.
Conclusions:
- CF4/O2 plasma treatment effectively transforms wetting polymer surfaces into non-wetting ones for gallium-based liquid metals.
- Surface roughness, augmented by plasma treatment, is the dominant factor in achieving lyophobic behavior.
- This method offers a versatile approach to reduce surface free energy and enhance compatibility in liquid metal-polymer systems.
