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Limits in measurements of contact lens surface profile using atomic force microscopy
Rafał Brygoła1, Sławomir Sęk2, Maciej Sokołowski1
1Faculty of Physics, University of Warsaw, Pasteura 7, 02-093 Warszawa, Poland.
Colloids and Surfaces. B, Biointerfaces
|February 28, 2018
Summary
Newer long-wear contact lenses (CL) show significantly lower surface roughness (RMS < 10 nm) compared to older models. Tip material choice in Atomic Force Microscopy (AFM) measurements also impacts roughness results.
Area of Science:
- Materials Science
- Ophthalmology
- Surface Metrology
Background:
- Surface topography of contact lenses (CL) is critical for comfort and wearability.
- Advancements in CL manufacturing aim to improve surface properties.
- Atomic Force Microscopy (AFM) is a key technique for nanoscale surface analysis.
Purpose of the Study:
- To present AFM surface profile measurements of seven new long-wear contact lenses (CL).
- To analyze and compare surface roughness parameters of modern CLs.
- To evaluate the influence of AFM tip material on measurement outcomes.
Main Methods:
- AFM surface profile measurements were performed on seven new long-wear CLs.
- Statistical roughness parameters including RMS, mean roughness, and kurtosis were calculated.
- Comparative measurements were conducted using a standard silicon tip and an alkylsilane-coated silicon tip.
Main Results:
- Newer CLs manufactured with advanced techniques (e.g., two-stage polymerization, extended silicon chains) exhibit low RMS values (< 10 nm).
- Older generation CLs showed significantly higher RMS values, in the tens of nanometers.
- Alkylsilane-coated tips resulted in higher RMS values (8.39 ± 0.16 nm) compared to standard silicon tips (6.22 ± 0.9 nm).
Conclusions:
- Modern manufacturing processes yield contact lenses with superior surface smoothness.
- The selection of AFM tip material is crucial and significantly affects surface roughness measurements.
- Understanding measurement limitations is essential for reliable surface characterization of CLs.
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