Contact angle hysteresis on polymer substrates established with various experimental techniques, its interpretation,...

Area of Science:

• Materials Science
• Surface Science
• Polymer Science

Background:

• Contact angle hysteresis (CAH) influences surface wettability and is crucial for understanding liquid-solid interactions.
• Existing experimental techniques for CAH often involve volume changes, potentially introducing artifacts.
• Accurate measurement of CAH is essential for designing surfaces with controlled wetting properties.

Purpose of the Study:

• To investigate the effect of contact angle hysteresis (CAH) on various polymer substrates.
• To introduce and validate a new experimental technique for measuring CAH under constant droplet volume.
• To compare the results obtained from the new technique with traditional methods and analyze discrepancies.

Main Methods:

• Utilized traditional and a novel experimental technique to study CAH on polymer substrates.
• The new technique involves slow droplet deformation, maintaining a constant volume during measurement.
• Employed the improved Extrand approach to calculate the energy of hysteresis and the force pinning the triple line.

Main Results:

• The advancing contact angle measured with the new technique showed good agreement with the needle-syringe method.
• Significant discrepancies were observed in receding angles measured by three different experimental techniques.
• Calculated the force responsible for pinning the triple line, providing insight into the origins of hysteresis.

Conclusions:

• The new constant-volume droplet deformation technique offers a reliable method for measuring advancing contact angles.
• Discrepancies in receding angle measurements highlight the challenges and limitations of current experimental approaches.
• Understanding the pinning forces is key to controlling and predicting contact angle hysteresis in polymer systems.