一种用于水下精确测量动态接触角的推动-拉拽封闭气泡方法
A pushing-pulling captive bubble method for repeatable measurement of dynamic contact angles underwater
AI总结：
本文提出一种推动-拉拽封闭气泡方法，用于水下稳定测量动态接触角，通过控制垂直运动实现气泡与表面的稳定接触，提高了测量精度和可重复性，尤其适用于微结构表面的测量。
摘要：
准确测量水环境中动态接触角对于评估表面润湿性至关重要。然而，传统封闭气泡方法常面临气泡不稳定和针湿干扰等问题。本文开发了一种推动-拉拽封闭气泡方法，可在不直接改变气泡体积的情况下实现水下稳定和精确测量动态接触角。该方法通过受控的垂直运动将气泡推至并脱离表面，从而在抑制气泡变形和横向运动的同时实现稳定的接触线观察。动态接触角在空气和水中的测量结果表明，对于光滑和Wenzel表面，空气和水中的动态接触角值相似。此外，改进的封闭气泡方法的可重复性与传统方法相当或更高。对于微结构表面，动态接触角测量在水中的困难在于表面会残留空气层。本文通过超声波脱气实现了完全润湿条件下的动态接触角测量，揭示了与空气中观察到的行为显著不同的现象。
英文摘要：
Accurate measurement of dynamic contact angles in aqueous environments is essential for evaluating surface wettability. However, conventional captive bubble methods often suffer from limitations such as bubble instability and interference from needle wetting. In this study, we develop a pushing-pulling captive bubble method that enables stable and repeatable measurement of dynamic contact angles underwater without directly changing the bubble volume. In this method, a bubble is pushed against and detached from a surface by controlled vertical motion. This procedure allows stable observation of the contact line while suppressing bubble deformation and lateral movement. Dynamic contact angles were measured in both air and water using three types of surfaces: smooth surfaces, sandpaper-polished surfaces prepared to exhibit the Wenzel state in air and the reversed gas-liquid Wenzel state in water, and microstructured surfaces exhibiting hydrophobicity in air. For smooth and Wenzel surfaces, the dynamic contact angles measured in air and water showed similar values. Moreover, the modified captive bubble method exhibited reproducibility comparable to that observed in conventional captive bubble methods under the present experimental conditions. For microstructured surfaces, dynamic contact angle measurements in water had previously been difficult because an air layer remained trapped on the surface. In this study, ultrasonic degassing enabled dynamic contact angle measurements under fully wetted conditions, revealing behavior that differed significantly from that observed in air.
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