二元液体混合物滴状受限干燥：在湿度控制下的定量干涉研究
Confined drying of a binary liquid mixture droplet: A quantitative interferometric study under humidity control
AI总结：
本研究通过干涉仪和湿度控制实验，揭示了二元液体混合物在受限条件下的干燥动力学和传输机制，提取了浓度依赖的扩散系数和水的化学活性。
摘要：
我们提出了一种方法，结合了马奇-泽赫纳干涉仪、定制的相对湿度（RH）控制室和受限的二维液滴几何结构，以实现对复杂流体干燥及其相关传输机制的精确研究。该方法应用于一个模型二元混合物，即水-甘油混合物，其浓度依赖的热力学和传输性质相对较为明确。高分辨率干涉成像（6 μm/pixel，1帧/秒）允许同时测量干燥动力学和内部浓度场，精度为±0.5%，在此范围内广泛覆盖RH（25-95%）以及由此产生的佩克数。实验结果与一个准稳态、等温模型紧密吻合，该模型描述了由蒸汽扩散控制的蒸发与液滴内的扩散耦合。这些数据使我们能够提取出浓度依赖的相互扩散系数D(φ)和水的化学活性a_w(φ)，几乎在整个甘油体积分数φ范围内，甚至从单个低RH实验中也能提取。虽然a_w(φ)与文献值相符，但我们的测量结果为D(φ)提供了一致的拟合。补充的荧光显微镜实验证实了浮力驱动的对流虽然存在，但仍然可以忽略不计，因此在该受限几何结构中，质量扩散主导了溶质的传输。总体的一致性验证了该方法，证明了其作为定量框架研究复杂流体干燥动力学和传输的鲁棒性，具有广泛应用于受控蒸发研究的适用性。
英文摘要：
We present a methodology that combines Mach-Zehnder interferometry, a custom relative humidity (RH) controlled chamber, and a confined two-dimensional droplet geometry to enable precise investigations of drying of complex fluids and the associated transport mechanisms. This approach is applied to a model binary mixture, water-glycerol, the concentration-dependent thermodynamic and transport properties of which are relatively well documented. High-resolution interferometric imaging (6 $μ$m pixel$^{-1}$, 1 frame s$^{-1}$) allows simultaneous measurement of drying kinetics and internal concentration fields with $\pm 0.5\%$ accuracy, characterized here over a wide range of RH (25-95%), and thus Péclet numbers. The experimental results closely match a quasisteady, isothermal model of vapor-diffusion-controlled evaporation coupled to diffusion within the droplet. These data enable extraction of both the concentration-dependent mutual diffusion coefficient $D(φ)$ and the water chemical activity $a_w(φ)$ over almost the entire range of glycerol volume fraction $φ$, even from a single low-RH experiment. While $a_w(φ)$ agrees well with literature values, our measurements yield a consistent fit for $D(φ)$. Complementary experiments with fluorescence microscopy confirm that buoyancy-driven convection, although present, remains negligible, so that mass diffusion dominates solute transport in this confined geometry. The overall agreement validates the methodology, demonstrating its robustness as a quantitative framework for probing drying dynamics and transport in complex fluids, with broad applicability to controlled evaporation studies.
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