Confined drying of a binary liquid mixture droplet: A quantitative interferometric study under humidity control
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arXiv
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2026
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| author | Milark, Ole Salmon, Jean-Baptiste Sobac, Benjamin |
| author_facet | Milark, Ole Salmon, Jean-Baptiste Sobac, Benjamin |
| contents | 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_06282 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Confined drying of a binary liquid mixture droplet: A quantitative interferometric study under humidity control Milark, Ole Salmon, Jean-Baptiste Sobac, Benjamin Fluid Dynamics Soft Condensed Matter 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. |
| title | Confined drying of a binary liquid mixture droplet: A quantitative interferometric study under humidity control |
| topic | Fluid Dynamics Soft Condensed Matter |
| url | https://arxiv.org/abs/2603.06282 |