Ghosh Udita Uday, Dhara Trina, Bakshi Janesh, Nath Kalpita, DasGupta Sunando
Department of Chemical Engineering and Technology, Indian Institute of Technology (BHU), Varanasi 221005, India.
Department of Chemical Engineering, Indian Institute of Technology, Kharagpur 721302, India.
Biomicrofluidics. 2024 Oct 2;18(5):054108. doi: 10.1063/5.0209815. eCollection 2024 Sep.
The physics of the effects of electric field on the desiccation of colloidal droplets, comprising of dispersed negatively charged nanoparticles [2 l, 1(w/w. %)], are studied in a standard electrowetting-on-a-dielectric configuration. The extent of contact line pinning during evaporation is found to be a function of the magnitude of the applied voltage and quantified in terms of the dimensionless electrowetting number (). The pinned contact line led to higher particle compaction as evidenced by the characterization of dried colloidal film thicknesses. Crack formation and their dynamics have been analyzed in detail to elicit the interplay of forces near the contact line region and on the compaction front. These aspects of crack formation are elucidated in the light of magnitude and polarity of the applied electric field. It is found to influence the crack front initiation velocity, the geometry, the number of cracks, and an attempt is made to explain the same via first principle-based approaches. Therefore, this study indicates the possibility of using electrowetting as a technique to fine-tune the crack formation behavior in thin colloidal films.
在标准的介电层上电润湿配置中，研究了电场对由分散的带负电纳米颗粒[2 l，1（重量/重量%）]组成的胶体液滴干燥的影响的物理过程。发现在蒸发过程中接触线钉扎的程度是施加电压大小的函数，并根据无量纲电润湿数（）进行量化。如干燥胶体膜厚度的表征所示，钉扎的接触线导致更高的颗粒压实。已详细分析了裂纹形成及其动力学，以揭示接触线区域附近和压实前沿的力的相互作用。根据施加电场的大小和极性阐明了裂纹形成的这些方面。发现它会影响裂纹前沿起始速度、几何形状、裂纹数量，并尝试通过基于第一原理的方法对其进行解释。因此，本研究表明了使用电润湿作为一种微调薄胶体膜中裂纹形成行为的技术的可能性。
