Azimi Yancheshme Amir, Palmese Giuseppe R, Alvarez Nicolas J
Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
Langmuir. 2023 Aug 1;39(30):10495-10503. doi: 10.1021/acs.langmuir.3c00973. Epub 2023 Jul 20.
The spreading of liquid filaments on solid surfaces is of paramount importance to a wide range of applications including ink-jet printing, coating, and direct ink writing (DIW). However, there is a considerable lack of experimental, numerical, and theoretical studies on the spreading of filaments on solid substrates. In this work, we studied the dynamics of spreading of Newtonian filaments via experiment, numerical simulations, and theoretical analysis. More specifically, we used a novel experimental setup to validate a 2D moving mesh computational fluid dynamics (CFD) model. The CFD model is used to determine the effect of processing and fluid parameters on the dynamics of filament spreading. We experimentally showed that for a Newtonian filament, the same spreading dynamics and final shape are obtained when the initial radius is constant, independent of the magnitude in printing parameters. In other words, the only important parameter on the spreading of filaments is the initial filament radius. Using a numerical model, we showed that the initial filament radius manifests itself in two important dimensionless parameters, Bond number, Bo, and viscous timescale, τ. Furthermore, the results clearly show that the dynamics of spreading are governed by the static advancing contact angle, θ. These three parameters determine a master spreading curve that can be used to predict the spreading of cylindrical filaments on flat substrates. Finally, we developed a theoretical model that was parameterized using experimental data to correlate the steady-state shape of filaments with Bo and θ. These results are particularly applicable for predicting and controlling the dynamics of filaments in DIW and other extrusion-based processes.
液体细丝在固体表面的铺展对于包括喷墨打印、涂层和直接墨水书写（DIW）在内的广泛应用至关重要。然而，目前关于细丝在固体基底上的铺展，在实验、数值模拟和理论研究方面都存在相当大的不足。在这项工作中，我们通过实验、数值模拟和理论分析研究了牛顿流体细丝的铺展动力学。更具体地说，我们使用了一种新颖的实验装置来验证二维移动网格计算流体动力学（CFD）模型。该CFD模型用于确定工艺参数和流体参数对细丝铺展动力学的影响。我们通过实验表明，对于牛顿流体细丝，当初始半径恒定时，无论打印参数的大小如何，都会获得相同的铺展动力学和最终形状。换句话说，细丝铺展中唯一重要的参数是初始细丝半径。通过数值模型，我们表明初始细丝半径体现在两个重要的无量纲参数中，即邦德数（Bo）和粘性时间尺度（τ）。此外，结果清楚地表明，铺展动力学受静态前进接触角（θ）控制。这三个参数确定了一条主铺展曲线，可用于预测圆柱形细丝在平坦基底上的铺展。最后，我们开发了一个理论模型，该模型使用实验数据进行参数化，以将细丝的稳态形状与Bo和θ相关联。这些结果特别适用于预测和控制DIW及其他基于挤压的工艺中细丝的动力学。
