Department of Chemical Engineering and Materials Science, University of Minnesota - Twin Cities , 421 Washington Avenue Southeast, Minneapolis Minnesota 55455, United States.
Langmuir. 2017 Mar 28;33(12):2949-2964. doi: 10.1021/acs.langmuir.6b04506. Epub 2017 Mar 16.
Microchannels have applications in microfluidic devices, patterns for micromolding, and even flexible electronic devices. Three-dimensional (3D) printing presents a promising alternative manufacturing route for these microchannels due to the technology's relative speed and the design freedom it affords its users. However, the roughness of 3D printed surfaces can significantly influence flow dynamics inside of a microchannel. In this work, open microchannels are fabricated using four different 3D printing techniques: fused deposition modeling (FDM), stereolithography (SLA), selective laser sintering, and multi jet modeling. Microchannels printed with each technology are evaluated with respect to their surface roughness, morphology, and how conducive they are to spontaneous capillary filling. Based on this initial assessment, microchannels printed with FDM and SLA are chosen as models to study spontaneous, capillary-driven flow dynamics in 3D printed microchannels. Flow dynamics are investigated over short (∼10 s), intermediate (∼1 s), and long (∼10 s) time scales. Surface roughness causes a start-stop motion down the channel due to contact line pinning, while the cross-sectional shape imparted onto the channels during the printing process is shown to reduce the expected filling velocity. A significant delay in the onset of Lucas-Washburn dynamics (a long-time equilibrium state where meniscus position advances proportionally to the square root of time) is also observed. Flow dynamics are assessed as a function of printing technology, print orientation, channel dimensions, and liquid properties. This study provides the first in-depth investigation of the effect of 3D printing on microchannel flow dynamics as well as a set of rules on how to account for these effects in practice. The extension of these effects to closed microchannels and microchannels fabricated with other 3D printing technologies is also discussed.
微通道在微流控设备、微成型图案，甚至柔性电子设备中都有应用。由于 3D 打印技术的相对速度和为用户提供的设计自由度，它为这些微通道提供了一种有前途的替代制造途径。然而，3D 打印表面的粗糙度会显著影响微通道内的流动动力学。在这项工作中，使用四种不同的 3D 打印技术制造了开放式微通道：熔融沉积建模（FDM）、立体光刻（SLA）、选择性激光烧结和多喷射建模。根据表面粗糙度、形态以及对自发毛细填充的促进程度，评估了每种技术打印的微通道。在此初步评估的基础上，选择 FDM 和 SLA 打印的微通道作为模型，研究 3D 打印微通道中自发、毛细驱动的流动动力学。在短时间（约 10 秒）、中等时间（约 1 秒）和长时间（约 10 秒）尺度上研究了流动动力学。由于接触线钉扎，表面粗糙度导致通道内出现停走运动，而在打印过程中赋予通道的横截面形状被证明会降低预期的填充速度。还观察到 Lucas-Washburn 动力学（一种长时间平衡状态，其中弯月面位置与时间的平方根成比例前进）的起始延迟。还评估了流动动力学作为打印技术、打印方向、通道尺寸和液体性质的函数。本研究首次深入研究了 3D 打印对微通道流动动力学的影响，并提供了一套如何在实践中考虑这些影响的规则。还讨论了这些效应在封闭微通道和使用其他 3D 打印技术制造的微通道中的扩展。
