We employ a state-of-the-art microfabrication technique (selective laser-induced etching) to fabricate a set of axisymmetric microfluidic geometries featuring a 4:1 contraction followed by a 1:4 downstream expansion in the radial dimension. Three devices are fabricated: the first has a sudden contraction followed by a sudden expansion, the second features hyperbolic contraction and expansion profiles, and the third has a numerically optimized contraction/expansion profile intended to provide a constant extensional/compressional rate along the axis. We use micro-particle image velocimetry to study the creeping flow of a Newtonian fluid through the three devices and we compare the obtained velocity profiles with finite-volume numerical predictions, with good agreement. This work demonstrates the capability of this new microfabrication technique for producing accurate non-planar microfluidic geometries with complex shapes and with sufficient clarity for optical probes. The axisymmetric microfluidic geometries examined have potential to be used for the study of the extensional properties and non-linear dynamics of viscoelastic flows, and to investigate the transport and deformation dynamics of bubbles, drops, cells, and fibers.

中文翻译：

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通过微加工的轴对称收缩/膨胀几何形状的粘性流动

我们采用最先进的微制造技术（选择性激光诱导蚀刻）来制造一组轴对称微流体几何形状，其特征是 4:1 收缩，然后是 1:4 的径向尺寸下游膨胀。制造了三个设备：第一个具有突然收缩，然后是突然膨胀，第二个具有双曲线收缩和膨胀曲线，第三个具有数值优化的收缩/膨胀曲线，旨在提供沿轴的恒定拉伸/压缩率。我们使用微粒图像测速来研究牛顿流体通过三个装置的蠕动，并将获得的速度剖面与有限体积数值预测进行比较，结果非常吻合。这项工作证明了这种新的微细加工技术能够生产具有复杂形状的精确非平面微流体几何形状，并且具有足够的光学探针清晰度。检查的轴对称微流体几何结构有可能用于研究粘弹性流动的拉伸特性和非线性动力学，以及研究气泡、液滴、细胞和纤维的传输和变形动力学。