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Wall fluidization in two acts: from stiff to soft roughness†
Soft Matter ( IF 2.9 ) Pub Date : 2018-01-02 00:00:00 , DOI: 10.1039/c7sm02093g Ladislav Derzsi 1, 2, 3, 4 , Daniele Filippi 1, 2, 3, 4 , Matteo Lulli 4, 5, 6, 7 , Giampaolo Mistura 1, 2, 3, 4 , Massimo Bernaschi 4, 8, 9 , Piotr Garstecki 10, 11, 12 , Mauro Sbragaglia 4, 5, 6, 7 , Matteo Pierno 1, 2, 3, 4
Soft Matter ( IF 2.9 ) Pub Date : 2018-01-02 00:00:00 , DOI: 10.1039/c7sm02093g Ladislav Derzsi 1, 2, 3, 4 , Daniele Filippi 1, 2, 3, 4 , Matteo Lulli 4, 5, 6, 7 , Giampaolo Mistura 1, 2, 3, 4 , Massimo Bernaschi 4, 8, 9 , Piotr Garstecki 10, 11, 12 , Mauro Sbragaglia 4, 5, 6, 7 , Matteo Pierno 1, 2, 3, 4
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Fluidization of soft glassy materials (SGMs) in microfluidic channels is affected by the wall roughness in the form of microtexturing. When SGMs flow across microgrooves, their constituents are likely trapped within the grooves' gap, and the way they are released locally modifies the fluidization close to the walls. By leveraging a suitable combination of experiments and numerical simulations on concentrated emulsions (a model SGM), we quantitatively report the existence of two physically different scenarios. When the gap is large compared to the droplets in the emulsion, the droplets hit the solid obstacles and easily escape scrambling with their neighbors. Conversely, as the gap spacing is reduced, droplets get trapped inside, creating a “soft roughness” layer, i.e. a complementary series of deformable posts from which overlying droplets are in turn released. In both cases, the induced fluidization scales with the grooves' density, although with a reduced prefactor for narrow gaps, accounting for the softness of the roughness. Both scenarios are also well distinguished via the statistics of the droplets displacement field close to the walls, with large deviations induced by the surface roughness, depending on its stiffness.
中文翻译：
墙体流化有两种作用：从坚硬到软粗糙度†
微玻璃通道中软玻璃质材料（SGM）的流化受微纹理形式的壁面粗糙度的影响。当SGM穿过微沟槽时，它们的成分很可能被困在凹槽的间隙内，它们被局部释放的方式改变了靠近壁的流化状态。通过对浓乳液（模型SGM）进行适当的实验和数值模拟相结合，我们定量报告了两种物理上不同的情况的存在。与乳剂中的液滴相比，当间隙大时，液滴会撞到固体障碍物，并容易逃脱与邻居的争夺。相反，随着间隙间距的减小，液滴会被困在内部，从而形成“软粗糙度”层，即一系列互补的可变形柱，依次释放覆盖的液滴。在这两种情况下，诱导的流化程度均随沟槽的密度而变化，尽管狭窄缝隙的系数减小了，这说明了粗糙度的柔软性。通过对靠近壁的液滴位移场的统计也可以很好地区分这两种情况，取决于其刚度，表面粗糙度会引起较大的偏差。
更新日期：2018-01-02
中文翻译：
墙体流化有两种作用：从坚硬到软粗糙度†
微玻璃通道中软玻璃质材料（SGM）的流化受微纹理形式的壁面粗糙度的影响。当SGM穿过微沟槽时，它们的成分很可能被困在凹槽的间隙内，它们被局部释放的方式改变了靠近壁的流化状态。通过对浓乳液（模型SGM）进行适当的实验和数值模拟相结合，我们定量报告了两种物理上不同的情况的存在。与乳剂中的液滴相比，当间隙大时，液滴会撞到固体障碍物，并容易逃脱与邻居的争夺。相反，随着间隙间距的减小，液滴会被困在内部，从而形成“软粗糙度”层，即一系列互补的可变形柱，依次释放覆盖的液滴。在这两种情况下，诱导的流化程度均随沟槽的密度而变化，尽管狭窄缝隙的系数减小了，这说明了粗糙度的柔软性。通过对靠近壁的液滴位移场的统计也可以很好地区分这两种情况，取决于其刚度，表面粗糙度会引起较大的偏差。
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