微结构阵列对近壁面层液体运动规律的影响
|
摘要
表面微结构阵列可用于调控微间隙中液体的流动行为、运动阻力和混合特性等.本文采用石英晶体微天平实验研究了微凹坑和微圆柱阵列以及微结构表面形貌对近壁面层液体运动行为的影响.石英晶体微天平的系统频移和半带宽变化与近壁面层液体的运动行为密切相关,研究显示,表面微凹坑倾向于受限液体的运动,因此微凹坑表面引起的频移绝对值明显大于与其具有相同特征尺寸的微圆柱表面,且均大于光滑表面.粗糙表面结构会明显地增加近壁面区域液体运动的紊乱程度,因此具有粗糙顶部的二级微圆柱表面引起的半带宽变化明显大于与其具有相同特征尺寸的微圆柱表面,且均大于光滑表面.该研究为微流道表面阵列微结构形式的选择提供了实验依据.
Study of the liquid flowing behavior through the micro-structure array has aroused the significant interest due to its key roles in the fields of microfluidics, micro-mixers, micro-heat exchangers, tribology, etc. Micro-structure array can significantly affect the liquid flowing characteristics of the near-surface layer and the solid-liquid interfacial properties,like adhesion, surface wetting, shear viscous resistance, interfacial slip, etc. The researches indicate that the stripe- and square-patterned electrodes can improve the storage properties of the lithium-ion battery due to its ability to promote the diffusion of the liquid electrolyte. Micro-structure array patterned micro-channel can reduce the friction drag of liquid flowing through it. And the surface fabricated with lotus-leaf-like dual-scale structure array can achieve the superhydrophobicity.For a micro-structure array, its in?uences on the liquid ?owing behaviors greatly depend on the shape and size of the micro-structure, and the porosity, arrangement and size of the array. Here, we mainly focus on the in?uences of the micro-structure shape and surface topography on the liquid ?owing behaviors, by adopting the same array porosity,arrangement and size, and the same feature size of the micro-structure. In the present paper, we prepare three different surfaces, which are the micro-pillar array surfaces, micro-hole array surface, and dual-scale micro-pillar array surface(i.e., micro-pillar with rough top surface), respectively. Their in?uences on the liquid ?owing characteristics of the nearsurface layer are investigated by quartz crystal microbalance(QCM). The QCM is a powerful and promising technique in studying the solid/liquid interfacial behaviors. Its main output parameters are frequency shift and half-bandwidth variation, which are closely related to the rheological properties and ?ow characteristics of the near-surface liquid layer.When the QCM chip is patterned with micro-structure array, it will inevitably in?uence the liquid motion and makes it more complicated, like the generation of non-laminar motion, the trapping of liquid in the gap, and the conversion of the in-plane surface motion into the surface-normal liquid motion. The experimental results show that for the same tested liquid, the frequency shift caused by the micro-hole array is higher than that by the micro-pillar array with the same feature size. And the dual-scale micro-pillar array surface results in a higher half-bandwidth variation than the micro-pillar array surface with the same feature size. It demonstrates that micro-hole tends to con?ne the liquid motion and make the trapped liquid oscillate with the substrate like a rigid ?lm, thus resulting in a higher frequency shift. The dual-scale micro-structure will render the ?ow behavior of the near-surface layer more chaotic, thus showing a larger half-bandwidth variation. This study provides an experimental basis for selecting the type of micro-structure used in the micro?uidic chip to better control the liquid ?owing and mixing.
Study of the liquid flowing behavior through the micro-structure array has aroused the significant interest due to its key roles in the fields of microfluidics, micro-mixers, micro-heat exchangers, tribology, etc. Micro-structure array can significantly affect the liquid flowing characteristics of the near-surface layer and the solid-liquid interfacial properties,like adhesion, surface wetting, shear viscous resistance, interfacial slip, etc. The researches indicate that the stripe- and square-patterned electrodes can improve the storage properties of the lithium-ion battery due to its ability to promote the diffusion of the liquid electrolyte. Micro-structure array patterned micro-channel can reduce the friction drag of liquid flowing through it. And the surface fabricated with lotus-leaf-like dual-scale structure array can achieve the superhydrophobicity.For a micro-structure array, its in?uences on the liquid ?owing behaviors greatly depend on the shape and size of the micro-structure, and the porosity, arrangement and size of the array. Here, we mainly focus on the in?uences of the micro-structure shape and surface topography on the liquid ?owing behaviors, by adopting the same array porosity,arrangement and size, and the same feature size of the micro-structure. In the present paper, we prepare three different surfaces, which are the micro-pillar array surfaces, micro-hole array surface, and dual-scale micro-pillar array surface(i.e., micro-pillar with rough top surface), respectively. Their in?uences on the liquid ?owing characteristics of the nearsurface layer are investigated by quartz crystal microbalance(QCM). The QCM is a powerful and promising technique in studying the solid/liquid interfacial behaviors. Its main output parameters are frequency shift and half-bandwidth variation, which are closely related to the rheological properties and ?ow characteristics of the near-surface liquid layer.When the QCM chip is patterned with micro-structure array, it will inevitably in?uence the liquid motion and makes it more complicated, like the generation of non-laminar motion, the trapping of liquid in the gap, and the conversion of the in-plane surface motion into the surface-normal liquid motion. The experimental results show that for the same tested liquid, the frequency shift caused by the micro-hole array is higher than that by the micro-pillar array with the same feature size. And the dual-scale micro-pillar array surface results in a higher half-bandwidth variation than the micro-pillar array surface with the same feature size. It demonstrates that micro-hole tends to con?ne the liquid motion and make the trapped liquid oscillate with the substrate like a rigid ?lm, thus resulting in a higher frequency shift. The dual-scale micro-structure will render the ?ow behavior of the near-surface layer more chaotic, thus showing a larger half-bandwidth variation. This study provides an experimental basis for selecting the type of micro-structure used in the micro?uidic chip to better control the liquid ?owing and mixing.
引文
[1]Darbois Texier B,Laurent P,Stoukatch S,Dorbolo S2016 Microfluid.Nanofluid 20 53
[2]Yamada T,Hong C,Gregory O J,Faghri M 2011 Microfluid Nanofluid.11 45
[3]Gu Y,Zhao G,Zheng J,Li Z,Liu W,Muhammad F K2014 Ocean Eng.81 50
[4]Lyu S,Nguyen D C,Kim D,Hwang W,Yoon B 2013Appl.Surf.Sci.286 206
[5]Jung Y C,Bhushan B 2010 J.Phys.Condens.Matter:Instit.Phys.J.22 35104
[6]Woolford B,Prince J,Maynes D,Webb B W 2009 Phys.Fluids 21 85106
[7]Ou J,Perot B,Rothstein J P 2004 Phys.Fluids 16 4635
[8]Lee S H,Kim W B 2016 J.Power Sources 307 38
[9]Goullet A,Glasgow I,Aubry N 2006 Mech.Res.Commun.33 739
[10]Priezjev N V 2011 J.Chem.Phys.135 204704
[11]Suh M,Chae Y,Kim S,Hinoki T,Kohyama A 2010Tribol.Int.43 1508
[12]Mills A,Burns L,Rourke C O,Madsen H 2016 Sol.Energ.Mat.Sol.C 144 78
[13]Rechendorff K,Hovgaard M B,Foss M,Besenbacher F2007 J.Appl.Phys.101 114502
[14]Daikhin L,Gileadi E,Katz G,Tsionsky V,Urbakh M,Zagidulin D 2002 Anal.Chem.74 554
[15]Levi M D,Daikhin L,Aurbach D,Presser V 2016 Electrochem.Commun.67 16
[16]Daikhin L,Urbakh M 1996 Langmuir 12 6354
[2]Yamada T,Hong C,Gregory O J,Faghri M 2011 Microfluid Nanofluid.11 45
[3]Gu Y,Zhao G,Zheng J,Li Z,Liu W,Muhammad F K2014 Ocean Eng.81 50
[4]Lyu S,Nguyen D C,Kim D,Hwang W,Yoon B 2013Appl.Surf.Sci.286 206
[5]Jung Y C,Bhushan B 2010 J.Phys.Condens.Matter:Instit.Phys.J.22 35104
[6]Woolford B,Prince J,Maynes D,Webb B W 2009 Phys.Fluids 21 85106
[7]Ou J,Perot B,Rothstein J P 2004 Phys.Fluids 16 4635
[8]Lee S H,Kim W B 2016 J.Power Sources 307 38
[9]Goullet A,Glasgow I,Aubry N 2006 Mech.Res.Commun.33 739
[10]Priezjev N V 2011 J.Chem.Phys.135 204704
[11]Suh M,Chae Y,Kim S,Hinoki T,Kohyama A 2010Tribol.Int.43 1508
[12]Mills A,Burns L,Rourke C O,Madsen H 2016 Sol.Energ.Mat.Sol.C 144 78
[13]Rechendorff K,Hovgaard M B,Foss M,Besenbacher F2007 J.Appl.Phys.101 114502
[14]Daikhin L,Gileadi E,Katz G,Tsionsky V,Urbakh M,Zagidulin D 2002 Anal.Chem.74 554
[15]Levi M D,Daikhin L,Aurbach D,Presser V 2016 Electrochem.Commun.67 16
[16]Daikhin L,Urbakh M 1996 Langmuir 12 6354