TY - JOUR
T1 - Particle distribution and velocity in electrokinetically induced banding
AU - Rossi, Massimiliano
AU - Marin, Alvaro
AU - Cevheri, Necmettin
AU - Kähler, Christian J.
AU - Yoda, Minami
PY - 2019/5/1
Y1 - 2019/5/1
N2 - Colloidal particles may be repelled from/attracted to the walls of glass micro-channels when an electro-osmotic flow is combined with a Poiseuille flow. Under certain conditions, the particles assemble into bands after accumulating near the walls (Cevheri and Yoda in Lab Chip 14(8):1391–1394, 2014). The fundamental physical mechanisms behind these phenomena remain unclear and up to now only measurements within 1μm of the walls have been available. In this work, we applied a 3D particle-tracking technique, astigmatism particle tracking velocimetry, to measure the concentration and velocity distribution of particles across the depth of the entire micro-channel. The experiments show that the particles are depleted in the bulk as they become concentrated near the bottom and top walls and this particle redistribution depends strongly upon the bulk particle concentration. The results suggest that bands form in a region where particles are practically immobile and their volume fraction increases at least an order of magnitude with respect to the original volume fraction. Our results suggest that particle accumulation and band formation near the walls may be triggered by forces generated in the bulk since the banding and particle accumulation extends at least a few μ m into the channel, or at length scales beyond the range of surface forces due to wall interactions.
AB - Colloidal particles may be repelled from/attracted to the walls of glass micro-channels when an electro-osmotic flow is combined with a Poiseuille flow. Under certain conditions, the particles assemble into bands after accumulating near the walls (Cevheri and Yoda in Lab Chip 14(8):1391–1394, 2014). The fundamental physical mechanisms behind these phenomena remain unclear and up to now only measurements within 1μm of the walls have been available. In this work, we applied a 3D particle-tracking technique, astigmatism particle tracking velocimetry, to measure the concentration and velocity distribution of particles across the depth of the entire micro-channel. The experiments show that the particles are depleted in the bulk as they become concentrated near the bottom and top walls and this particle redistribution depends strongly upon the bulk particle concentration. The results suggest that bands form in a region where particles are practically immobile and their volume fraction increases at least an order of magnitude with respect to the original volume fraction. Our results suggest that particle accumulation and band formation near the walls may be triggered by forces generated in the bulk since the banding and particle accumulation extends at least a few μ m into the channel, or at length scales beyond the range of surface forces due to wall interactions.
KW - Astigmatic-PTV
KW - Electro-osmotic flow
KW - Electrokinetic banding
KW - Micro-PIV
KW - Micro/nanoparticles
KW - Self-assembly
KW - 22/4 OA procedure
UR - http://www.scopus.com/inward/record.url?scp=85064044445&partnerID=8YFLogxK
U2 - 10.1007/s10404-019-2227-9
DO - 10.1007/s10404-019-2227-9
M3 - Article
AN - SCOPUS:85064044445
SN - 1613-4982
VL - 23
JO - Microfluidics and nanofluidics
JF - Microfluidics and nanofluidics
IS - 5
M1 - 67
ER -