Sahu Dinesh Kumar, Dhara Surajit
School of Physics, University of Hyderabad, Hyderabad 500 046, India.
Soft Matter. 2022 Mar 2;18(9):1819-1824. doi: 10.1039/d1sm01653a.
We study the electrophoresis of metal-dielectric Janus particles with dipolar director symmetry in two nematic liquid crystals (LCs) having the same sign of conductivity anisotropy (Δ) but opposite signs of dielectric anisotropy (Δ). The applied ac electric field is parallel and perpendicular to the director for positive and negative dielectric anisotropy LCs, respectively. We show that the Janus dipolar particles propel faster than the non-Janus dipolar particles in both LCs. The propelling speed of the Janus dipolar particles is also significantly higher compared to the quadrupolar Janus particles studied previously. We map the electroosmotic flow fields surrounding a Janus dipolar particle using microparticle image velocimetry (μ-PIV) and show that the flow on a metal hemisphere is stronger than that on a dielectric hemisphere. Altogether, Janus dipolar particles demonstrate efficient electrophoresis compared to both Janus and non-Janus quadrupolar particles. These findings may be useful for applications in active matter, microrobotic and microfluidic devices.
我们研究了具有偶极指向矢对称性的金属 - 电介质 Janus 粒子在两种向列型液晶（LC）中的电泳行为，这两种液晶具有相同符号的电导率各向异性（Δ）但相反符号的介电各向异性（Δ）。对于正介电各向异性和负介电各向异性的液晶，施加的交流电场分别平行和垂直于指向矢。我们表明，在两种液晶中，Janus 偶极粒子的推进速度都比非 Janus 偶极粒子快。与先前研究的四极 Janus 粒子相比，Janus 偶极粒子的推进速度也显著更高。我们使用微粒图像测速技术（μ - PIV）绘制了 Janus 偶极粒子周围的电渗流场，并表明金属半球上的流动比电介质半球上的流动更强。总体而言，与 Janus 和非 Janus 四极粒子相比，Janus 偶极粒子表现出高效的电泳。这些发现可能对活性物质、微型机器人和微流控设备中的应用有用。
