School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798.
Lab Chip. 2012 Nov 21;12(22):4772-80. doi: 10.1039/c2lc40818j.
This paper reports the investigation of mixing phenomena caused by the interaction between a uniform magnetic field and a magnetic fluid in a microfluidic chamber. The flow system consists of a water-based ferrofluid and a mixture of DI water and glycerol. Under a uniform magnetic field, the mismatch in magnetization of the fluids leads to instability at the interface and subsequent rapid mixing. The mismatch of magnetization is determined by concentration of magnetic nanoparticles. Full mixing at a relatively low magnetic flux density up to 10 mT can be achieved. The paper discusses the impact of key parameters such as magnetic flux density, flow rate ratio and viscosity ratio on the mixing efficiency. Two main mixing regimes are observed. In the improved diffusive mixing regime under low field strength, magnetic particles of the ferrofluid migrate into the diamagnetic fluid. In the bulk transport regime under high field strength, the fluid system is mixed rapidly by magnetically induced secondary flow in the chamber. The mixing concept potentially provides a wireless solution for a lab-on-a-chip system that is low-cost, robust, free of induced heat and independent of pH level or ion concentration.
本文报道了在微流腔中均匀磁场与磁流体相互作用引起的混合现象的研究。该流系统由水基铁磁流体和 DI 水与甘油的混合物组成。在均匀磁场下，由于流体的磁化率不匹配，导致界面失稳，随后迅速混合。磁化率的不匹配取决于磁性纳米粒子的浓度。在相对较低的磁通密度高达 10 mT 时可实现完全混合。本文讨论了磁通密度、流速比和粘度比等关键参数对混合效率的影响。观察到两种主要的混合模式。在低磁场强度下的改进扩散混合模式中，铁磁流体中的磁性颗粒迁移到抗磁性流体中。在高磁场强度下的体传输模式中，通过腔室内的磁致二次流快速混合流体系统。这种混合概念为低成本、坚固、无感应热且不依赖 pH 值或离子浓度的片上实验室系统提供了一种无线解决方案。
