Magnetophoresis, the manipulation of trajectory of micro-scale entities using magnetic forces, as employed in microfluidic devices is reviewed at length in this article. Magnetophoresis has recently garnered significant interest due to its simplicity, in terms of implementation, as well as cost-effectiveness while being efficient and biocompatible. Theory associated with magnetophoresis is illustrated in this review along with different sources for creating magnetic field gradient commonly employed in microfluidic devices. Additionally, this article reviews the state-of-the-art of magnetophoresis based microfluidic devices, where positive- and negative-magnetophoresis are utilized for manipulation of micro-scale entities (cells and microparticles), employed for operations such as trapping, focusing, separation, and switching of microparticles and cells. The article concludes with a brief outlook of the field of magnetophoresis.

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We describe the design, microfabrication, and testing of a microfluidic device for the separation of cancer cells based on dielectrophoresis. Cancer cells, specifically green fluorescent protein-labeled MDA-MB-231, are successfully separated from a heterogeneous mixture of the same and normal blood cells. MDA-MB-231 cancer cells are separated with an accuracy that enables precise detection and counting of circulating tumor cells present among normal blood cells. The separation is performed using a set of planar interdigitated transducer electrodes that are deposited on the surface of a glass wafer and slightly protrude into the separation microchannel at one side. The device includes two parts, namely, a glass wafer and polydimethylsiloxane element. The device is fabricated using standard microfabrication techniques. All experiments are conducted with low conductivity sucrose-dextrose isotonic medium. The variation in response between MDA-MB-231 cancer cells and normal cells to a certain band of alternating-current frequencies is used for continuous separation of cells. The fabrication of the microfluidic device, preparation of cells and medium, and flow conditions are detailed. The proposed microdevice can be used to detect and separate malignant cells from heterogeneous mixture of cells for the purpose of early screening for cancer.

High seroprevalence rates for Anaplasma phagocytophilum (8.8%), Coxiella burnetii (6.4%), Bartonella henselae (9.6%), and Rickettsia typhi (4.1%) in 365 farm workers near Tianjin, People’s Republic of China, suggest that human infections with these zoonotic bacteria are frequent and largely unrecognized. Demographic features of seropositive persons suggest distinct epidemiology, ecology, and risks.