Abstract
Bio-MEMS devices have been made for separating and manipulating magnetic particles in recent years. The possibility of combining the thoughts of cell separation and accurately position of cells have been proved. In this article, an approach is described for controlling the alignment of cells by using superparamagnetic beads and patterned magnetic film arrays. We designed multilayer magnetic films to develop a simple and cheap cell patterning method. The zigzag multilayer magnetic films were made by photolithography, and the resolution of the lithography system was shown to be more than 3 µm. The line width is 5 µm. After the magnetic films are magnetized, we use the remanent states of the planar magnetic microstructures without continuously applying magnetic field. Distinct domain structures are available, when we changing the orientation of magnetic field, because of the zigzag geometry of magnetic films. Then, we measured the thickness of magnetic films and the distributions of domain walls by using magnetic force microscopy. We labeled human nasopharyngeal carcinoma cells by using magnetic nanoparticles, and quantified the magnetic nanoparticles within cells by using magnetophoresis .After dropping the magnetic nanoparticles-labeled cells upon magnetic films, we found that the gradient of stray field which generated by domain walls results in an attractive force acting on magnetic nanoparticles-labeled cells and the cells translocated in the proximity of the domain wall location. By measuring the distance between cell location and the sites of domain walls, the results prove that the magnetic nanoparticles-labeled cells can be manipulated by domain walls, and the patterns of cells in two dimensions are formed orderly. Based on this, we improved the shortcoming of traditional cell patterning devices, which must be continuously applying magnetic field when using magnetic force. We believed that this method is a potential tool for several applications including single molecule manipulation, biomagnetic sensing and cell-cell interaction. Such a method would open up new possibility of lab-on-chip application.