Microfabricated in-chip magnetic tweezers for intra-embryonic measurement

This paper presents a microfabricated in-chip magnetic tweezer system capable of navigating a microbead three-dimensionally and performing mechanical measurement on cell structures inside a mouse embryo. Magnetic force was modeled and experimentally calibrated. The system generates a high gradient field at the sharp pole tips and is capable of producing magnetic forces up to 120 pN with a resolution better than 2 pN. The system was used to apply tens of pN forces to multiple locations on the inner cell mass of individual mouse embryos. The results indicate that the middle region of the inner cell mass has a significantly lower stiffness than the side regions.