Three-dimensional robotic control of a 5-micrometer magnetic bead for intra-embryonic navigation and measurement

Abstract

Magnetic micromanipulation has the advantage of untethered control, high precision, and biocompatibility and has recently undergone great advances. The magnetic micromanipulation task to tackle in this work is to three-dimensionally navigate a 5-micrometer magnetic bead inside a mouse embryo and perform mechanical measurements at multiple locations. Existing technologies are not able to achieve these navigation and measurement goals because of poor magnetic force scaling and/or lacking the capability of applying an accurately controlled force. This paper reports a robotic magnetic tweezer system that enables, for the first time, intra- embryonic magnetic navigation and force application. A single magnetic bead was introduced into a mouse embryo via robotic microinjection. The robotic magnetic tweezer system accurately controls the position of the magnetic bead via visually servoed magnetic control. The system is also capable of applying forces up to 120 pN with a resolution of 1.78 pN for performing mechanical measurements on the cellular structures inside the mouse embryo, revealing that the middle region is more deformable than the side regions of the inner cell mass.