Low-frequency rotating and alternating magnetic field generators for biological applications: Design details of home-made setups

We describe a setup able to generate a rotating or alternating low-frequency (up to 10 Hz) magnetic field (up to 120 mT) for biological applications inside a 6 cm in diameter and 5 cm in height cylindrical space. It is suitable to insert several Petri dishes for cell death experiments and mice for in vivo ones. Since a particular attention was given to the field homogeneity, it is based on a six-pole electromagnet. The characteristics of the field are changed by varying the phase, amplitude or frequency of the electrical currents going through the coils, using a micro-controller-based human–machine interface and a RL chopper, which is described. The results of the magnetic simulations run to optimize the global design are provided. The cooling of the electromagnet is done using a chiller, and the sample temperature regulation using an air blower. All details on the mechanical, electrical and electronic elements, on the mounting, and on the programing are provided, so the setup can be reproduced. Suggestions for a further improvement of the electrical efficiency are given. This setup has already been used to demonstrate the possibility to kill cells using targeted magnetic nanoparticles and low-frequency magnetic fields.