Design And Simulation Of A2-D Electromagnetic Tweezers Apparatus

Magnetic tweezers (MT) utilize external magnetic field gradient to exert magnetic forces on magnetic particles in the workspace, and then manipulate the biological samples attached to the particles. Compared with other techniques such as AFM. glass microneedles, optical tweezers etc, MT have been successfully used in many biological fields with better measurement and manipulation, simple device, no mechanical invasiveness and photo damage. Moreover, magnetic forces can be applied specifically to the magnetic particles without unnecessary capture, because typical biological materials are hardly magnetic susceptible. These features make MT have a very high application value in the field of biology. The following researches have been done in this paper:Firstly, the structure, characteristics of the magnetic tweezers system are introduced. The magnetic circuit is emphatically introduced, which is a core part of the MT system. Two kinds of schemes to generate magnetic field are given and their characteristics are analyzed, respectively. Electromagnetic circuit is selected for MT device design.Secondly, A quadrupole electromagnetic tweezers system is designed for the manipulation experiment on biological samples, which is capable of exerting magnetic forces in arbitrary2-D directions on magnetic particles in the vertical plane. Based on3-D modeling of Solidworks and the foundation of electromagnet, geometry of the electromagnetic actuator system is designed, selection and processing of the device’s material is introduced. Using the high-current power amplifiers OPA548, four channel voltage-controlled constant current sources are design to drive coils. Magnetic field, magnetic circuit and magnetic force of the actuator are analyzed, respectively. Employing magnetic monopole approximation and the principle of superposition, a theoretical model is developed for describing the magnetic field produced by the system and the magnetic force exerting on the magnetic particle, then further analysis of the force model is carried out for simplifying deduction.Finally, with ANSYS, the3-D static numerical simulations of the quadrupole electromagnetic actuator system has been performed. The relationship between circuit reluctance and magnetic field is analyzed. The system structure is optimized to reduce the coil-heating problem and improve the system performance. The gradient magnetic field’s generation and control of the optimized device are demonstrated. Through AN SYS simulation, the functional relationship between the effective drive currents and the force balanced position of magnetic bead is corrected for accurately describing our designed device. The simulation results prove that this apparatus can generate2-D magnetic force in the vertical plane and apply linear displacement control to stable magnetic bead to the desired position around the center of the workspace by controlling the standardized coil current.