Programmable Screen for Patterning Magnetic Fields

We present the design and experimental demonstration of a magnetic screen, which can pattern magnetic field into 256 programmable spots of small sub-wavelength dimension. A design methodology is outlined for designing a near-field plate to achieve a desired focus, and its implementation is discussed. Simulation using a full-wave electromagnetic solver clearly demonstrates focused magnetic field spots and that the presented structure has a stronger magnetic field compared with a conventional coil at the same focusing distance. A sample of thickness 2.1 mm with 16 layers, in which there are 32 unclosed loops for focusing on each of the eight layers and optimized guiding strips on the other eight layers, is fabricated and measured. The measurement results agree well with the simulation results. Finally, the response of the magnetic screen in the time domain is measured and computed showing the screen can be operated under pulse excitation. Such a device, capable of producing a programmable focused magnetic field, will find applications in biomedical devices, near-field imaging systems, data storage, and electromechanical actuators.