Micro Helmholtz coil pair towards cellular applications

Introduction Micro Helmholtz coils are needed in medical technology for high-resolution magnetic resonance imaging (MRI) or for nuclear magnetic resonance (NMR) spectroscopy at the micro level. The coil sensitivity, and therefore the desired signal, is maximized when the size of the coil matches that of the sample [1, 2]. Small sample analysis with micro Helmholtz coils shows exceptional performance compared to planar coils and allows for advanced chemical analysis. Due to their 3-D shape, the B1unit field is stronger and more uniform [3]. Among NMR applications, modified micro Helmholtz coils (Maxwell coils) are used for the creation of high magnetic field gradients [4, 5]. So far, difficult 3-D processes prevent the production of suitable coils and only few publications exist. Up to 10 process steps [3] or coils made by hand [4] are insufficient for reproducible coils and make successful measurements very difficult or impossible. As devices are often single use, low-cost solutions are most promising. We present Helmholtz coils made with a wire bonder with included sample containers in microliter range, which are cheap and reproducible in a mass production sense.