Magnetic Resonance Imaging (MRI) is a powerful tool for the diagnosis and the monitoring of diseases in the frame of research models developed on small animal in neurosciences. This application requires a high spatial resolution and a high Signal to Noise Ratio (SNR) using a high magnetic field (7 T) and a highly sensitive miniaturized coil, implanted near the interest area. The coilmonolithic design, called Multi-turn Transmission Lines Resonator (MTLR), allows theminiaturization below the centimeter scale and the clean-room technology. To reduce the invasive aspect of implantation, the coil was fabricated on a flexible substrate: FEP Teflon® or PDMS. To overcome adhesion issues related to these polymers, specific plasma treatments were applied to FEPTeflon® while a transfer process dedicated to PDMS was developed. Besides mechanical reliability, the thickness of the PDMS coating ensuring the coil biocompatibility, was optimized to limit the dielectric coupling with tissues and thus to keep suitable electromagnetic characteristics for 7 T MRI when the coil is implanted. This work allowed the achievement of the first images of the rat brain acquired in vivo using an implanted soft coil. These images have shown a 5-fold enhanced SNRcompared with the ones acquired using a commercial quadrature coil. Other applications in the biomedical field are open by this work: sensors for the dielectric characterization of tissues, integrated microcoils and pressure sensors in microfluidic channels.
