Basic characteristics of implantable flexible pressure sensor for wireless readout using MRI

Measurement of pressure within blood vessels will be valuable for the diagnoses of aneurysm. However, implantation of a conventional pressure sensor equipped with power and signal cables causes difficulties in surgery and risk of infection after implantation.In this study, we developed a wireless, implantable, and flexible pressure sensor. An MRI system reads out the sensor output.The proposed wireless sensor is based on an LC resonance circuit with a spiral coil and a pressure-sensitive capacitor.The pressure-dependence of the circuit affects the fields arising from the spiral coil, changing the nearby sample magnetization, and thus can be observed as an MRI signal variation.We fabricated a prototype sensor using silicone elastomer as dielectric with gold wiring. The maximum change in the capacitance was 8% under external pressure of 20 kPa.A change in thickness of dielectric elastomer caused the capacitance change, resulting in a detectable change in MRI.