Increasing sensing distance of passive wireless IOP sensor

Continuous intraocular pressure monitoring is very necessary for glaucoma patients. In this paper, a passive wireless intraocular pressure (IOP) sensor using an inductively coupled wireless sensing technique is presented. IOP sensor is consist of a multipath circular spiral coil inductor, variable capacitor and a SU-8 pressure sensitive diaphragm. Capacitor and inductor of sensor are made of high-conductivity and biocompatible metal gold that are encapsulated inside biocompatible SU-8 to prevent damage to eye tissue. By measuring impedance phase dip frequency shift from the external reader coil, the intraocular pressure signal is obtained from the IOP sensor. Small size of the sensor coil due to the biological constrains reduces the sensing distance. The purpose of this paper is increasing the quality factor of sensor coil using the multipath technique in order to enhancement of sensing distance. Simulation has been taken using COMSOL Multiphysics and ADS software. The proposed structure, due to its small size could increase the sensing distance. The dimension of proposed wireless sensor and sensing distance is \( 2.5\;{\text{mm }} \times 2.5\;{\text{mm}} \) and 2 cm, respectively, that has a larger sensing distance and smaller size compared with previous works and its sensitivity is 4281 ppm/mmHg.