Intraocular MEMS Capacitive Pressure Sensor

Abstract

Microelectromechanical system (MEMS) sensors are suitable for measuring intraocular pressure (IOP). IOP measurement is useful for monitoring diseases such as glaucoma. The average pressure range for healthy persons is within 10–20 mmHg. A pressure beyond this range could damage the eye nerves and causes of blindness. Thus, a sensor for measuring the pressure should provide excellent accuracy and sensitivity. Intraocular capacitive pressure sensors are widely used in measurement of IOP. They offer high sensitivity and low noise, including invariance to temperature. Thus, the capacitive pressure sensor is performed better than other types of sensing methods. In this work, capacitive pressure sensors are designed and analyzed using FEM. The sensitivity and performance of a corrugated diaphragm, slot-type, square, and circular types of sensors designed are analyzed. Different shape of the sensor provides a different characteristic such as sensors pressure sensitivity, mechanical stress, and maximum deflection. As a result, corrugated diaphragm and slot-type sensors designed performs better than the flat diaphragm and non-slotted sensors designed. We show that four slotted non-corrugated square and circular designs have a high sensitivity, which is 0.157 mF higher than the eight slotted design. However, for corrugated design, eight slotted shows sensitivity is 0.147 mF higher and linearity analysis than four slotted sensor design. Circular shape design for eight slotted design, on the other hand, have 0.631 mF higher than the four slotted design. Corrugated design is more sensitive when a load is applied, while slotted design reduces the effect of residual stress and stiffness of the diaphragm. Thus, it is an advantage of using the FEM method for further analysis of sensor performance optimization.KeywordsMEMS capacitive pressure sensorIntraocular pressure