Design and optimization of a three-terminal piezoresistive pressure sensor for catheter based in vivo biomedical applications

Abstract

In recent times, catheters with integrated transducers have been extensively investigated in the field of biomedical engineering, especially for use in in vivo neonatal intensive care systems. An integral module of such systems is a blood pressure sensor that must fulfill the competing requirements of high sensitivity and small area. Typically, microelectromechanical systems-based membrane structures with integrated piezoresistors are used to realize such miniaturized blood pressure sensors. Conventionally, the electromechanical transduction of membrane deformation into an equivalent electrical signal is accomplished by piezoresistors connected in a fully active Wheatstone bridge configuration. However, such a configuration requires a large area for the placement of piezoresistors and layout of interconnects. Even though piezoresistors connected in a half-active Wheatstone bridge configuration overcome the area constraint, such an arrangement still suffers from reduced electrical sensitivity. In this paper we propose a novel three-terminal single-element piezoresistor membrane-based miniaturized blood pressure sensor for less than 1 French catheter application. Design and optimization of the sensor is performed using numerical simulations to satisfy the competing requirements of high sensitivity, low structural non-linearity and high mechanical stability. Simulations are carried out to optimize the piezoresistor position, piezoresistor doping concentration and relative dimensions of the piezoresistor and the membrane. Results depict that sensor with a die size of 175 × 150 × 50 μm3 results in an electrical sensitivity of 14.03 μA A–1 mmHg–1. Finally, a set of design guidelines are outlined for optimizing the performance of three-terminal piezoresistor-based blood pressure sensors.