Porous Elastomer Based Wide Range Flexible Pressure Sensor for Autonomous Underwater Vehicles

This work presents the design and implementation of a porous polydimethylsiloxane (PDMS)-based wide-range flexible pressure sensor for autonomous underwater vehicles. The capacitive sensor, with porous PDMS as dielectric, is encapsulated in bulk PDMS polymer. The fabricated sensor was evaluated over a wide pressure range (0-230 kPa), which is similar to pressures experienced up to approx. 23 m below the sea level. The sensors showed linear response when tested in air and near-linear response (98%) when submerged in water. The sensor showed much higher sensitivity (0.375 kPa⁻¹) in water than in the air environment. However, the sensor exhibited the performance and sensitivity similar to the air condition (0.005 kPa⁻¹) when the readout electronics (encapsulated inside a watertight enclosure) was also submerged inside the water along with the sensor. The fabricated sensor also exhibited fast response and recovery time (190 ms), as well as excellent repeatability and stability (no drift) over tested range of 50 loading and unloading cycles. These results demonstrate the suitability of presented sensors for potential use in applications requiring a wide range of pressure, particularly the underwater robotics where real-time pressure monitoring is critical for autonomous operation.

I. Introduction

Recently, there has been a growing interest in applying Autonomous underwater vehicles (AUVs) for real-time and remote monitoring of underwater environments as well as environmental inspection and surveillance operations [1], [2]. One of the most indispensable sensors found on board AUVs is the pressure sensors, which is needed to detect local pressure variations to help the AUV avoid obstacles, maintain a desired depth underwater, and calibrate other sensors when their response changes with pressure [3]. For this, a reliable, robust, flexible, lightweight, and surface-mountable sensing systems is needed to be deployed on AUVs to continuously monitor water pressure. This pressure measurements are also needed to understand the relation between the water level and other parameters such as pH, temperature and salinity etc. in water [4].