Waterproof airflow sensor for seabird bio-logging using a highly sensitive differential pressure sensor and nano-hole array

This paper presents an airflow sensor for seabird bio-logging. Although bio-logging methods have attracted attention in the evaluation of seabird flight performance, the airflow velocity has not been directly measured. Here, an airflow sensor is added to the bio-logging system, and a direct airflow velocity measurement is applied, thus enabling more accurate evaluation of the flight performance. To attach the sensor to the bio-logging system, the sensor must be waterproof because seabirds dive into the sea to prey on fish. In addition, the sensor must also be compact and have high sensitivity. Here, we propose a Pitot tube-type airflow sensor that satisfies these requirements. The proposed sensor is composed of microelectromechanical systems (MEMS) piezoresistive cantilevers as sensing elements with high sensitivity and anodic alumina membranes with a nano-hole array as the waterproof elements with airflow penetration. The developed sensor responded sufficiently to airflow velocities from 2 m/s to 20 m/s. In addition, the sensor maintained its sensitivity after plunging into the water and returning to the air. Therefore, the proposed sensor can be utilized for practical seabird bio-logging.