Airflow Sensor Using Standing Laser-Induced Graphene Cantilevers

Various animals in nature, particularly insects, possess sensory hairs that can detect minute fluid forces. Numerous airflow sensors, inspired by these insect sensory hairs, have been developed using silicon-based micro-electro-mechanical systems (MEMS) technology. However, the intricate fabrication process and the challenge of integrating shape-controlled sensing elements on the same substrate have posed significant obstacles. On the other hand, laser-induced graphene (LIG) has emerged as a promising material for various physical sensors due to its high sensitivity as a piezoresistive material and its simplicity of production. Polyimide (PI), the most commonly used material for LIG formation, is thermoplastic, enabling the creation of 3-D shapes with ease. In this study, we propose a single-axis airflow sensor with upright LIG cantilevers. The process involves the use of an ultraviolet (UV) laser to cut a PI substrate into cantilever shapes and a CO2 laser to form LIG sensing elements. Subsequently, thermal deformation is employed to bend the cantilevers at right angles. The resulting sensor measures
$25\times25$
mm at its base and stands at a height of 10.2 mm. Wind tunnel experiments validated the sensor’s performance, showing a quadratic increase in response with wind velocity ranging from 2 to 12 m/s, consistent with theoretical expectations. Furthermore, the baseline shift observed with repeated wind application was significantly small. This approach holds great promise for the development of airflow sensors inspired by sensory hairs of insects.