A Multifunctional Airflow Sensor Enabled by Optical Micro/nanofiber

Fiber-optic anemometers have attracted an increasing attention over the past decade owing to their high sensitivity, wide dynamic range, low power consumption, and immunity to electromagnetic interference. However, expensive instruments may limit their practical applications. Herein, a new type of airflow sensor based on optical micro/nanofiber (MNF) is proposed and realized. The sensing element is a flexible polydimethylsiloxane (PDMS) cantilever embedded with a U-shaped MNF. Upon exposure to airflow, the induced deflection of the cantilever results in a bending-dependent transmittance variation of the embedded MNF. The performance of the sensor can be engineered by tuning the cantilever thickness and/or the MNF diameter. When four cantilevers are arranged in two orthogonal directions, the transmittance of each cantilever will be dependent on both flow speed and direction. By analysing the output signals of the four cantilevers, omnidirectional airflow with flow speed within 15 m/s were experimentally measured. In addition, a variety of voice and respiratory signals can be monitored and distinguished in real-time using an optimized cantilever with a resolution of 0.012 m/s, presenting great potential for health monitoring applications.