A Rapid Response/Recovery Ribbon‐like Hydroxyapatite Humidity Sensor with Loose Spatial Structure

Abstract

A rapid response/recovery ribbon‐like hydroxyapatite (HAp) humidity sensor with loose spatial structure has been fabricated in this work. The HAp film was prepared on polyethylene terephthalate‐indium tin oxide (PET‐ITO) interdigital substrate by electrochemical deposition method. The HAp film was characterized by XRD, SEM, FTIR techniques. Electrochemically deposited HAp has a preferred orientation in a‐plane, which exposes a great many of hydroxyl groups. The HAp has a flat ribbon‐like microstructure that effectively captures and detects water molecules. The gap of the interdigital electrode was filled with long ribbon‐like HAp to form a loose spatial structure which facilitates water molecules adsorption and desorption. The HAp humidity sensor showed high sensitivity, low hysteresis and good linearity. In particular, HAp sensor has a short response time of 0.9 s and recovery time of 5.6 s. Besides, the humidity sensing mechanism of HAp sensor was also investigated in detail.