Electrohydrodynamic jet printed bioinspired piezoelectric hair-like sensor for high-sensitivity air-flow detection

Inspired by the highly sensitive hairs of creatures in nature, this work proposes a high-aspect-ratio piezoelectric sensor that is processed using electrohydrodynamic jet (E-jet) printing technology. A thin layer of piezoelectric material is directly written on the surface of tungsten steel microwire by E-jet printing. The piezoelectric material was crystallized by high-temperature annealing and fully bonded to the microwire. The annealed piezoelectric thin film was then sputtered with copper electrodes which forms a piezoelectric hair-like sensor with a diameter of 120 μm and an aspect ratio of 300. It was observed that the piezoelectric hair-like sensor generates 18 mV with a displacement of 100 μm. The output signal increases linearly with the increase of lateral displacement and velocity. It was examined that the piezoelectric hair-like sensor can detect airflow velocity as low as 0.01 m s⁻¹, which shows a lower detection threshold compared to piezoelectric hair-like airflow sensors processed in other ways. In addition, the piezoelectric hair-like sensor allows for the detection of an airflow velocity of 10 m s⁻¹ and a response time of 70 ms. The experimental results show that the piezoelectric hair-like sensor has high sensitivity, a wide detection range and rapid detection response, which is expected to be a high-performance sensor for biosensing and airflow monitoring.