Fabrication of a polyvinylidene difluoride fiber with a metal core and its application as directional air flow sensor

Abstract

We fabricated a sensitive air flow detector that mimic the sensing mechanism found at the tail of some insects. [see Y. Yang, A. Klein, H. Bleckmann and C. Liu, Appl. Phys. Lett. 99(2) (2011); J. J. Heys, T. Gedeon, B. C. Knott and Y. Kim, J. Biomech. 41(5), 977 (2008); J. Tao and X. Yu, Smart Mat. Struct. 21(11) (2012)]. Our bionic airflow sensor uses a polyvinylidene difluoride (PVDF) microfiber with a molybdenum core which we produced with the hot extrusion tensile method. The surface of the fiber is partially coated with conductive silver adhesive that serve as surface electrodes. A third electrode, the metal core is used to polarize polyvinylidene difluoride (PVDF) under the surface electrodes. The cantilever beam structure of the prepared symmetric electrodes of metal core piezoelectric fiber (SMPF) is used as the artificial hair airflow sensor. The surface electrodes are used to measure output voltage. Our theoretical and experimental results show that the SMPF responds fast to air flow changes, the output charge has an exponential correlation with airflow velocity and a cosine relation with the direction of airflow. Our bionic airflow sensor with directional sensing ability can also measure air flow amplitude. [see H. Droogendijk, R. G. P. Sanders and G. J. M. Krijnen, New J. Phys. 15 (2013)]. By using two surface electrodes, our sensing circuit further improves sensitivity.

Bioinspired Fluffy Fabric with In Situ Grown Carbon Nanotubes for Ultrasensitive Wearable Airflow Sensor

“…However, the lowest detection limit was above 1 m s −1 . [8,23,25] In short, the CNTs/CSF airflow sensors show both of low detection limit and fast response, being superior than the previously reported airflow sensors (Table S1, Supporting Information).…”

“…Flexible airflow sensors are particularly useful in transmitting information according to Morse code by blowing the sensors, monitoring increasing and decreasing airflow velocity, and alerting blind people walking outside about potential hazard induced by nearby fast-moving objects.Traditional airflow sensors have been developed and used in weather monitoring, biomedical engineering, aerospace, and mineral enterprise. [17][18][19] The working mechanism of the reported airflow sensors includes measuring either the airflow-induced temperature variation [20][21][22] or the airflow-induced mechanical deformation which can be further characterized using piezoresistive, [8,[23][24][25] capacitive, optical, [16,26] or piezoelectric [27,28] approaches. However, those conventional airflow sensors are rigid, cumbersome, [20][21][22] and have high detection limits, [27,28] making them unsuitable for applications in wearable electronics.…”

“…Figure 3i compares the detection limit and response time of our airflow sensors with those of previously reported ones. [8,9,[15][16][17]22,23,25] Due to the fluff-like structure and the unique properties of CNTs/CSF, our sensor simultaneously achieves a low detection limit (0.05 m s −1 ) and fast response (1.3 s). In contrast, most of the airflow sensors reported so far cannot possess both low detection limit and fast response time, which limits their applications.…”

“…i) Detection limit and response time of our CNTs/CSF‐based airflow sensor in comparison with the reported airflow sensors in refs. .…”

Polymeric piezoelectric fiber with metal core produced by electrowetting‐aided dry spinning method

“…Tensile melt extruding is another effective way to generate metal-core PVDF and PVDF-TrFE fibers. 17,18 This method first places a metal filament in the center of melting PVDF or PVDF-TrFE, and then extrudes the polymer along with pulling the metal filament. Because the metal filament is kept in the center, PVDF or PVDF-TrFE fiber with metal core can be finally produced.…”