Unique Activity-Meter with Piezoelectric Poly(vinylidene difluoride) Films and Self Weight of the Sensor Nodes

Abstract

We have developed piezoelectric switches for application in ultra low-power wireless sensor nodes to monitor the health condition of chickens. Using Pb(Zr0.52,Ti0.48)O3 (PZT) thin films, we have developed S-shaped PZT cantilevers with proof masses. Since the resonant frequency of PZT devices is approximately 24 Hz, we have utilized their superharmonic resonance to detect chicken movements with frequencies as low as 5–15 Hz. By attaching sensor nodes to chickens, we successfully measured the activity of chickens. However, the PZT devices of other sensor nodes broke down. S-shaped PZT devices are adequate for low vibrations, but are beset by the structural problems of fragmentation upon impact. To address these problems, we examine a method of utilizing poly(vinylidene difluoride) (PVDF) films, which are tough and generate high piezoelectric output voltages under a large stress, as piezoelectric switches. We suggest that the self-weight of sensor nodes be used as the mass of the cantilevers of the PVDF films. One end of a PVDF film is fixed to the case of a sensor node, and the other end is attached to the sensor node. Since PVDF films are subjected to force generated by the self-weight of sensor nodes, high output voltages are expected. A result of measuring output voltages, we confirm the output voltages to be approximately the same as those of PZT devices below 15 Hz at 0.5 m/s2 vibration, which is close to chicken movements. Thus, we consider that we have successfully fabricated a tough wireless sensor node for chickens, utilizing the features of PVDF films.

Development of Flexible Piezoelectric Strain Sensor Array

“…Note that, in recent years, in the field of piezoelectric devices using flexible substrates, many structures using piezoelectric polymer materials having high flexibility, such as polyvinylidene difluoride (PVDF), have been reported . However, in this study, it was necessary to fabricate a transfer structure making full use of the MEMS process.…”

Smart Table Tennis Racket Using a Rubber Mounted Ultrathin Piezoelectric Sensor Array

“…Note that the ferroelectric polymer poly(vinylidene difluoride) (PVDF) has been used on flexible devices in many cases because of its high flexibility. (8)(9)(10) However, we used PZT because it is a proven ferroelectric material for microfabrication and the MEMS process. (11,12) Then, we patterned and etched the device layer with the piezoelectric structure slightly supported on the handle layer by reactive ion etching of the device, box, and handle layers.…”

Ultra-Thin Piezoelectric Strain Sensor Array Integrated on a Flexible Printed Circuit Involving Transfer Printing Methods

“…The total thickness of the piezoelectric structure was approximately 5.1 µm. Note that ferroelectric polymer poly(vinylidene difluoride) (PVDF) has been used on a flexible device in many cases because of its high flexibility [26][27][28]. However, we used PZT because it is a proven ferroelectric material for microfabrication and the MEMS process [29,30].…”