Design and fabrication of flexible piezoelectric materials and devices

Abstract

Ferroelectric materials can be widely used in many applications, such as transducers, actuators, self-powered sensors, energy harvesters, and FRAM. In the past, most devices have been based on piezoelectric ceramics. Although these materials have shown great performance, they are quite brittle and have difficulty in device integration.

Recently, wearable and implantable technologies have received increasing interest as a result of the growing demands for human interactive applications. Flexibility is one of the key considerations in these applications because the devices are in contact with the surface of the human skin and organs as well as, curved objects. If the devices have high flexibility, they can be used for a wider range of applications. In this study, we designed and fabricated flexible devices based on piezoelectric materials that, can be attached to the curved surface.

Chapter 1. We report a PVDF-based liquid volume sensor. When a liquid container vibrates due to an applied impact, our sensor that is attached to the surface of the container detects the resonance frequency of vibration, which shifts as a result of change in the liquid volume.

Chapter 2. We report a multifunctional stretchable piezoelectric fiber. The fiber is light weight, flexible, and twistable. Further, the fiber can be stretched to 100% without breakage. During finger tapping or stretching process, the fiber exhibited output voltages of 1.2 or 0.8 V, respectively. The fiber was confirmed to harvest mechanical energy from liquid pressure fluctuations.

Chapter 3. We report a porous composite-based pressure sensor for cochlear implant. We demonstrated that the output signals of the porous structure composite were much higher than those of a flat composite when sound was applied. In addition, the compressive modulus of the composite decreased to one tenth when pores formed.