Introduction

Sensor materials are used to transform one form of energy into another form of energy and are widely used in sensing detection. The huge growth of microprocessor applications has driven the needs of sensors in a variety of applications. Today, in the $18 billion global sensor market, piezoelectric polymer sensors are among the fastest growing technologies. Like any other new technology, in many applications, the "piezoelectric film" has been considered as a solution for sensors. In the 20 years since the discovery of the piezoelectric polymer polymer (PZT), the technology has matured, and the practical application is emerging, and the process of commercialization of technology is accelerating.

This manual provides a summary of piezoelectric polymer technology, terminology, characteristics and sensor design considerations. It also explores many applications of sensors that have been successfully developed in recent years.

Solving the unique sensing problems is the unique strength of our application engineers. We are very pleased to have the opportunity to help you in your design when considering the application of the piezoelectric film sensor.

background

"Piezoelectricity", the Greek language called "pressure", was discovered by the Gurie brothers more than 100 years ago. They found that quartz changes its shape and size under the action of an electric field, and, on the contrary, produces electric charges when it is mechanically deformed. The first practical application of this technology was achieved by another French Langevin in 1920. He has developed a crystal transmitter and receiver for underwater sound, that is, the first sonar. Before the two World War, researchers found that some ceramics produce piezoelectric properties under the action of high polarization voltage, which is similar to the magnetization of ferromagnetic materials.

By 60s, researchers have found that there is a weak piezoelectric effect in the bones and tendons of whale. So it started a serious exploration of other organic materials that might have the effect of piezoelectricity. In 1969, Kawai found a high piezoelectricity in the polarized fluoropolymer and polyvinylidene fluoride (PVDF). Other materials, such as nylon and PVC, also show a piezoelectric effect, but none of them can be as high as the PVDF and its copolymers.

Like other ferroelectric materials, PVDF also has high thermoelectric properties, which can produce electric charges in response to temperature changes. PVDF has a strong absorbability for the infrared energy of the wavelength of 7~20 m (see Figure 1), covering the same wavelength spectrum of the human body heat. Therefore, PVDF can be used as a very useful human motion sensor and thermoelectric sensor for more complex applications, such as night vision vidicon camera and laser beam imaging sensor. The piezoelectric thin film is suitable for the Finel lens

To detect the movement of human body 50 feet away and has been applied to the infrared detector of a satellite.

The new PVDF copolymer has been developed in the last two years, which has further expanded the application of piezoelectric polymer sensors. The copolymers can be used at a higher temperature (135 degrees C) and also provide the desired new shapes: cylindrical and hemispherical shapes. The thickness limit also reached the extent that the PVDF could not be achieved. These achievements include ultra-thin (200A) centrifugally cast cladding, which opens up the possibility of new silicon based sensor applications and wall thickness sensors for cylindrical sonar exceeding 1200 m.