PVDF‐Based Flexible Piezoelectric Tactile Sensors: Review

Abstract

With the advent of the intelligence era, flexible piezoelectric tactile sensors are the key components for sensing information and sending signals. The performance parameters of piezoelectric sensors are closely related to the selection of piezoelectric materials. Compared with conventional piezoelectric materials, polyvinylidene fluoride (PVDF) has significant advantages in flexibility, stretchability, chemical stability, electromechanical conversion, ease of use, and acoustic propagation impedance. As a result, PVDF has become a popular topic of research. This paper introduces the working principle of piezoelectric materials and flexible piezoelectric sensors based on PVDF materials and details the research progress of different materials based on PVDF for the preparation of flexible piezoelectric tactile sensors, such as: PVDF and its copolymers for the preparation of flexible piezoelectric sensors and PVDF doped with other functional materials for the preparation of flexible piezoelectric sensors. In this paper, the advantages and disadvantages of different materials and the development prospects of PVDF flexible piezoelectric sensors are summarized to provide some insights for high‐performance flexible PVDF piezoelectric sensors.

Recent Advances in Tactile Sensory Systems: Mechanisms, Fabrication, and Applications

“…In the printing step, the inked stamp contacts the recipient substrate, and then the stamp is removed to release the devices onto the recipient substrate. The prerequisite for a successful pick-up step is that the adhesion strength at the stamp/device interface is greater than that at the device/donor interface, resulting in delamination at the device/donor interface and thereby transferring to the elastomer stamp [ 129 , 130 , 131 ]. For the printing step, the adhesion strength at the device/receiver interface is stronger than that at the stamp/device interface, thus enabling printing [ 132 , 133 , 134 ].…”

Flexible resistive tactile pressure sensors

“…Tactile sensors need to precisely perceive forces of various magnitudes and directions, generating electrical signals in real-time based on different operating principles to be transmitted to the system for analysis. Based on different ways of generating electrical signals, flexible tactile sensors can be classified into resistive, 13 capacitive, 14 inductive, 15 piezoelectric, 16 and triboelectric types. 17 Among them, researchers have focused extensively on flexible resistive tactile sensors due to their notable advantages, including high precision, sensitivity, a broad sensing range, uncomplicated structure, stability, reliability, ease of miniaturization, and robust overload capacity.…”

Disclosing Solid-Phase-Transition Mechanism from Nonpolar to Polar Poly(vinylidene fluoride) via In Situ Real-Space Visual Methods

“…The crystal structure of polymers is closely related to their properties and applications. The manipulation of polymorphic phases of polymers has consequently received widespread concerns. − Poly­(vinylidene fluoride) (PVDF) is a typical polymorphic semicrystalline polymer with at least three common crystal forms: α, β, and γ. − The α form is thermodynamically most stable and accessible. , It is, however, not wanted owing to its nonpolar nature. Therefore, either avoidance of its formation or conversion of it into the polar phase for piezo-, pyro-, or ferroelectric application has to be made. − Among the various polar phases, the β phase exhibits the highest polarization, resulting in excellent electrical properties. − Despite the superior polarization performance of the β phase, its practical application and development are often limited because of the harsh conditions required for its formation, including the use of nucleating agents, , high electric fields, , rapid quenching, or strong external force fields. , By contrast, the γ phase also displays higher polarity and can be obtained by a simple thermal treatment, such as direct crystallization from the melt at a high temperature, , or annealing the α phase at proper temperature through the solid phase transition. − Even though the γ crystals obtained via solid phase transition exhibit exactly the same crystal structure, they possess yet a much higher melting temperature (around 185–190 °C depending on the chemical structure) than those directly obtained from melt crystallization and thus been referred to as the γ′ phase. ,,− Notably, the Curie temperature of PVDF is expected to be higher than the melting temperature; thus, the polarity of the γ′ phase is expected to be kept above its melting temperature, which is significantly higher than that of the widely used piezoelectric poly­(vinylidene fluoride- co -trifluoroethylene) (P­(VDF-TrFE)) copolymers in the range of 55–128 °C. − Henc...…”

“…5−8 The α form is thermodynamically most stable and accessible. 1,9 It is, however, not wanted owing to its nonpolar nature. Therefore, either avoidance of its formation or conversion of it into the polar phase for piezo-, pyro-, or ferroelectric application has to be made.…”