Investigation of Slip Sensing Technology Based on the Conductive Sponge‐PVDF

Abstract

engineering applications, normal and shear force components are generated between the tactile sensor and the object when sensing the object's motion. [2] To extract the required data, the tactile sensor should have a good dynamic response to track oscillatory variations of normal and shear forces in real-time. Recently, sensors have been developed to detect the shear force. According to the detection principle, tactile sensors can be mainly divided into capacitive, [3][4][5] piezoresistive, [6,7] triboelectric, [8,9] and piezoelectric [10] sensors. In addition to the single sensing method, tactile sensors can also be combined with different sensing mechanisms. Accordingly, multimethod sensors such as piezoelectric-piezoresistive sensors [11] and capacitance-triboelectric sensors [12] have been proposed. Piezoresistive sensors, transduce pressure stimulate into electric signal. Considering the remarkable advantages of these sensors such as simple sensing mechanism, simple structure, and low power consumption, they have been widely used in diverse industries. [13] However, hysteresis, slip and force vectors are rarely reported and the root cause of hysteresis has not yet been investigated. Studies show that capacitive sensors have high strain sensitivity, and low power consumption, and are compatible with the static force measurement. [14] However, further investigations reveal that reducing the pixel size of these devices reduces the capacitance and the signal-to-noise ratio of the sensor. Considering the influence of fringe capacitance on the performance, these sensors are susceptible to external interference so their output characteristics are usually nonlinear. [15] Recently, self-powered triboelectric nanogenerators (TENGs) have been proposed as a promising technique with outstanding features and promising performance such as high flexibility, light weight, and high sensitivity even under mechanical stimuli of tiny amplitudes. Moreover, continuous friction may cause undesired wear and tear, thereby affecting the stability of the device during long-term operations. In the laboratory, the reproducibility and interchangeability of a single triboelectric device are limited by manual operations, which hinders largescale manufacturing and increases fabrication costs. [16] It is worth noting that although self-powered piezoelectric materials have superior characteristics such as high flexibility, light weight, and biocompatibility, they have relatively low energy conversion efficiency and sensitivity that should be improved. [17] In order to satisfy robotic requirements such as dexterous Tactile sensation is one of the most important senses in living things and smart devices to obtain the required data from the outside world, and slip is one of the main tactile information. In the present study, a slip sensor made of conductive sponge and polyvinylidene fluoride (PVDF) is proposed to sense the magnitude and direction of the sliding force. The structure and working principle of the sensor are analyzed using the finite...

PVDF‐Based Flexible Piezoelectric Tactile Sensors: Review

“…The primary goals of current piezoelectric tactile sensor research on PVDF-based materials are to increase PVDF's piezo-electric sensitivity and piezoelectric conversion efficiency. [55] On the one hand, the polarization of PVDF is accomplished by treatments such as stretching polarization, or by using processes such as electrostatic rotation during the application of high voltage. Mainly because the 𝛽-phase as the main piezoelectric phase, through processes such as stretching can transform the stable 𝛼phase into 𝛽-phase to improve its performance (see Section 2.3 for details of the transformation), and the high voltage applied during electrostatic spinning will align the dipoles in PVDF, and its mechanical strength can form a strong fiber network, effectively loading the polymer to form the 𝛽-phase, and during the application of pressure the structure is more stable and The piezoelectric properties are improved.…”

“…Currently, there are relatively few multifunctional tactile, tactile sensors that have been developed, most of which can only detect one quantity and have some shortcomings in performance. Wang [55] compared the performance of piezoelectric tactile sensors prepared by conductive sponge with RTV silicone rubber substrate and PDMS substrate as substrates, and the results showed that RTV silicone rubber and PDMS, as insulating materials, hindered the charge output of PVDF films. It is noteworthy that the porous mesh structure of the conductive sponge allows PVDF to produce higher piezoelectric output, but the detection amount is still relatively single and can only sense the magnitude direction of the slip force.…”

Threadlike Piezoelectric Sensors Based on Ferroelectrets and Their Application in Washable and Breathable Smart Clothing

“…Such nonlinearity in the figure may be caused by the enhancement of stiffness of the ferroelectret layer of the FCSs at high applied pressures which is often observed in ferroelectret films. [25] To improve the linearity of the FCSs, an extension of the elastic modulus range in the ferroelectret films is expected, which could be achieved by optimizing the mechanical cellular structure in the films. However, this topic is beyond the scope of this article and relevant work will be published in future papers.…”

“…1D threadlike electromechanical sensors include functional fibers [5,11,15,16] and piezoelectric wire/cable sensors. [17][18][19] The adopted mechanisms in them involve piezoresistance, [20,21] capacitance, [7,22,23] piezoelectricity, [24,25] and triboelectricity. [26] Regarding power consumption, the sensors based on triboelectric structures and piezoelectric materials are superior to the piezoresistance and capacitance-based sensors because no external power supply is needed.…”