Tactile-Sensing Based on Flexible PVDF Nanofibers via Electrospinning: A Review

Abstract

The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical performance have been widely utilized as functional materials in flexible tactile sensors. Polymer nanomaterials, representing the most promising materials, especially polyvinylidene fluoride (PVDF), PVDF co-polymer and their nanocomposites with ultra-sensitivity, high deformability, outstanding chemical resistance, high thermal stability and low permittivity, can meet the flexibility requirements for dynamic tactile sensing in wearable electronics. Electrospinning has been recognized as an excellent straightforward and versatile technique for preparing nanofiber materials. This review will present a brief overview of the recent advances in PVDF nanofibers by electrospinning for flexible tactile sensor applications. PVDF, PVDF co-polymers and their nanocomposites have been successfully formed as ultrafine nanofibers, even as randomly oriented PVDF nanofibers by electrospinning. These nanofibers used as the functional layers in flexible tactile sensors have been reviewed briefly in this paper. The β-phase content, which is the strongest polar moment contributing to piezoelectric properties among all the crystalline phases of PVDF, can be improved by adjusting the technical parameters in electrospun PVDF process. The piezoelectric properties and the sensibility for the pressure sensor are improved greatly when the PVDF fibers become more oriented. The tactile performance of PVDF composite nanofibers can be further promoted by doping with nanofillers and nanoclay. Electrospun P(VDF-TrFE) nanofiber mats used for the 3D pressure sensor achieved excellent sensitivity, even at 0.1 Pa. The most significant enhancement is that the aligned electrospun core-shell P(VDF-TrFE) nanofibers exhibited almost 40 times higher sensitivity than that of pressure sensor based on thin-film PVDF.

A Review of Piezoelectric PVDF Film by Electrospinning and Its Applications

“…Therefore, to further improve the piezo response in polymer materials, various nanofillers (graphene (Gr), carbon nanotubes (CNTs), nanofibers, etc.) have been synthesized and studied to fabricate polymer films [ 13 ].…”

Hydrothermally Grown ZnO Nanorods as Promising Materials for Low Cost Electronic Skin

“…All the above mentioned terminology for defining figures of merit for piezoelectric materials is perfectly fitting with PZT‐based elements, but it does not suit other types of piezoelectric materials in a straightforward manner. For example, piezoelectric elements based on PVDF, a polymeric material, have both electrical anisotropy of the vertical axis with respect to the other two (it is also a material that undergoes the poling treatment), and an intrinsic spatial anisotropy, due to the alignment of the polymeric chains along the poling direction. In this case the use of the same type of piezoelectric coefficients used for PZTs‐based elements can be misleading in terms of comparison between the two types of material.…”

Validation of Screen-Printed Electronic Skin Based on Piezoelectric Polymer Sensors

“…Its copolymer, Poly (vinylidene fluoride trifluoroethylene) or P(VDF-TrFE), is a ferroelectric material that does not need to undergo the mechanical stretching of the molecular chains along one of the transversal axes, leading to easier fabrication. Different fabrication technologies have been reported for P(VDF-TrFE)-based sensors, such as spin coating, electrospinning, sol-gel, chemical vapor deposition, micromachined mold transfer and inkjet printing [14]. The frequently used techniques, such as spin coating and inkjet printing, have limitations of process speed and overlay registration accuracy in multilayered structures.…”