Emulsion Electrospinning of Polytetrafluoroethylene (PTFE) Nanofibrous Membranes for High-Performance Triboelectric Nanogenerators

Abstract

Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoroethylene/polyethene oxide (PTFE/PEO) membranes were fabricated, followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilized against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which was further corroborated by FTIR measurements. To enhance the ensuing triboelectric surface charge, a facile negative charge-injection process was carried out onto the electrospun (ES) PTFE subsequently. The fabricated TENG gave a stabilized peak-to-peak open-circuit voltage (V) of up to ∼900 V, a short-circuit current density (J) of ∼20 mA m, and a corresponding charge density of ∼149 μC m, which are ∼12, 14, and 11 times higher than the corresponding values prior to the ion-injection treatment. This increase in the surface charge density is caused by the inversion of positive surface charges with the simultaneous increase in the negative surface charge on the PTFE surface, which was confirmed by using EFM measurements. The negative charge injection led to an enhanced power output density of ∼9 W m with high stability as confirmed from the continuous operation of the ion-injected PTFE/PA6 TENG for 30 000 operation cycles, without any significant reduction in the output. The work thus introduces a relatively simple, cost-effective, and environmentally friendly technique for fabricating fibrous fluoropolymer polymer membranes with high thermal/chemical resistance in TENG field and a direct ion-injection method which is able to dramatically improve the surface negative charge density of the PTFE fibrous membranes.

Expanding the portfolio of tribo-positive materials: Aniline formaldehyde condensates for high charge density triboelectric nanogenerators

“…In the case of dielectric materials, these exchanged charges remain on the surface, leading to the formation of uncompensated dipoles, which can be extracted using the metal electrodes as the harvested charge [3]. Indeed, this phenomenon has been used to develop triboelectric nanogenerators (TENGs), which have been utilized to convert various forms of ambient mechanical energy to electrical energy [3][4][5][6][7][8]. The commonly reported vertical contact mode TENGs typically consist of a combination of dielectric/dielectric or dielectric/metal, with significant differences in their ability to donate (tribo-positive) or accept electrons (tribo-negative).…”

“…The commonly reported vertical contact mode TENGs typically consist of a combination of dielectric/dielectric or dielectric/metal, with significant differences in their ability to donate (tribo-positive) or accept electrons (tribo-negative). For these TENG systems, the increase in the output power and surface charge density is achieved via: (i) judicious selection of tribomaterials [8], (ii) surface micro-/nano-structuring [9,10], surface chemistry modification [11], (iii) charge injection [6] or composites with high-polarization piezoelectric additives [5,7,12] and (iv) physical hybridization of multiple energy harvesting technologies [13]. Except for the judicious use of tribo-materials, the rest of the methods are reliant on expensive equipment and complicated processing steps including lithography etc.…”

Comb-structured triboelectric nanogenerators for multi-directional energy scavenging from human movements

“…For the conventional TENGs, they have a maximum output power at a resistance between 1 and 100 MΩ because they have a high internal resistance in case of metalto-polymer and polymer-polymer contact. When we compare our system with previous studies, we believe that our resistance at the maximum output power is reasonable [9,[25][26][27][28].…”

Electrospun Polytetrafluoroethylene Nanofibrous Membrane for High-Performance Self-Powered Sensors

“…As shown in Fig. 1d, the pristine PEO exhibits several prominent peaks at 841, 947, 1059, 1092, and 1342 cm −1 , corresponding to the vibrations of the CH 2 and CO groups [22, 25]. On the other hand, there are five strong peaks showed up in the FTIR spectrum of the pristine PTFE, among which the most prominent ones at 1146 and 1201 cm −1 are characteristic of CF 2 symmetric and asymmetric stretching modes, respectively [26], and the peaks at 512, 554, and 639 cm −1 could be assigned to the rocking, deformation, and wagging modes of CF 2 , respectively [27].…”

“…It is well known that increasing the microscopic surface area of the triboelectric generator can enhance its effective surface charge density at the same time and therefore promotes its output performance as well [21]. Recently, using electrospun PTFE nanofibrous membrane as an alternative to commercial PTFE thin-film has been proved to be an effective method to promote the performance of triboelectric NG, because of the much larger surface area of the former [22]. The surface charge density is also the key factor that determines the performance of an electret, suggesting electrospun PTFE nanofibrous membrane may be used for the construction of high-performance electret devices.…”