# Graphene Deposition on Glass Fibers by Triboelectrification  
[PERSON]  
1 Department of Industrial Engineering, University of Trento, 38123 Trento, Italy; [EMAIL_ADDRESS] (L.S. ); [EMAIL_ADDRESS] (A.D.)1  
[PERSON]  
1 Department of Industrial Engineering, University of Trento, 38123 Trento, Italy; [EMAIL_ADDRESS] (L.S. ); [EMAIL_ADDRESS] (A.D.)1  
[PERSON]  
1 Department of Industrial Engineering, University of Trento, 38123 Trento, Italy; [EMAIL_ADDRESS] (L.S. ); [EMAIL_ADDRESS] (A.D.)12 National Inter  
Interphase tailoring by sizing or coating by nanofillers (like carbon nanotubes and graphene) on reinforcing fibers (glass or carbon) has been approached through various techniques, like spraying [3; 4; 5; 6; 7], solution coating [8; 9], dip coating [10; 11; 12; 13; 14; 15; 16], electrophoretic deposition (EPD) [17; 18; 19; 20; 21], and immersion [22; 23]. These methods allow the nanofillers to \"anchor\" on the fiber surface due to the chemical reactions between the functionalized nanofillers and the fiber's surface groups. In addition, it increases the local modulus of the interphase, along with its shear strength [2]. Moreover, such modifications may introduce multifunctional properties in the laminates, depending on the nanofiller type [24; 25; 26]. Most of the nanofiller deposition methods reported above require a tedious and energy-consuming setup. For example, in the case of spraying, special air brushes and high air pressures are required to deposit nanofillers with high dispersibility. It is reported that during this process, agglomeration of nanofiller in the air brush results in a non-uniform deposition of nanofiller on the substrate [3]. Moreover, EPD is based on a setup involving DC current source and particular electrodes to carry out the deposition [27]. The effectiveness of dip coating or immersion, on the other hand, depends either on the quality of the dispersion used to deposit the nanofiller and on the substrate's surface energy, since no energy is used to \"force\" the nanofiller towards the substrate. In very recent years, graphene has become a potential candidate for fiber coating since a limited filler content is required to provide excellent improvement of interlaminar properties [28]. This permits almost no degradation of the laminate's in-plane properties. Since its advent in 2004 [29], graphene has received unprecedented attention from the scientific community. Graphene, a single-layer carbon sheet with a hexagonal structure, possesses a remarkable array of properties, such as a high Young's modulus (\(\sim\)1 TPa) [30], large theoretical specific surface area (2630 m\({}^{2}\) g\({}^{-1}\)) [31], high carrier mobility at room temperature (\(\sim\)10,000 cm\({}^{2}\)/V\(\cdot\)s) [29], good optical transparency (\(\sim\)97.7%) [32] and excellent thermal conductivity (3000-5000 Wm\({}^{-1}\)K\({}^{-1}\)) [33]. Motivated by its unique and extraordinary properties, scientists around the world are constantly trying to exploit the full advantages of graphene in combination with various polymer matrices. However, the full technical exploitation of graphene in engineering applications is still a challenge. Interestingly, triboelectrification (TE), involving the generation of charges on the fiber surface, has never been investigated as a technique for fiber coating with nanofillers. TE is also known as contact electrification (CE), which technically means the creation of charges due to physical contact between (at least) two surfaces. Briefly, TE is a tribological process involving two dissimilar materials that, when come in contact or are rubbed with each other, creates an electrical charge on their surfaces. Under given contact conditions, the magnitude and type of charges depend on the specific triboelectrification behavior of the materials in contact. This is summarized in the form of the so-called triboelectric series, which rank different materials according to their \"tendency\" to gain or lose electrons during the process [34].