## 3 Results and Discussion
### Requirements Evaluation
#### 3.3.5 Materials  
Carbon fiber was selected as the structural material in order to reduce weight while maintaining high mechanical resistance. The composite material presented in Figure 11a was constituted by System 2000 Fibreglast epoxy resin and carbon fiber 3K, 2 \(\times\) 2 will weave. All carbon fiber was covered with the polyester resin Duratec, which provides UV protection and high-gloss cosmetics properties. This commercial resin was enriched with titanium dioxide nanoparticles (TiO\({}_{2}\)) in order to achieve hydrophobic properties. The contact angle was measured with OCA 15 PLUS Datapysis equipment. The rectangular substrates of the treated carbon fiber, with a typical size of 1 \(\times\) 0.5\", were homogeneously covered with water droplets, which were stable and kept their spherical shape (Figure 11b,c). According to the measurements, the average contact angle was equal to 116\({}^{\circ}\)\(\pm\) 2\({}^{\circ}\) and the maximum contact angle was 128\({}^{\circ}\)\(\pm\) 3\({}^{\circ}\), matching the water repellence standard established for the material studied [33]. The average surface tension was equal to 72.7 \(\times\) 0.1 mN/m. Figure 11d,e shows AFM images of the substrate presenting a marked relief on a sub-micron scale, with an RMS roughness of 299.8 nm and an average roughness of 245.2 nm. These surface characteristics agree with the obtained hydrophobic properties of the material.  
Silicone is a widely used material for the handling of food products because it is totally inert and resists extreme temperatures. In addition, its non-slip properties caused by a high coefficient of friction provides an excellent grip. Therefore, silicone was selected as the material for the inner surfaces (Figure 12a), since this area of the Carbon HK VO hook is in contact with different objects, including food products. At this stage, a lab-scale prototype, Dragon Skin 30 silicone rubber, was used. This commercial silicone was enriched with silver nanoparticles (nSi@AgNPs) in order to achieve antibacterial properties. Figure 12b-e shows the pathway followed in the design of the antibacterial silicon grip. The process begins with the synthesis of nSi@AgNPs (powder), which is then incorporated into the silicone matrix (uncured silicone) to obtain a cured antibacterial silicone in the labsite and the final antibacterial silicone grip prototype. The AFM images presented in Figure 12f,g show a homogeneous dispersion of nSi@AgNPs on the silicone surface, as well as a mean roughness in the nanometric scale. In this way, our antibacterial silicone helps to keep the  
Figure 11: Surface properties of chemically treated carbon fiber: (**a**) carbon fiber material (blue) covered with hydrophobic polyester resin; (**b**) water repellence observed by depositing droplets on the surface; (**c**) characteristic image of a droplet with contact angles marked; (**d,e**) AFM images (2D and 3D representations, respectively) of the treated carbon fiber, showing details of surface relief and roughness.  
silicone grip free of bacteria, according to the antibacterial activity tested against _E. coli_ and _S. aureus_ as Gram-negative and Gram-positive bacteria models, respectively.