## 3 Results and Discussion
### Facemask Prototype: Assembling of the Different Layers and Their Evaluation  
After selecting the best electrospun membrane to act as a filter and antibacterial layer, the assembling of the different facemask's layers was performed. Since this work aims for the development of an eco-friendly facemask, the chosen material for the inner and outer layers of the mask was a natural fabric (cotton). Three different configurations were evaluated, as exemplified in Figure 5: (i) inner and outer layers composed by cotton fabrics; (ii) inner and outer layers composed by cotton fabrics and a middle layer of PCL/MgO NPs electrospun membrane; (iii) inner and outer layers composed by cotton fabrics and two middle layers of PCL/MgO NPs electrospun membrane. Natural cellulosic fibers, such as cotton, present remarkable characteristics. Besides their natural origin, these fibers have good mechanical strength, high abundance, low cost, hydrophilicity, biocompatibility, nontoxicity, washability, reusability and provide breathability, being a suitable and sustainable option for facemasks. Moreover, cotton fabrics could be functionalized in order to achieve the required properties [3; 28]. For these reasons, the facemask prototype was developed using cotton fabric for the inner and outer layers. After the assembly of the different layers, filtration efficiency and air permeability tests were performed. The results are demonstrated in Table 4.  
As demonstrated by Table 4, the filtration efficiency of the cotton fabrics is low (15.6%), the main aim of these layers being to act as a support for PCL/NPs electrospun membranes and to not have a significant influence on the filtration performance. The addition of electrospun membranes in the middle of the two cotton layers significantly improved the filtration efficiency, confirming that these membranes are responsible for the filtration capacity, whereas they promoted a reduction in air permeability. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Samples**} & **Filtration Efficiency** & **Air Permeability** \\  & **(\%)** & **(L/min)** \\ \hline Cotton + Cotton & 15.6 & 28.5 \\ \hline Cotton + PCL/MgO NPs electrospun & & \\ membrane + Cotton & & \\ \hline Cotton + 2\(\times\) PCL/MgO NPs electrospun & & \\ membrane + Cotton & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Filtration efficiency (%) and air permeability (L/min) of the different facemask configurations evaluated (Cotton + Cotton, Cotton + PCL/MgO NPs electrospun membrane + Cotton + 2\(\times\) PCL/MgO NPs electrospun membrane + Cotton.). Figure 5: Schematic representation of the three configurations evaluated: (a) Cotton + Cotton; (b) Cotton + PCL/MgO NPs electrospun membrane + Cotton and (c) Cotton + 2 \(\times\) PCL/MgO NPs electrospun membrane + Cotton. The incorporation of two PCL/MgO NPs membranes as filter layers improved the filtration efficiency from 96.2 to 99.1%. Nevertheless, it decreased the air permeability of the facemask. These results were expected, since the incorporation of another filter layer composed of fibers with the same diameters and the same type and amount of NPs will promote an increase in thickness and basis weight, and consequently, a reduction in the air permeability. In fact, increasing the membranes' thickness provides more opportunities for the particles to meet with the fibers when they are traveling through the membrane [55]. [PERSON] et al. also showed that the percentage of porosity of the electrospun membranes is reduced when a higher basis weight is deposited, which can also contribute to a decrease in breathability [6]. Thermal Management Using Different Facemask Prototypes  
Wearing a facemask could result in higher face temperature, leading to overall discomfort while wearing them [56]. In order to evaluate this parameter, the facial temperature changes were recorded in three different locations (nose, mouth and cheek) using the three facemask configurations.