## 3 Results and Discussion  
Electrospray parameters, e.g., concentration, the distance between nozzle and glass and the voltage were found to be fundamental factors for producing microparticles products as previously described [23]. Many parameters were studied to provide microparticles. One of the most vital factors was the type of solvent used [25]. The effects of the solvent type on the morphology of the PLA microparticles were studied using chloroform, DCM, ethanol and a mixture of these organic solvents [26]. In the process of standardization, firstly, chloroform was chosen as a solvent for dissolving PLA. According to the previously reported literature, the size and morphology of the microparticles have a strong correlation to the set distance between the nozzle and the glass slide [11]. The most obvious reason may be to keep the distance parameter. In this work, the experiment was started with 1 wt.% of PLA with a collection distance set at 12, 15 and 18 cm. Smaller and homogenous particles were produced from a 15 cm distance with an excellent morphology, and therefore, a 15 cm distance was kept fixed for all experiments conducted with varying concentrations. In addition to distance, morphology and homogeneity of the particle may directly be affected by the solvent concentration [27]. Table 1 shows the concentrations of PLA-chloroform solution, voltage and flow rate parameters that were used in our optimization experiments. The alteration of particle morphology was evaluated using an optical microscope by considering parameter changes. Then, the two best optical images were chosen to perform SEM experiments considering the monodispersed structure and morphology of particles. Both particles were selected according to the optical microscopy results that were sprayed on a 40 \(\mu\)L/min flow rate, and their concentrations are 2 wt.% and 4 wt.%, respectively. SEM micrographs of particles  
Figure 1: Electrospray set-up. that formed from 2 wt.% (Figure 2A) and 4 wt.% (Figure 2B) concentrated solutions are porous in nature and microscale in size. Figure 2: SEM micrographs of prepared microparticles. (**A**) 2 wt.% polylactic acid (PLA)–chloroform and (**B**) 4 wt.% PLA–chloroform solution. Furthermore, from Figure 2A, it can be observed that the diameter of the particles increased as the PLA concentration increased. [PERSON] et al. examined the effect of PLA prepared in different concentrations varying between 0.05% and 0.15% (\(w/v\)) in organic solvents on the size of microparticles. They found that the particle diameter increased with high polymer concentrations [28]. Aside from these, neither fibers nor beaded fibrous morphologies were observed in our samples. SEM images also indicated that the chain entanglement point for fiber production did not reach what was stated in our previous work [27]. Despite all the different parameters that were chosen in combination, the desired particle could not be reached. As a result, the optimization of microparticles using chloroform is challenging. Therefore, it was decided to use a different material for this solution. Secondly, ethanol was added to the PLA-chloroform solution as in the previous studies [24]. Since it was decided to use 15 cm for distance, the effects of all other parameters were investigated, except distance. All the samples were examined by optical microscopy, and the best ones were chosen for the SEM study. Therefore, SEM images were taken for the 3 wt.% PLA ethanol-chloroform solution with 12 and 15 \(\upmu\)L/min flow rates (Figure 3). As seen in Figure 3A, by increasing the voltage from 26 to 29 kV, the diameter of the particles was decreased from 3.14 \(\upmu\)m to 2.81 \(\upmu\)m with a 12 \(\upmu\)L/min flow rate. However, spherical morphology was found to be disrupted. Additionally, it was observed that beaded nanofibers were formed in higher voltage. Then, the effects of flow rate and voltage on particle morphology and sizes were investigated by keeping other parameters fixed (Figure 3B).