## 3 Results and Discussion
As a result, the voltage rate was determined to be 18 kVA. After all SEM images were acquired and the results were compared, it could be concluded that the formation of the microparticle is strongly dependent on the type of solvent used in the experiment. As shown in Figure 5A, the average diameter of the microparticles for 3 wt.% of PLA-DCM solution was obtained at \(\phi\) = 3.00 \(\pm\) 0.49 \(\upmu\)m. From Figure 5B, it is clearly observed that the average diameter of the microparticles of the 3 wt.% PLA--5 wt.% ethanol solution was found to be \(\phi\) = 3.01 \(\pm\) 0.58 \(\upmu\)m, and the microparticle radius for 2 wt.% PLA was obtained at \(\phi\) = 19.70 \(\pm\) 1.94 \(\upmu\)m (Figure 5C). In Figure 5C, the size and morphological properties of the microparticles were obtained as desired. According to these results, the diameter of the PLA-DCM microparticles was quite small and porous as desired. The surface tension played an important role at the interface  
Figure 4: SEM images and diameter distribution profile of 3%PLA—dichloromethane (DCM) solution. (**A**) Each line contains both a SEM image and diameter distribution graphic of 14, 16 and 18 kVA, respectively; the flow rate is fixed at 20 \(\upmu\)L/min. (**B**) SEM images and diameter distribution profile of 15 \(\upmu\)L/min at 18 kVA. of the viscous fluids for the formation of the spherical microparticles. It is known that DCM has higher surface tension compared to the other solvent used in this work, resulting in the formation of a better particle size and morphology. Further, DCM has a lower boiling point than that of chloroform and ethanol. [PERSON] et al. prepared PLA with DCM at very high concentrations of 10% to 20% (\(w/w\)) by adding various surfactants and obtained smooth, uniform microparticles [33]. The low boiling point of the solvent strongly controls the evaporation rate and the stability of particle formation during the electrospray process, which can further be easily controlled. Thus, the PLA-DCM solution has more suitable properties for the production of microparticles than the PLA-ethanol and PLA-chloroform solutions. In a previous study, undesirable structures such as cracked and irregular sunken surfaces were obtained in PLA microparticles produced with DCM solvent [23]. However, in this study, it was observed that PLA microparticles formed with DCM solvent have rough surfaces with highly porous or monodisperse structures. Therefore, using DCM as a solvent produced the best result among the solvents. The differences between the physical properties of the solvents, such as density, surface tension and viscosity, are seen in Table 2.  
Figure 5: (**A**) SEM images of the 3 wt.% PLA–DCM group sample. (**B**) SEM images and of the 3 wt.% PLA ethanol–chloroform group sample. (**C**) SEM images of the 2 wt.% PLA–chloroform group sample. The chemical configuration of pure PLA was confirmed through FTIR spectra scanned in the range of 4000 cm\({}^{-1}\)-500 cm\({}^{-1}\) (see Figure 6A,B). The characteristic absorption bands appeared for the C=O vibration band at 1749 cm\({}^{-1}\); the CH\({}_{3}\) asymmetrical scissoring band appeared at 1453 cm\({}^{-1}\); for C=O and C=O-C, the stretching band appeared at 1080 cm\({}^{-1}\); the C-CH\({}_{3}\) stretching band appeared at 1042 cm\({}^{-1}\); and for C-COO, the stretching band appeared at 867 cm\({}^{-1}\)[34; 35; 36]. Comparing the spectrum of pure PLA and the results for microparticles obtained after electrospray process, it was found that the spectra of pure PLA and the PLA microparticles obtained matched well to each other (Figure 6A). Further, these results matched well with the FTIR results reported for pure PLA in literature. Figure 6B shows the FTIR results of the PLA solutions in different solvents before the drying process. For chloroform, the characteristic absorption band appeared at 1214 cm\({}^{-1}\), which was assigned to CH-bending (\(\gamma\)4) modes [37]. The spectrum of PLA-ethanol-chloroform showed a negligible shift compared to the PLA-chloroform spectrum.