| Codded variables | Input parameters | Levels | ||
| −1 | 0 | 1 | ||
| X1 | Applied voltage (kV) | 10 | 12.5 | 15 |
| X2 | Flow rate (mL/h) | 0.25 | 0.5 | 0.75 |
| X3 | Chitosan (%) | 20 | 30 | 40 |
| X4 | Tip to needle distance (cm) | 10 | 12.5 | 15 |