## 3 Results and Discussion
### Functional Features, Limitations, and Directions of Potential Applications for the L-FDM Method
The aforementioned examples are just a glimpse of the vast application possibilities of the innovative L-FDM printing technique. Its potential and significant contributions to the field of science make it imperative to be explored and developed further. During the research, problems were encountered during the L-FDM printing process; it was also noticed that it has some limitations, but some of them can be overcome/circumvented by using solutions, examples of which are listed in Table 10. The first problem is the relatively small amount of modifier possible to be introduced into the polymer, and another problem is with the precise determination of its contents. The proposed solution to the above-mentioned problems is, for example, increasing the total surface of the polymer absorbing the modifier by reducing the diameter of the filament, increasing the porosity, or changing the material from which the filament is made. The amount of the introduced substance can be controlled by a quantitative analysis of the finished product or inline spectroscopic measurements performed during the printing process with the use of colored substances. Another challenge posed by L-FDM printing is the appropriate selection of solvents for the material from which the filament is made and the chemical substance from which we want to make the solution. If there is a problem with the dissolution of the polymer in an organic solvent, the solvent or polymer from which the filament is made should be changed. Another solution to the problem of dissolving the filament is to control the temperature of the solvent in such a way that only the introduced chemical substance is dissolved. During the L-FDM printing process, to maintain the homogeneity of the obtained 3D elements (uniform color or even introduction of the modifier into the polymer matrix), it is important to evenly cover the surface of the filament with the solution. For this purpose, in addition to the appropriate selection of the polymer and solvent, the addition of a surfactant can be used. Depending on the viscosity of the modifier solution, the filament is covered with a thicker or thinner layer after immersion. The filament is covered with a thicker layer of the modifier solution if it has a higher viscosity. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Feature** & **Limitations** & & **Solution** \\ \hline modifier content in the final product & & (a) & reducing the diameter of the filament \\   measurable value (\% \(w/w\)) & limited absorption & (b) & increasing the porosity of the \\  & & (c) & changing the composition of the filament \\ \hline  & difficulty with precise & (a) & quantitative analysis of the modifier in \\   precise dosing of the ingredient & determination of the amount of the modifier introduced & (b) & spectroscopic or optical \\  & & modifier introduced & measurement inline \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Features and limitations of the liquid for fused deposition modeling (L-FDM). The amount of absorbed solution from the reservoir by the polymer depends, among other factors, on the duration of its interaction with the filament. This time is influenced by the desired printing speed, which is the rate at which the material is fed.