## 4 Conclusions  
This paper proposes two small, low-cost, and highly sensitive microwave CSRR-based sensors for liquid characterization. The capillary glass test tube is filled with a water-ethanol mixture placed parallel to the sensor's ground surface in order to determine the dielectric parameters of different mixture concentrations. The CSRR-based bended sensor was designed by folding the flat sensor around an arbitrary cylinder. Very important results were obtained. The originality of the bended sensor offers the possibility of changing the test tube quickly and easily for multiple measurements. The diversity of the sensor's bended shape and the modification of the radius of the test tube significantly improve the sensitivity at different resonant frequencies (1.8 GHz, 1.9 GHz, 2 GHz, and 2.4 GHz). The proposed sensors have several advantages, such as small size, low cost, multi-performance ability, high sensitivity, and easy handling, making them ideal candidates for various applications.  
Conceptualization, S.M. ([PERSON]), C.Z. and D.S.; methodology, S.M. ([PERSON]), I.E. and M.P.; software, S.M. ([PERSON]), M.L.B., S.M. ([PERSON]) and R.Z.; validation, I.E., C.Z. and D.S.; formal analysis, S.M. ([PERSON]); investigation, M.P. and J.R.; writing--original draft preparation, S.M. ([PERSON]), C.Z. and D.S.; writing--review and editing, M.L.B., S.M. ([PERSON]) and I.E.; visualization, S.M. ([PERSON]); supervision, R.A.A.-A. and C.Z.; project administration, J.R. and I.E.; funding acquisition, J.R. and I.E. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Moore4 Medical project, funded within ECSEL JU in collaboration with the EU H2020 Framework Programme (H2020/2014-2020) under grant agreement H2020-ECSEL-2019-IA-876190, and the Fundacao para a Ciencia e Tecnologia (ECSEL/0006/2019). This project received funding in part from the DGRSDT (Direction Generale de la Recherche Scientifique et du Developpement Technologique), MESRS (Ministry of Higher Education and Scientific Research), Algeria.  
All data are included within the manuscript.  
This work was also supported by the General Directorate of Scientific Research and Technological Development (DGRSDT)-Ministry of Higher Education and Scientific Research (MESRS), Algeria, and funded by the FCT/MEC through national funds and, when applicable, co-financed by the ERDF, under the PT2020 Partnership Agreement under the UID/EEA/50008/2020 project.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Reference**} & **0\% Water** & **100\% Water** & & \\  & **Concentration** & **Concentration** & **\#f (MHz)** & **Maximum Q Factor** \\  & **Resonant Frequency** & **Resonant Frequency** & **(MHz)** & & \\ \hline
[18] & 3980 & 4250 & 270 & 7 \\
[20] & 1920 & 1530 & 390 & 9 \\
[32] & 2370 & 2020 & 350 & 32 \\
[34] & 1050 & 1500 & 450 & 5 \\
[35] & 265 & 210 & 55 & 8 \\
[37] & 1997 & 1962 & 35 & 42 \\
[41] & 2348 & 2302 & 46 & 47 \\
[46] & 1960 & 1855 & 105 & 26 \\
[47] & 3050 & 2990 & 60 & 55 \\ Proposed flat structure & 2418.5 & 2330.4 & 88.1 & 72.71 \\ Proposed bended structure & 1990.7 & 1596.3 & 394.5 & 27.9 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of the proposed sensor with data reported in the literature.