## 4 Conclusions  
In this study, thin-film batteries were pasted in the middle and corner of square PVC membranes. The saddle-shaped tension membrane structure was formed by applying pre-tension force along the direction of the membrane fiber and at the angle of 45 degrees between the fibers. The relationship between the voltage of the thin-film battery and the load was obtained. The conclusions are as follows:  
1. For PVC membranes under uniaxial tension, the membranes' principal strain increases with the increase of load. The tensile strength along the fiber angle of 45 degrees was 0.55 times that along the fiber direction. 2. For a two-way saddle-shaped tension membrane structure, the principal strain of thin-film batteries and PVC membranes at the exact location increases with the increase of load, and the strain of the former is always smaller than that of the latter. The strain cloud shows an uneven distribution, and the strain at the edge of the PVC film at the battery position was significant. 3. For a two-way saddle-shaped membrane structure, with the increase of tension load, the membrane battery expands gradually, and the principal strain increases gradually. However, the output voltage decreases gradually, and the voltage of the battery at the center of the membrane structure decreases 1.5-2.1 times as much as that at the corner. Thin-film batteries located at the center of the membrane structure are more affected by load than those located at corners. Due to the ropes' influence around the membrane structure, two-way tensioned membrane material properties are different from those of uniaxial tension. When the direction of the membrane fibers and the cable were perpendicular to each other, a more significant ultimate load was provided. 4. When the thin-film battery voltage decreases by 10%, the load level corresponding to different tension modes can be up to 100% and down to 25%. In order to ensure that the thin-film battery's voltage position is above 90% of the initial voltage, it is recommended that the principal longitudinal strain of the thin-film battery be less than 2.8% and that of the PVC film at the thin-film battery position be less than 3.1%. It is suggested that the position of the membrane battery, the direction of tension, and the direction of the membrane fibers should be taken as bases for applying the tension load values. Conceptualization, J.Y. ; Data curation, S.Q. ; Formal analysis, J.Y. ; Funding acquisition, J.Y. and Y.H. ; Methodology, J.Y. and J.H. ; Project administration, J.Y. ; Software, J.H. and S.Q. ; Supervision, J.Y. and Y.H. ; Writing--original draft, S.Q. ; Writing--review & editing, J.Y. Study design and organisation, J.Y. and Y.H. ; Experiments, analyzed the data and wrote the manuscript of this paper, J.H. and S.Q. Review the paper and confirm the results, J.Y. and Y.H. All authors have read and agreed to the published version of the manuscript. \begin{table}
\begin{tabular}{c c c c c} \hline
**Battery** & **Load Level** & **Strain of Battery/\%** & **The Strain of Membrane Material/\%** & **Expansion Area Ratio** \\ \hline A & 1 & 3.89 & 8.35 & 1.04 \\ B & 0.67 & 2.89 & 3.66 & 1.04 \\ C & 0.92 & 4.34 & 16.53 & 1.05 \\ D & 0.25 & 2.86 & 3.19 & 1.03 \\ \hline \end{tabular}
\end{table} 
Table 2: Parameters when voltage drops to 90%. **Funding:** The authors acknowledge the financial support received from the National Natural Science Foundation of China (Grant No. 51768005), Natural Science Foundation of Guangxi (Grant No. 2018 GXNSFAA281333), Systematic Project of Guangxi Key Laboratory of Disaster Prevention and Structural Safety (2019 ZDK035). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Informed consent was obtained from all individual participants included in the study. **Data Availability Statement:** If necessary, the data covered in this article are available from the corresponding author. **Acknowledgments:** This research is sponsored by the National Natural Science Foundation of China (Grant No.