## 4 Conclusions  
As TiO\({}_{2}\) increases, the area surrounded by the \(I\)-\(V\) curve becomes small and MCF rubber DSSCs serve almost as photodiodes. Electrical resistance depends on the amount of TiO\({}_{2}\). As TiO\({}_{2}\) increases, the electrical resistance as piezo-resistivity at the initial zero pressure decreases; however, the electrical resistance under the greatest pressure increases and, therefore, the difference decreases.  
Built-in voltage and current under increasing compression and tension tend to first increase, then decrease, and then remain steady. The increase occurs under the smallest amount of compression or tension and, in the case of tension, occurs in the linear elastic region. Photo voltage and current under increasing tension show the same tendency as above; however, under increasing compression, they do not show the initial increase in values. In contrast, regardless of condition, electrical resistance tends to first increase, then decrease, and then remain constant. Regarding compression, increasing TiO\({}_{2}\) reduces the changes in built-in current and photocurrent, while, in the case of tension, increasing TiO\({}_{2}\) increases the change in built-in current but reduces the change in photocurrent.  
The particles and molecules in MCF rubber DSSCs are ionized, corresponding to \(A^{-}\) and \(D^{+}\). In addition, the present experimental results regarding the effect of TiO\({}_{2}\) on photovoltaics can be explained by the chemical-photovoltaic mechanism involving the behavior of dye, electrolyte solution, water, and rubber molecules and the catalytic effect of Ni and Fe\({}_{3}\)O\({}_{4}\) on the MCF,  
Figure 17: Effects of tension on the electric current as photo electricity: (**a**) at 2 g of TiO\({}_{2}\); (**b**) at 4 g of TiO\({}_{2}\); (**c**) at 5 g of TiO\({}_{2}\).  
TiO\({}_{2}\), and K, together with the Honda-Fuijishima effect. To summarize the chemical reactions in the case of light scattering, the creation of the photocurrent comes about by generating electrons; the chemical-photovoltaic mechanism is irrelevant to the behavior of rubber molecules where the operations of electrons are facilitated by the catalyst of TiO\({}_{2}\), Ni, and Fe\({}_{3}\)O\({}_{4}\).  
Because ordinary solar cells do not have the properties of large tension or compression, they are rigid and not very flexible, and solar cells having these properties are currently novel enough to be almost unknown. However, MCF rubber DSSCs typically have large tension and compression, and their production opens the door to a number of practical devices and instruments. MCF rubber solar cells are suitable for a great variety of engineering applications. Once they are ready to go into production, the present experimental results and the model of the chemical-photovoltaic mechanism will be of great interest. For further development of the MCF rubber DSSCs, large stretchable transparent glass needs to be developed because large stretchable MCF rubber DSSCs integrated with stretchable transparent glass bring about more practical and convenient devices and instruments. The study to develop the large stretchable transparent glass will be addressed in another investigation.  
For this research article, K.S. conceptualized the idea, designed and performed the experiments, analyzed the data, and wrote the paper; H.K., R.I., and H.T. contributed reagents/materials/analysis tools and analyzed the data. All authors have read and agreed to the published version of the manuscript.  
This work was supported in parts by JSPS KAKENHI Grant Number JP 18K04040 and by the Fukushima Innovation Coast Framework project \"Namie Town Creation with Revitalizics using Risk Communication Engineering: for Realization of Innovation Coast Framework\" in Japan.  
The funding sponsors had no role in the design of the study. The authors declare no conflict of interest.