## Effect of TiO\({}_{2}\) on Photovoltaics  
### Experimental Procedure  
The experimental procedure of fabricating the MCF rubber DSSCs is shown in Figure 12 in Appendix A. As the first step, we fabricated the MCF rubber. The MCF rubber included the n-type semiconductor TiO\({}_{2}\) (titanium with a 10-50 nm particle size, anatase form, Fujifilm Wako Pure ChemicalCo., Ltd., Osaka, Japan), 6 g of carbonyl Ni powder with \(\upmu\)m ordered and pimple-shaped particles (No. 123, Yamaishi Co., Ltd., Noda, Japan), 4.5 g of water-based magnetic fluid (MF) with 40 wt.% Fe\({}_{3}\)O\({}_{4}\) (W-40 with 10 nm ordered sphere particles, Ichinen Chemicals Co., Ltd., Shibaura, Japan), and 9 g of NR latex (Rejitex Co., Ltd., Atsugi, Japan), mixed using a supersonic stirrer (UR-20P, Tomy Seiko Co., Ltd., Tokyo, Japan) for 5 min and with air evacuated for 15 min. During electrolytic polymerization, an electric field with constant 6 V and 2.7 A was applied between stainless-steel plates with a 1 mm gap for 10 min under atmospheric conditions under the application of a constant 188 mT magnetic field created by neodymium permanent magnets between the electrodes. Therefore, the directions of the electric and magnetic fields were the same. The electrolytically polymerized MCF rubbers had an area of almost 20 mm \(\times\) 23 mm and a thickness of 1 mm. Next, we constructed the MCF rubber DSSCs. First, 0.17 g of electrolytes and 0.06 g of liquid dye were poured onto the surface of the MCF rubber. The electrolytes took the form of a KI + I\({}_{2}\) solution, a mixture of potassium iodide (KI) and iodine (I\({}_{2}\)) (both from Fujifilm Wako). KI contains 3.3 g of iodine I\({}_{2}\) in a solution of 40 g of potassium iodide KI and 60 g of water. The dye is based on ruthenium complexes PEC-TOM-P04 (Peccell Technologies Co., Ltd., Yokohama, Japan). The use of ruthenium dye is ordinary in DSSCs [48]. As shown in Figure A1 (Appendix A), the electrolyte solution was deposited on one side of the MCF rubber at the cathode during electrolytic polymerization (a in Figure A1, Appendix A), and the dye on the other side was deposited at the anode (b in Figure A1, Appendix A). The surface of side a in Figure A1 (Appendix A) was in contact with a transparent glass to serve as an anode of the solar cells, and the surface of side b in Figure A1 (Appendix A) was in contact with a transparent glass coated with TiO\({}_{2}\) as a cathode of the solar cell; the MCF rubber was sandwiched between the transparent glasses (20 mm \(\times\) 30 mm), as shown in Figure 1. The transparent electrode coated with TiO\({}_{2}\) was illuminated by visible light (238 Lux) or ultraviolet light (227 Lux). The voltage, electric current, and electrical resistance between the electrodes were measured using a digital multimeter (PC710, Sanwa Supply Co., Ltd., Okayama, Japan).  
The surface of the electrolytically polymerized MCF rubber is shown in Figure 2. The cathode side (Figure 2b,d) is typical and shows that the more TiO\({}_{2}\) the MCF rubber has, the harder it is to compound TiO\({}_{2}\). The compound condition of TiO\({}_{2}\) affects the photovoltaics, as shown in the later figures in the next section.  
Figure 1: Images of fabricated magnetic compound fluid (MCF) rubber dye-sensitized solar cells (DSSCs): (**a**) transparent glass on the anode size of the DSSC; (**b**) glass on the cathode side of the DSSC, coated with TiO\({}_{2}\).  
The MCF rubber involving TiO\({}_{2}\) has larger stretchability than commercial pressure-sensitive electrically conductive rubber (PSECR), as shown in our previous study [31]. DSSCs made of MCF rubber involving TiO\({}_{2}\) are the most desirable as soft materials in robots or flexible devices, enough to be wearable and portable.