## 1 Introduction  
Ordinary solar cells are fabricated as a solid-state material and are typically used in the configuration state as a flat plate so that they are difficult to bend, compress by pressure, or expand by tension, and cannot withstand impact and load forces. However, if a solar cell could be made flexible, elastic and extensible, many engineering application concepts could benefit from this development to achieve marked progress. In robotics, for example, it could be used in human-like robots as an artificial skin. No power supply would be required to drive their motors and sensors, because electric power would be generated by the solar cells. In addition, the robot's skin would be able to move with a supple motion similar to that of humans. We can propose that rubber is one of elasticized materialsusable for realizing a flexible solar cell. Flexible solar power generators have been investigated recently [1; 2; 3; 4; 5; 6; 7], although they have remained within the realm of the solid state. This is due to the conducting polymer. Therefore, the effect of tension and compression on photovoltaics has not been investigated. Unfortunately, there have been only a few attempts at using rubber in this field. Investigations utilizing polysiloxane rubber [8] and styrene-butadiene-rubber [9] are the only noteworthy examples. However, these investigations did not clarify the effect of the properties of the rubber, including tension and compression, on the photovoltaics. Induced output, voltage and current were clarified, but the effects of tension and compression have not been elucidated. In the present study, we attempt the fabrication of a solar cell utilizing rubber and to investigate the effect of tension and compression on the photovoltaics. There are some useful principles to be gleaned from the fabrication process of ordinary solid-state solar cells for the present effort of constructing a flexible, elastic and extensible solar cell. They are primarily categorized in fields concerning the containing components: organic or inorganic material [6; 10; 11]; organic or inorganic material involving lipids [12]: ionic liquid [1; 13; 14; 15; 16; 17]: dielectric liquid [18], etc. Among them, the principles of the electrolyte system as a situated wet-type solar cell [19; 20] or dye-sensitized one [21; 22] such as a Gratzel-type solar cell [23], are particularly useful for the solar cell developed here, as the rubber described below is a water-soluble flux. In addition, low-cost and lightweight conditions are required in the engineering production of solar cells. In the first report [24], we investigated the possibility of a novel rubber-type solar cell with a sensing, magnetic compound fluid (MCF) rubber solar cell, which correspond to a new type of artificial skin named \"hybrid skin (H-Skin)\" with the hybrid functions of elasticity, flexibility, photovoltaics and piezoelectricity obtained by synthesis using natural rubber (NR)-latex, MCF, TiO\({}_{2}\) particles, dye and electrolyte, with reference to the principles of the fabrication of wet-type or dye-sensitized solar cells using a physical-chemical model. MCF is an intelligent fluid that is responsive to a magnetic field, first reported in 2001. It is a colloidal fluid involving 10-nm Fe\({}_{3}\)O\({}_{4}\) particles coated with oleic acid because of compounding magnetic fluid (MF), and other metal particles such as Fe, Ni or Cu on the order of 1 \(\upmu\)m [25]. When NR-latex is included in the MCF (called MCF rubber), it can be solidified under the application of a magnetic field, and magnetic clusters combined by the aggregation of Fe\({}_{3}\)O\({}_{4}\) and metal particles are formed along the direction of the magnetic field lines. We used a new method for solidification of water-soluble rubber, natural rubber (NR-latex) by electrolytic polymerization with a magnetic field; the electrolytic polymerization is a kind of electrolysis, and NR-latex is water-soluble and has C=C bonds.