We have fabricated a fuel cell based on the tissue-derived biomaterial "chitin", and investigated its proton conductivity. It was found that chitin becomes the electrolyte of the fuel cell in the humidified condition, and power density of the fuel cell using chitin electrolyte becomes typically 1.35 mW/cm 2 at the 100% relative humidity. This result is the first result showing that the polysaccharide obtained from nature becomes the fuel cell electrolyte. Moreover, this result indicates that chitin is proton conductor in the humidified condition. In the chitin sheet plane, proton conductivity in chitin is observed approximately 0.1 S/m. Further, it was also found that chitin has the anisotropic proton conductivity. The proton conductivity along the chitin fiber direction is higher than that perpendicular to the chitin fiber direction. From these results, it is deduced that the formation of water bridges accompanied by hydration plays an important role in the appearance of proton conductivity in chitin.

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We have fabricated the fuel cell based on the tissue derived biomaterial "collagen" and investigated its proton transfer. It was found that "collagen" becomes the electrolyte of fuel cell in the humidified condition. The power density of the fuel cell becomes typically 8.6 W/m 2 in the 80% humidity. Further, these results indicate that collagen exhibits proton conductivity in the humidified condition. Both of proton conductivity and dielectric constant increase by the increase of humidity. From the analyses of the frequency dependence of AC conductivity, it was found that proton conductivity and the dielectric dispersion observed in the humidified condition are caused by the formation of the water bridge, which is bonded with the collagen peptide chain. Considering that hydration induces the formation of the water bridge and that increases proton conductivity and dielectric constant, it is deduced that proton transfer in the fuel cell based on collagen is caused by the breaking and rearrangement of hydrogen bond in the water bridge.

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