To inhibit damage of electro-osmosis material even when impact is caused.

A circular opening 61 is formed in the center part of a support frame 6, and electro-osmosis materials 3 are arranged and supported in the opening 61. Damping chambers (spaces) 62 are formed on the support frame 6 in the circumference of the opening 61. Elastic strips 63 separating the damping chambers 62 and the opening 61 are formed because the damping chambers 62 are penetrated, and projections 64 arranged in the center part in the circumferential direction of the elastic strips 63 protrude toward the center of the opening 61. The electro-osmosis materials 3 are fit inside the opening 61, the edges of the electro-osmosis materials 3 abut to the projections 64, and the electro-osmosis materials 3 are supported by the projections 64 and the elastic strips 63. Damping materials 65 are filled in the gaps between the edges of the electro-osmosis materials 3 and the wall part of the opening 61.