Polyethylene (PE) and Ti surfaces were irradiated with oxygen cluster ions. For PE surfaces, the sputtered depth increased with an increase in acceleration voltage, and the sputtering yield was approximately 243 molecules per ion at an acceleration voltage of 9 kV. Atomic force microscopy showed that surface roughness increased with an increase in acceleration voltage. The contact angle was between 70° and 80°, which was smaller than that for the unirradiated surface. Adhesion of mesenchymal stem cells (MSCs) could be obtained by adjusting acceleration voltage, although cell adhesion was not observed on the unirradiated surfaces. For Ti surfaces, the surface roughness did not change with cluster ion irradiation. However, the contact angle decreased with an increase in acceleration voltage, and it was 46° at an acceleration voltage of 9 kV. Furthermore, after ultraviolet light irradiation for 30 min, the contact angle decreased to 28°. With regard to cell adhesion, the number of MSCs attached to the Ti surface increased after oxygen cluster ion irradiation.

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