Ion-beam irradiated layer is exfoliated from poly(lactic acid) (PLLA) substrate as a sheet when immersed in a buffer solution. By using this technique, cellular sheets are obtained without proteins degradation enzyme, which damaged proteins around cell to construct organs. However, the exfoliation mechanism is uncertain. In this study, the effects of irradiation condition and ambient condition on the fabrication of biodegradable sheets were studied.

To evaluate ion species effect, H⁺, H₂⁺, He⁺, N⁺, O⁺, Ne⁺, N₂⁺, O₂⁺, Ar⁺, and Kr⁺ were irradiated into PLLA sheets at an energy of 150 keV with a fluence of 1E15 ions/cm², respectively. He⁺ was irradiated at an energy of 150 keV with fluences between 5E14 to 3E15 ions/cm² in order to investigate fluence effect. By changing the media pH and environmental temperature, the relationship between ambient conditions and the exfoliation phenomenon was investigated.

H⁺, H₂⁺ or He⁺ irradiation is suitable for developing biodegradable sheets. He⁺-irradiated layer at high fluence was easily broken, which is highly carbonized. These results suggested that the thickness of the irradiated layer and the degree of carbonization were related to the fabrication of the thin films. The exfoliation time became shorter at high pH or high temperature. This behavior is comparable to the hydrolysis of PLLA.

The cellular sheets consist of biodegradable polymer and have good cell affinity, which is expected for application of scaffolds for tissue engineering, artificial organs, and cell diagnosis tools.