Spontaneous Wrinkle Formation on Polydimethylsiloxane Using Plasma Immersion Ion Implantation: Influence of Ion Species and Pulse Frequency

Plasma immersion ion implantation was carried out to create the wrinkle patterns on polydimethylsiloxane (PDMS). We demonstrated that the wrinkles were formed spontaneously without the application of the external agents and the wrinkle morphology as well as the geometry were dependent on the ion species and the high voltage pulse frequency. The PDMS was irradiated with hydrogen ions or argon ions in the plasma generated using radio frequency. The pulsed negative bias voltage was fixed at - 5 kV whereas the pulse frequency was varied to observe its influence on the wrinkles. Hydrogen irradiation resulted in the parallel patterns while random patterns were revealed after argon irradiation. The different wrinkle morphology could be attributed to the difference in energy loss processes of the ions; i.e., nuclear stopping and electronic stopping. The amplitude and wavelength of wrinkles increased almost linearly with the pulse frequency. This could be described in terms of the cross-linking and the thermal stress induced in the PDMS after irradiated with different pulse frequency. X-ray photoelectron spectroscopy analysis exhibited that ion irradiation transformed the surface of PDMS into silica-like with abundant oxygen functional groups that accommodated the formation of wrinkles in the PDMS. The polar component of surface energy of PDMS increased drastically after the irradiation due to the presence of oxygen functional groups, changing the PDMS surface to a more hydrophilic state. The polar component of surface energy scaled with the pulse frequency.

Automated summary

This study successfully created wrinkle patterns on PDMS using plasma immersion ion implantation. The results demonstrate that the wrinkles formed spontaneously without external agents, and their morphology and geometry were affected by the ion species and high voltage pulse frequency. X-ray photoelectron spectroscopy analysis revealed that ion irradiation transformed the surface of PDMS into a silica-like surface with abundant oxygen functional groups, facilitating the formation of wrinkles in PDMS.