Elucidating the effect of boundary curvature on the wrinkling of thin suspended films by theory and experiment

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We synthesized ultra-thin nanocrystalline diamond (NCD) films on Corning Lotus NXT glass substrates with microwave plasma-enhanced chemical vapor deposition. We patterned these films through direct femtosecond laser writing. We accidentally found that nanochannels could be made between the glass substrate and the nanocrystalline diamond film at relatively low laser pulse energies. At relatively high laser pulse energies, portions of the film could be removed, which was our initial goal. Techniques such as focused ion beam milling and electron-beam lithography are currently used to fabricate open nanochannels that are sealed by intricate processes. Manufacturing nanochannel-based devices by such traditional methods is therefore complex, expensive, and time-consuming, hindering progress in the field. Our method for nanochannel manufacturing overcomes such issues and consequently has a high-impact potential. We further investigated the mechanism behind our method and demonstrated that the nanochannels conduct water by fabricating a nanofluidic device. A patent will be filed in April 2023. Immediately after that, we will submit a manuscript to an international journal.In parallel, we also found new phenomena in the wrinkling of NCD films that are compressively strained after deposition and partly released from the glass substrate through substrate etching. Boundary curvature is observed to play a role in the wrinkling of these films, which follows our hypothesis. However, we found that the amount of substrate etched also plays a crucial role.