The surface modification is indispensable to facilitate new functional applications of micro/nanofluidics devices. Among many modification techniques developed so far, the photo-induced chemical modification is the most versatile method in terms of robustness, process simplicity, and feasibility of chemical functionality. In particular, the method is useful for closed spaces, such as post-bonded devices. However, the limitation by optical diffraction limit is still a challenging issue in scaling down the pattern sizes to nanoscale. Here, we demonstrated a novel surface modification on sub-100 nm scale utilizing the novel optical near-field (ONF) generated on nanostructures of photocatalyst (TiO2). The minimum pattern size of 40 nm, which was much smaller than diffraction limit, was achieved using a visible light source (488 nm) and a conventional irradiation setup. The controllability of pattern size by light intensity, the feasibility of functionality, and the non-contact working mode have impacts on surface patterning of post-bonded micro/nanofluidics devices. It is also worthy to note that our results verified for the first time the ONF on nanostructures of non-metal materials and its ability to manipulate the chemical reaction on nanoscale.
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This work was partially supported by JSPS Core-to-Core Program and the Grant-in-Aid for Specially Promoted Research. We also would like to thank to the Research Hub for Nano Characterization Center at the University of Tokyo for SEM measurement.
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Le, T.H.H., Mawatari, K., Pihosh, Y. et al. Novel sub-100 nm surface chemical modification by optical near-field induced photocatalytic reaction. Microfluid Nanofluid 17, 751–758 (2014). https://doi.org/10.1007/s10404-014-1361-7
- Surface modification on nanoscale
- Modification of bonded chip
- Optical near-field
- Photocatalytic chemical modification