@article{2111b2ac655d425bafbd3c49d304b757,
title = "Advanced top-down fabrication for a fused silica nanofluidic device",
abstract = "Nanofluidics have recently attracted significant attention with regard to the development of new functionalities and applications, and producing new functional devices utilizing nanofluidics will require the fabrication of nanochannels. Fused silica nanofluidic devices fabricated by top-down methods are a promising approach to realizing this goal. Our group previously demonstrated the analysis of a living single cell using such a device, incorporating nanochannels having different sizes (102-103 nm) and with branched and confluent structures and surface patterning. However, fabrication of geometrically-controlled nanochannels on the 101 nm size scale by top-down methods on a fused silica substrate, and the fabrication of micro-nano interfaces on a single substrate, remain challenging. In the present study, the smallest-ever square nanochannels (with a size of 50 nm) were fabricated on fused silica substrates by optimizing the electron beam exposure time, and the absence of channel breaks was confirmed by streaming current measurements. In addition, micro-nano interfaces between 103 nm nanochannels and 101 μm microchannels were fabricated on a single substrate by controlling the hydrophobicity of the nanochannel surfaces. A micro-nano interface for a single cell analysis device, in which a nanochannel was connected to a 101 μm single cell chamber, was also fabricated. These new fabrication procedures are expected to advance the basic technologies employed in the field of nanofluidics.",
keywords = "Lab-on-a-chip, Micro-nano interface, Nanochannel, Nanofabrication, Nanofluidics, Streaming current, Top-down fabrication",
author = "Kyojiro Morikawa and Yutaka Kazoe and Yuto Takagi and Yoshiyuki Tsuyama and Yuriy Pihosh and Takehiko Tsukahara and Takehiko Kitamori",
note = "Funding Information: fused silica substrates using lithography and etching processes. Although fabrication of them using other fabrication method such as deposition, molding and milling on other substrate materials than other fabrication method such as deposition, molding and milling on other substrate materials than fused silica was reported, it was difficult on fused silica substrate by lithography and etching processes. fused silica was reported, it was difficult on fused silica substrate by lithography and etching In the present study, precise 50 nm square nanochannels were first fabricated on the fused silica processes. In the present study, precise 50 nm square nanochannels were first fabricated on the fused substrate by electron beam lithography and dry etching, employing an electron beam exposure silica substrate by electron beam lithography and dry etching, employing an electron beam exposure time of 0.5 µs/dot after applying an electron beam resist material that had been diluted threefold. time of 0.5 μs/dot after applying an electron beam resist material that had been diluted threefold. Streaming current measurements confirmed the successful fabrication of the nanochannels without Streaming current measurements confirmed the successful fabrication of the nanochannels without channel breaks, indicating that the smallest-ever square nanochannels on a fused silica substrate had channel breaks, indicating that the smallest-ever square nanochannels on a fused silica substrate had been obtained. The first confirmation a pressure-driven flow of liquids in 50 nm channels within a fused been obtained. The first confirmation a pressure-driven flow of liquids in 50 nm channels within a silica nanofluidic device was also directly confirmed. In addition, micro-nano interfaces were fabricated fused silica n3 anofluidic device was also directly confirmed. In ad1dition, micro-nano interfaces were at which 10 nm nanochannels3 were successfully connected to 10 µm microchannels.1 In this process, fabricated at which 10 nm nanochannels were successfully connected to 10 μm microchannels. In a photoresist was uniformly applied to an HDMS-modified substrate incorporating nanochannels by this process, a photoresist was uniformly applied to an HDMS-modified substrate incorporating controlling the hydrophobicity of the nanochannel surfaces. This represents a promising approach nanochannels by controlling the hydrophobicity 1 2 of the nanochannel surfaces. This represents a to generating micro-nano interfaces using 10 –10 nm nanochannels.1 F2inally, a micro-nano interface promising approach to generating micro-nano interfaces using 10 –10 nm nanochannels. Finally, 1 a intended for single cell analysis was fabricated by connecting a nanochannel to a 10 mm single cell micro-nano interface intended for single cell analysis was fabricated by connecting a nanochannel to cham1 ber. These results are first fabrication of micro-nano interfaces on a single fused silica substrate a 10 mm single cell chamber. These results are first fabrication of micro-nano interfaces on a single fabricated by lithography and etching methods. The procedures reported herein are expected to allow fused silica substrate fabricated by lithography and etching methods. The procedures reported herein the design of new functional devices and to provide new synthetic techniques for nanofluidics. are expected to allow the design of new functional devices and to provide new synthetic techniques Authorfor nanofContributions:luidics. Conceptualization,K.M.andT.K.;experiments,K.M.,Y.T.(YutoTakagi),Y.T.(YoshiyukiTsuyama), Y.P. and T.T.; writing, K.M. and Y.K.; supervision, Y.K., T.T. and T.K. All authors have read and agreed to the published Author Contributions: Conceptualization, K.M. and T.K.; experiments, K.M., Y.T. (Yuto Takagi), Y.T. version of the manuscript. (Yoshiyuki Tsuyama), Y.P. and T.T.; writing, K.M. and Y.K.; supervision, Y.K., T.T. and T.K. All authors have Funding: JSPS KAKENHI (grant number JP19K15417) and the Core Research for Evolutional Science and read and agreed to the published version of the manuscript. Technology (CREST) program of the Japan Science and Technology Agency (JST) (grant number JPMJCR14G1). Funding: JSPS KAKENHI (grant number JP19K15417) and the Core Research for Evolutional Science and Acknowledgments: Fabrication and characterization facilities were provided in part by the Academic Consortium for Nano and Micro Fabrication associated with the University of Tokyo, Tokyo Institute of Technology, Keio University and Waseda University, and by the Advanced Characterization Nanotechnology Platform of the Acknowledgments: Fabrication and characterization facilities were provided in part by the Academic University of Tokyo, supported by the Nanotechnology Platform of the Ministry of Education, Culture, Sports, ScienceConsortiuandmTfor Nano and Micro Fechnology (MEXT), Japan.abrication associated with the University of Tokyo, Tokyo Institute of Technology, Keio University and Waseda University, and by the Advanced Characterization Nanotechnology Conflicts of Interest: The authors declare no conflict of interest. Platform of the University of Tokyo, supported by the Nanotechnology Platform of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Publisher Copyright: {\textcopyright} 2020 by the authors. Licensee MDPI, Basel, Switzerland.",
year = "2020",
month = nov,
doi = "10.3390/mi11110995",
language = "English",
volume = "11",
journal = "Micromachines",
issn = "2072-666X",
publisher = "Multidisciplinary Digital Publishing Institute (MDPI)",
number = "11",
}