title: Hollow Microtube Resonators via Silicon Self-Assembly toward Subattogram Mass Sensing Applications.
abstract: Fluidic resonators with integrated microchannels (hollow resonators) are attractive for mass, density, and volume measurements of single micro/nanoparticles and cells, yet their widespread use is limited by the complexity of their fabrication. Here we report a simple and cost-effective approach for fabricating hollow microtube resonators. A prestructured silicon wafer is annealed at high temperature under a controlled atmosphere to form self-assembled buried cavities. The interiors of these cavities are oxidized to produce thin oxide tubes, following which the surrounding silicon material is selectively etched away to suspend the oxide tubes. This simple three-step process easily produces hollow microtube resonators. We report another innovation in the capping glass wafer where we integrate fluidic access channels and getter materials along with residual gas suction channels. Combined together, only five photolithographic steps and one bonding step are required to fabricate vacuum-packaged hollow microtube resonators that exhibit quality factors as high as ∼ 13,000. We take one step further to explore additionally attractive features including the ability to tune the device responsivity, changing the resonator material, and scaling down the resonator size. The resonator wall thickness of ∼ 120 nm and the channel hydraulic diameter of ∼ 60 nm are demonstrated solely by conventional microfabrication approaches. The unique characteristics of this new fabrication process facilitate the widespread use of hollow microtube resonators, their translation between diverse research fields, and the production of commercially viable devices.
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Joohyun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Jungki
authors.initials: J
authors.lastname: Song
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Kwangseok
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Seokbeom
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Jihwan
authors.initials: J
authors.lastname: Song
authors.affiliation: Department of Mechanical Design and Production Engineering, Konkuk University , Seoul 143-701, Republic of Korea.
authors.forename: Namsu
authors.initials: N
authors.lastname: Kim
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 2V4, Canada.
authors.forename: M Faheem
authors.initials: MF
authors.lastname: Khan
authors.affiliation: Department of Mechanical Engineering, Hangzhou Dianzi University , Hangzhou, 310018, China.
authors.forename: Linan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: School of Mathematics and Statistics, The University of Melbourne , Victoria, 3010, Australia.
authors.forename: John E
authors.initials: JE
authors.lastname: Sader
authors.affiliation: Department of Mechanical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Keunhan
authors.initials: K
authors.lastname: Park
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Dongchoul
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 2V4, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Thundat
authors.affiliation: Department of Mechanical Engineering, Sogang University , Seoul, 121-742, Republic of Korea.
authors.forename: Jungchul
authors.initials: J
authors.lastname: Lee
keywords: Fluidic resonators; mass sensors; microtube; self-assembly; silicon-on-nothing (SON)