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.

Electrophoresis assisted time-of-flow mass spectrometry using hollow nanomechanical resonators

“…Oxide tube resonators were released by a combination of DRIE and SF 6 etching to minimize undercuts. Finally, suspended HNRs were covered with a glass wafer and diced into single chips which could be individually mounted and used in a custom vacuum holder 17 offering off-chip vacuum of ~10 −5  Torr with integrated microfluidic feed-throughs.…”

“…16 . Hollow nanomechanical resonators (HNR) recently developed via silicon self-assembly in our group 17 would be ideal once they are combined with a separation technique that requires minimum external setup. Towards this goal, we have developed a simple standalone system that can be packaged into a portable platform.…”

Bioinspired Electronics for Artificial Sensory Systems

“…Another strategy is to measure the deflection capacitance of the piezoelectric/piezoresistive substrate consisting the hairs for the detection of directionality of vibrations . In addition, the resonance frequency of graphene, CNTs, piezoelectric, silicon, and gallium nitride cantilevers can be tuned to selectively detect ultrasound vibrations, with tunable frequencies ranging 20 kHz to several GHz. They can measure nano‐ to picoscale of force by measuring the changes of resonance frequency according to mechanical oscillation or bending.…”

Deep learning–based inverse method for layout design

“…Recently an innovative usage of this mechanism in microfabrication was proposed. It has been shown that buried cavities/microchannels can be self-assembled simply by annealing a prestructured silicon wafer at high temperature [43,44], without masks and bonding process. This technique also allows monolithic integration of MEMS-COMS [44], thus avoiding the material-and process-incompatibility issues inherent in the traditional integration schemes.…”