Abstract
Micro-electro-mechanical membranes having nanoscale holes were developed, to be used as a nanofluidic sample inlet in novel analytical applications. Nanoscopic holes can be used as sampling points to enable a molecular flow regime, enhancing the performance and simplifying the layout of mass spectrometers and other analytical systems. To do this, the holes must be placed on membranes capable of consistently withstanding a pressure gradient of 1 bar. To achieve this goal, a membrane-in-membrane structure was adopted, where a larger and thicker membrane is microfabricated, and smaller sub-membranes are then realized in it. The nanoscopic holes are opened in the sub-membranes. Prototype devices were fabricated, having hole diameters from 300 to 600 nm, a membrane side of 80 μm, and a simulated maximum displacement of less than 150 nm under a 1 bar pressure gradient. The obtained prototypes were tested in a dedicated vacuum system, and a method to calculate the effective orifice diameter using gas flow measurements at different pressure gradients was implemented. The calculated diameters were in good agreement with the target diameter sizes. Micro-electro-mechanical technology was successfully used to develop a novel micromembrane with nanoscopic holes, and the fabricated prototypes were successfully used as a gas inlet in a vacuum system for mass spectrometry and other analytical systems.
Highlights
Nanoscale fluidics are key to enable a range of novel fluidic devices [1]
Micro-electro-mechanical technology was successfully used to develop a novel micromembrane with nanoscopic holes, and the fabricated prototypes were successfully used as a gas inlet in a vacuum system for mass spectrometry and other analytical systems
To overcome the above-mentioned limitations, in the present work, we report the development of freestanding MEMS membranes with nanoscale holes, using a novel membrane-in-membrane structure: A thick support membrane was designed, where smaller sub-membranes were fabricated, having nanoscopic holes
Summary
Nanoscale fluidics are key to enable a range of novel fluidic devices [1]. In recent years, nanoscale holes have been used as sample inlets for the development of high-performance spectrometer gas sensors, leveraging the combination of nano technologies with ultra-high vacuum (UHV) techniques.There are solid reasons to operate at the nanoscale level for analytical purposes. Nanoscale holes have been used as sample inlets for the development of high-performance spectrometer gas sensors, leveraging the combination of nano technologies with ultra-high vacuum (UHV) techniques. Gas analyzers (GAs), multi gas analyzers, and in specific cases, gas chromatograph mass spectrometers (GC-MS) can operate from a few mbar up to atmospheric pressure to monitor processes in the semiconductors industry, refrigeration industry, and in leak detection fields. Such GAs are submitted to the typical MS vacuum constraints, which strongly depend on inlet sample flows and vacuum systems. A great improvement in system simplification [2,3,4,5] is possible by using nanometer-scale orifices [5] as sampling points and smart gas interfaces toward atmospheric pressure
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