Free-Hanging Microchannel for High Flowrate MEMS Sensors
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Solution Overview
Problem
Existing microelectromechanical system (MEMS) components manufactured using Surface Channel Technology (SCT) are limited in achieving higher flowrates while maintaining low volumes and low pressure drop, which is necessary for applications like liquid chromatography and "Lab-on-a-Chip".
Innovation Solution
The development of a microelectromechanical system component with a free-hanging or free-standing microchannel having a substantially circular cross-section, where the channel diameter is significantly larger than the channel wall thickness, allowing for increased flow range and reduced pressure sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Surface Channel Technology (SCT) is used to manufacture MEMS components, then the channel can be freely shaped with precise manufacturing control, but the channel diameter is limited to around 300 μm and higher flowrates cannot be achieved
Solution Approach 1:
The patent transitions from surface-level channel creation (2D SCT) to bulk substrate etching (3D approach), allowing channels to extend through the entire substrate thickness. This dimensional change enables much larger channel diameters (up to 1 mm or more) while maintaining manufacturing precision through controlled etching processes from both front and back sides of the substrate.
Solution Approach 2:
The manufacturing process is divided into multiple stages: front side etching, back side etching, and selective removal of sacrificial layers. This segmentation allows independent control of channel dimensions and wall thickness, enabling large diameters while maintaining precise geometric control through separate etching steps.
2Productivity
If the channel diameter is increased to achieve higher flowrates, then the flow range improves, but the pressure drop increases and the channel wall becomes thinner
Solution Approach 1:
By etching channels through the bulk substrate rather than creating surface channels, the patent achieves larger diameters that reduce flow resistance and pressure drop. The three-dimensional etching approach allows optimal diameter selection for high flowrate applications while maintaining adequate wall thickness through controlled etching depths from both substrate sides.
Solution Approach 2:
The patent changes the fundamental manufacturing parameter from surface etching depth to bulk etching through the entire substrate. This parameter change enables channel diameters an order of magnitude larger than SCT, directly reducing pressure drop according to the Hagen-Poiseuille equation, while wall thickness is controlled by the etching process parameters.
3Productivity
If the channel diameter is increased, then higher flowrates are possible, but the channel wall thickness becomes insufficient and structural stability decreases
Solution Approach 1:
The etching process is segmented into front-side and back-side operations with a sacrificial layer in between. This allows the channel to be formed as a through-substrate structure with walls defined by the substrate material itself, providing inherent structural strength. The wall thickness is determined by the substrate thickness and etching control, decoupled from the channel diameter.
Solution Approach 2:
The patent utilizes the substrate material (typically silicon or other MEMS-compatible materials) as both the structural support and the channel wall material. This composite approach, where the substrate provides mechanical strength and the etched channels provide fluid transport, enables large diameter channels with adequate wall thickness for structural stability.
4Volume of stationary object
If Surface Channel Technology is used, then low-volume microfluidic flowmeters can be manufactured, but the pressure sensitivity increases and low pressure drop cannot be achieved
Solution Approach 1:
The transition from surface channels to bulk channels creates larger diameter flow paths that significantly reduce pressure drop. The bulk etching approach allows channels to occupy the full substrate thickness, maximizing hydraulic diameter while maintaining compact device footprint, thereby reducing pressure sensitivity.
Solution Approach 2:
Changing the channel formation from surface-level to bulk-through changes the hydraulic geometry parameters. The larger effective diameter and reduced flow path length through the substrate directly reduce pressure drop according to fluid dynamics principles, while the device remains compact due to the thin substrate configuration.
Data Source
AI summary
The invention relates to a microelectromechanical system (MEMS) component or microfluidic component comprising a free-hanging or free-standing microchannel (1), as well as methods for manufacturing such a microchannel, as well as a flow sensor, e.g. a thermal flow sensor or a Coriolis flow sensor, pressure sensor or multi-parameter sensor, valve, pump or microheater, comprising such a microelectromechanical system component or microfluidic component. The MEMS component allows to increase the flow range and/or decrease the pressure drop of for instance a micro Coriolis mass flow meter by increasing the channel diameter, while maintaining its advantages.