MEMS Coriolis Flow Sensor Tube Resonance Clamping Losses
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Solution Overview
Problem
MEMS-based Coriolis microfluidic devices face mechanical losses due to the attachment of the resonating tube to a substrate, which limits their sensitivity and requires large packaging masses to dissipate energy and isolate from external stress and vibration, hindering precise measurements in industries like medical, energy, and chemical fields.
Innovation Solution
The device features a micromachined microfluidic system with a tube structure configured to vibrate in a plane parallel to the substrate, minimizing clamping losses by having tube portions that resonate approximately 180 degrees out of phase, allowing for reduced mechanical losses and potentially using less expensive packaging materials and processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the resonating tube is attached to a substrate for structural support, then the device can be fabricated using standard MEMS processes, but mechanical losses occur due to clamping losses at the attachment points
Solution Approach 1:
The patent employs asymmetric support structures where the resonating tube is attached at non-symmetric positions or with asymmetric stiffness characteristics. This asymmetry allows the tube to vibrate in a mode that minimizes coupling with the substrate, thereby reducing clamping losses while maintaining structural support for standard MEMS fabrication processes.
2Measurement precision
If large packaging masses are used to dissipate mechanical energy and isolate from external stress and vibration, then measurement precision is improved, but device size and complexity increase
Solution Approach 1:
The patent extracts the resonating tube from direct contact with the substrate by suspending it on flexible supports or beams. This extraction eliminates the need for large packaging masses to isolate the tube from external stress and vibration, as the tube is already mechanically decoupled from the substrate while remaining supported for fabrication purposes.
3Stability of the object's composition
If the resonating tube is rigidly attached to the substrate, then structural stability is maintained, but sensitivity of the device decreases due to energy dissipation
Solution Approach 1:
The patent uses flexible support structures such as thin beams or membranes to attach the resonating tube to the substrate. These flexible supports provide sufficient structural stability to maintain the device composition while allowing the tube to vibrate with minimal energy dissipation, thereby preserving measurement sensitivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the sensitivity of the MEMS device, enables the use of less expensive packaging, and reduces squeeze film damping, potentially allowing for disposable units and improved performance under mechanical stresses without compromising accuracy.
Implementation Method 1
The drive electrode can be, for example, capacitively coupled to the freestanding portion of the tube for capacitively (electrostatically) driving the freestanding portion at or near resonance
Implementation Method 2
the sensing electrodes sense (e.g., capacitively, optically, etc.) the deflection of the resonating tube relative to the substrate
Implementation Method 3
as the freestanding portion is driven at or near resonance by the drive electrode, the sensing electrodes sense a twisting motion of the freestanding portion, referred to as the Coriolis effect, about the axis of symmetry of the freestanding portion. The degree to which the freestanding portion twists (deflects) during a vibration cycle as a result of the Coriolis effect can be correlated to the mass flow rate of the fluid flowing through the tube
Implementation Method 4
The performance of the device is improved by configuring the resonating structure to minimize mechanical losses resulting from the mechanical energy of the resonating structure being dissipated to a supporting substrate
Implementation Method 5
clamping losses occur as a result of the tube's substrate anchor (attachment) to the MEMS substrate being stressed by tube displacement. A fraction of the vibration energy is lost from the tube though wave propagation into the MEMS substrate
Data Source
AI summary
Fluidic systems and methods of determining properties of fluids flowing therein. The fluidic systems and methods make use of a micromachined device that determines at least one property of the fluid within the system. The micromachined device includes a base structure on a substrate and a tube structure extending from the base structure and spaced apart from a surface of the substrate. The tube structure has at least one pair of geometrically parallel tube portions substantially lying in a plane, and at least one continuous internal passage defined at least in part within the parallel tube portions. A drive element induces vibrational movement of the tube structure in the plane of the tube structure and induces resonant vibrational movements in the tube portions in the plane of the tube structure. A sensing element senses deflections of each tube portion in the plane of the tube structure.