MEMS Device with Interdigitated Fingers for Fluid Interaction
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Solution Overview
Problem
Existing MEMS devices have limitations in interacting with ambient fluids due to insufficient effective area and require in-plane movements for efficient interaction, which current technologies, such as comb-like drive structures, fail to adequately address.
Innovation Solution
A MEMS device with a layer stack comprising laterally deflectable elements and interdigitating fingers that form volume-variable sub-cavities, allowing for increased interaction area with ambient fluids through in-plane movement and minimizing electrical capacitance loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If comb-like drive structures are used to move micromirrors in-plane, then the interaction area with ambient fluid is increased, but high electrical capacitance is required for deflection
Solution Approach 1:
The cavity is divided into multiple sub-cavities by the interdigitated fingers, allowing the system to achieve large effective interaction area through segmentation rather than requiring a single large moving structure. This reduces the capacitance burden on any single actuator while maintaining total interaction area.
Solution Approach 2:
The patent transitions from traditional out-of-plane membrane movement to in-plane lateral movement of deflectable elements. This dimensional change enables interaction with ambient fluid through lateral displacement while using electrostatic actuation between interdigitated fingers, avoiding the high capacitance requirements of traditional comb-drive structures.
2Ease of operation
If out-of-plane membrane deflection is used, then simple actuation is achieved, but the effective area for fluid interaction is limited
Solution Approach 1:
The patent employs in-plane lateral movement of deflectable elements within the cavity plane, rather than out-of-plane membrane deflection. This dimensional transition allows the entire cavity area to participate in fluid interaction while maintaining simple electrostatic actuation through the interdigitated finger structure.
Solution Approach 2:
The deflectable elements are designed to move laterally in response to electrostatic forces between interdigitated fingers, creating a dynamic structure that can modulate the volume of sub-cavities. This dynamic in-plane movement provides both simplicity of actuation and large effective interaction area.
3Stability of the object's composition
If plates are arranged to close off a cavity, then structural stability is improved, but the device is not suitable for large volumes
Solution Approach 1:
The cavity is segmented into multiple sub-cavities by vertical walls formed between laterally spaced deflectable elements. This segmentation allows the structure to maintain stability through the vertical walls while achieving large total volume through the cumulative effect of multiple sub-cavities arranged in parallel.
Solution Approach 2:
The patent uses lateral spacing of deflectable elements to create vertical walls that extend through the cavity height, forming sub-cavities in the lateral dimension. This approach enables large total cavity volume while maintaining structural stability through the distributed vertical wall structure.
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
The MEMS device achieves a high degree of interaction with ambient fluids, enabling both actuation and sensing capabilities while maintaining low unwanted electrical capacitance, thus enhancing the effective area utilization and sensitivity.
Implementation Method 1
The laterally deflectable elements can be deformed laterally upon application of an electrical potential
Data Source
AI summary
Proposed is a MEMS device comprising a layer stack having at least one second layer formed between a first layer and a third layer. A cavity is formed in the second layer. The MEMS device further comprises two laterally deflectable elements arranged laterally spaced apart in the cavity. Each of the two laterally deflectable elements comprises a respective end connected to a side wall of the cavity. Additionally, the MEMS device comprises a connecting element connected to the two laterally deflectable elements to couple the movement of the two laterally deflectable elements. A plurality of first fingers are arranged discretely spaced between the two laterally deflectable elements on the side wall of the cavity. Further, a plurality of second fingers are arranged discretely spaced between the two laterally deflectable elements on the connecting element. The plurality of second fingers interdigitate with the plurality of first fingers. Further, the plurality of second fingers are laterally displaceable relative to the plurality of first fingers upon deformation of the two laterally deflectable elements such that the plurality of first fingers and the plurality of second fingers define a plurality of volume variable sub-cavities within the cavity. Each of the plurality of sub-cavities is in contact with an ambient fluid of the MEMS device via a respective opening. In case of adjacent sub-cavities of the plurality of sub-cavities, the respective opening of one sub-cavity of the adjacent sub-cavities is formed in a different layer of the first layer, the second layer and the third layer than the opening of the other sub-cavity of the adjacent sub-cavities.