Waterproof MEMS Button with Capacitive Force Sensing
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Solution Overview
Problem
Current waterproof input devices for portable electronic devices face challenges such as large dimensions that interfere with miniaturization, complex manufacturing and assembly, wear and aging of sealing elements, and high power consumption, which affect battery life.
Innovation Solution
A MEMS button device with a capacitive strain sensor and ASIC processing circuit, integrated into a compact design using a flexible membrane and conductive paths, eliminating the need for external sealing elements and reducing power consumption by using low biasing voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sealing elements (O-rings) are integrated during assembly to prevent water infiltration, then waterproofing is achieved, but device dimensions increase and manufacturing complexity increases
Solution Approach 1:
The patent removes the separate sealing element (O-ring) from the assembly and integrates the sealing function directly into the button structure itself. The button includes a protruding portion that extends through the housing and forms an integrated seal, eliminating the need for additional sealing components and reducing assembly complexity while maintaining waterproofing.
Solution Approach 2:
The sealing function is merged with the button structure. The button's protruding portion is designed to form both the mechanical input interface and the waterproof seal simultaneously, combining multiple functions into a single component rather than using separate elements for button operation and sealing.
2Reliability
If traditional sealing elements (O-rings) are integrated during assembly to prevent water infiltration, then waterproofing is achieved, but device dimensions increase
Solution Approach 1:
The separate sealing element is extracted and its function is integrated into the button, eliminating the additional space required for separate sealing components and reducing overall device dimensions while maintaining the waterproof barrier.
3Measurement precision
If piezoresistive strain sensors are used to detect user commands, then force detection is achieved, but power consumption increases
Solution Approach 1:
The patent replaces the piezoresistive strain sensor with a capacitive sensing mechanism. The button structure includes conductive elements that form capacitive sensors, which detect applied force through capacitance changes rather than resistance changes, resulting in lower power consumption while maintaining force detection capability.
4Measurement precision
If flexible elements and stress sensors are used in the button structure, then force detection is achieved, but device complexity increases
Solution Approach 1:
The button structure is designed to serve multiple functions simultaneously. The protruding portion of the button acts as both the mechanical input interface and the capacitive sensing element, eliminating the need for separate flexible elements and stress sensors, thereby reducing structural complexity while maintaining force detection capability.
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 button device provides durable waterproofing, small dimensions, low power consumption, and accurate force detection, enhancing the usability and battery life of portable electronic devices while maintaining sensitivity and accuracy.
Implementation Method 1
The MEMS device comprises a capacitive strain sensor configured to detect a variation of capacitance value caused by an applied force
Implementation Method 2
a variation of capacitance value caused by an applied force acting on the deformable portion
Data Source
AI summary
A button device includes a MEMS sensor having a MEMS strain detection structure and a deformable substrate configured to undergo deformation under the action of an external force. The MEMS strain detection structure includes a mobile element carried by the deformable substrate via at least a first and a second anchorage, the latter fixed with respect to the deformable substrate and configured to displace and generate a deformation force on the mobile element in the presence of the external force; and stator elements capacitively coupled to the mobile element. The deformation of the mobile element causes a capacitance variation between the mobile element and the stator elements. Furthermore, the MEMS sensor is configured to generate detection signals correlated to the capacitance variation.