Micromachined Capacitive Flow Sensor for Consistent Puff Actuation
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Solution Overview
Problem
Existing airflow sensors in electronic cigarettes lack consistency in actuation pressure due to manufacturing tolerances, leading to inconsistent power supply control for heating elements, especially when using capacitive sensing components.
Innovation Solution
A micromachined capacitive flow sensor with a movable membrane and perforated backplate forms a variable capacitor, where the capacitance varies non-linearly with airflow pressure, acting as a switch to control power supply to heating elements based on user puffing or smoking pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional airflow sensors are used in electronic cigarettes, then power supply control for heating elements can be achieved, but manufacturing tolerances cause inconsistency in actuation pressure
Solution Approach 1:
The patent changes the sensing mechanism from resistive to capacitive, fundamentally altering the physical parameter being measured. The capacitive sensor measures changes in capacitance caused by airflow-induced membrane displacement, rather than relying on resistive changes that are sensitive to manufacturing tolerances. This parameter change enables consistent actuation pressure detection.
Solution Approach 2:
The patent replaces the mechanical/resistive sensing system with a capacitive sensing system. Instead of using resistive elements that vary with manufacturing precision, the invention uses electrostatic capacitance changes resulting from membrane displacement due to airflow pressure, thereby substituting a mechanical measurement approach with an electrical field-based approach that is less sensitive to manufacturing variations.
2Measurement precision
If capacitive sensing components are used to improve sensitivity, then detection capability increases, but consistency in actuation pressure control deteriorates
Solution Approach 1:
The patent introduces a movable membrane that dynamically responds to airflow pressure by displacing and changing the capacitance of the sensing element. This dynamic mechanical response translates airflow pressure into measurable capacitance changes, providing both high sensitivity and consistent actuation pressure detection. The membrane's physical displacement serves as an intermediate that converts pressure into an electrical signal with high fidelity.
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 sensor provides precise control over power supply to heating elements by exhibiting a non-linear capacitance change, ensuring consistent actuation and deactuation based on user airflow, enhancing the efficiency and reliability of electronic cigarettes.
Implementation Method 1
The movable membrane, the gas gap and the perforated backplate form a variable capacitor whose capacitance varies with movement of the membrane relative to the perforated backplate
Implementation Method 2
the gas flow pressures the movable membrane causing it to deflect towards the perforated backplate
Data Source
AI summary
A micromachined capacitive flow sensor includes a movable membrane having one or more venting holes and a perforated backplate having perforation holes or through holes. A gas gap (such as an air gap) is formed between the movable membrane and the perforated backplate. The movable membrane, the gas gap and the perforated backplate form a variable capacitor whose capacitance varies with a movement of the membrane relative to the perforated backplate. The sensor may be used to manufacture a packaged flow sensor product which may find numerous applications, for example, using the product as a switch to turn on and off the electric power to the heating elements of the aerosol delivery device in response to the puff and/or smoking action of the user.