Pressure Sensor Cavity Heating for Liquid Occlusion Ejection
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Solution Overview
Problem
Liquid occlusion in pressure sensors and microphones of portable electronic devices leads to performance degradation due to airflow blockage and capillary forces, causing false pressure readings and sound obstruction, often exacerbated by particulate protection elements.
Innovation Solution
A two-phase pulsed liquid heating method using a heating element with a high power pulse to create an air pocket within the occluded liquid, followed by a lower power phase to expand the air pocket and expel the liquid, minimizing power consumption and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heating element is used to expel liquid occlusion from the pressure sensor cavity, then liquid occlusion is removed and sensor performance is restored, but power consumption increases
Solution Approach 1:
The heating element operates in periodic pulses rather than continuously. The controller applies heating pulses only when liquid occlusion is detected, allowing the heating element to rest and cool between pulses. This periodic operation significantly reduces average power consumption while maintaining the ability to expel liquid occlusion when needed.
Solution Approach 2:
The heating element exploits the phase transition of water from liquid to vapor. By heating the occluded liquid to its boiling point, the liquid transforms into vapor, which expands in volume and creates pressure to expel the liquid from the sensor cavity. This phase transition mechanism is highly efficient at removing liquid occlusion with minimal energy input compared to mechanical evacuation methods.
2Reliability
If continuous heating is applied to expel liquid occlusion, then liquid is effectively removed, but energy efficiency decreases
Solution Approach 1:
The system uses periodic heating pulses instead of continuous heating. The controller monitors the cavity for liquid occlusion and activates the heating element only when needed, allowing it to remain inactive during normal operation. This on-demand periodic heating maintains effective liquid removal capability while minimizing energy loss during extended operational periods.
Solution Approach 2:
The heating element rapidly heats the occluded liquid to the boiling point in a short time interval, quickly achieving the phase transition and expelling the liquid. This rapid heating approach minimizes the total time the heating element is active, reducing overall energy consumption while ensuring complete liquid removal.
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
Effectively expels liquid occlusion with reduced power consumption, improving sensor performance by maintaining accurate pressure readings and sound transmission.
Implementation Method 1
a heating element configured to heat the occluding liquid with the first power pulse during the first phase to cause an air pocket to form around the heating element and expand the air pocket to break the occluding liquid film
Implementation Method 2
heating at least a portion of a liquid volume inside the cavity to cause an air pocket to form around the heating element by phase change
Implementation Method 3
expand the air pocket to break the occluding liquid film
Data Source
AI summary
Aspects of the subject technology relate to electronic devices with pressure sensors. Pressure sensor occlusion may be mitigated by ejecting occluding liquid with pulsed liquid heating. Processing circuit of the electronic device can obtain pressure sensor data from the pressure sensor and determine that the opening is occluded based at least in part on a change in pressure within a cavity adjacent the opening. The processing circuitry applies a first power pulse to a heating element during a first phase to cause the heating element to form a gas pocket around the heating element by heating at least a portion of a water volume inside the cavity and applies a second power pulse to the heating element during a second phase following the first phase to cause the heating element to expand the gas pocket around the heating element by further heating the water volume inside the cavity.