Trapped Fluid MEMS Acoustic Sensor Architecture
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Solution Overview
Problem
Current acoustic sensors lack the sensitivity and bandwidth to effectively operate in both air and submerged environments while maintaining low power consumption and compact size, especially for applications like unattended sensors and medical devices.
Innovation Solution
A micromachined trapped-fluid acoustic sensor system with a cochlear-like architecture, incorporating a novel trapped-fluid architecture and capacitive sensing, which separates the acoustic input from the sensing location, allowing for submerged operation without compromising bandwidth and sensitivity, and features a unique geometry that enhances sensitivity through mass-loading and damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic sensors are designed for high sensitivity and bandwidth, then sensing performance improves, but device size and power consumption increase
Solution Approach 1:
The patent implements a nested structure where the sensing membrane is positioned within a fluid-filled chamber, and the entire sensor assembly is integrated into a compact package. The trapped fluid is contained within a sealed chamber that surrounds the sensing elements, creating a nested configuration that achieves high sensitivity without proportionally increasing device volume.
Solution Approach 2:
The patent utilizes a trapped fluid (liquid or gas) within a sealed chamber to transmit acoustic energy to the sensing membrane. The fluid-filled chamber acts as an acoustic waveguide that delivers sound waves to the sensing elements with minimal loss, enabling high sensitivity and bandwidth while maintaining a compact form factor through hydraulic/pneumatic transmission mechanisms.
2Adaptability or versatility
If acoustic sensors are designed for submerged operation, then adaptability to marine environments improves, but bandwidth and sensitivity are compromised
Solution Approach 1:
The patent introduces a trapped fluid within a sealed chamber as an intermediary medium between the external acoustic field and the sensing membrane. This intermediary fluid transmission system allows the sensor to operate in submerged environments while maintaining acoustic coupling to the sensing elements, thereby preserving bandwidth and sensitivity that would otherwise be compromised by direct water exposure.
Solution Approach 2:
The patent employs a flexible sensing membrane that can be sealed within a rigid chamber containing trapped fluid. The membrane remains acoustically active while being protected from direct contact with the external marine environment, enabling submerged operation without sacrificing performance. The thin film membrane transmits acoustic energy efficiently while maintaining the sealed fluid environment.
3Measurement precision
If acoustic sensors use complex mechanical processes for frequency separation, then frequency analysis capability improves, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical frequency separation processes with electronic signal processing. Instead of using mechanical structures to physically separate frequencies, the system uses electronic filters and processors to analyze frequency content, thereby achieving sophisticated frequency analysis capability while reducing mechanical complexity.
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 system achieves sensitivities competitive with commercial hydrophones, with up to 20 dB higher sensitivity and maintains a 10 kHz bandwidth, enabling efficient acoustic sensing in both air and submerged conditions with low power consumption and compact form factor.
Implementation Method 1
The liquid transfers acoustic energy from the input membrane to the conductive membrane
Implementation Method 2
The input membrane is configured to vibrate in response to an excitation from acoustic energy
Implementation Method 3
The conductive membrane is configured to vibrate in response to an excitation from acoustic energy in the liquid adjacent the conductive membrane
Data Source
AI summary
Silicon and glass micromachined (MEMS) acoustic sensors incorporating trapped-liquid architectures are disclosed. The trapped liquid serves as an acoustic transmission medium allowing the input port to the system to be physically separated from the sensing location. The trapped liquid interacts with a conductive, flexible sensing membrane. Sound pressure waves enter the trapped liquid through an input membrane, travel to the sensing membrane, and excite vibrations of the sensing membrane. The vibrations of the sensing membrane are measured using on-chip capacitive sensing. The capacitive sensing structure is formed by the conductive sensing membrane and a fixed conducting top electrode. As the gap between the conductive sensing membrane and the fixed top electrode varies, the capacitance varies, leading to an electrical signal which is the electrical output of the system.