Ear-Canal Capacitive Ultrasound Transducers for Air-Coupled Sensing
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Solution Overview
Problem
Conventional ultrasound transducers require coupling fluids to match impedance, which is not feasible for certain biological membranes, and making them smaller complicates achieving sufficient intensity, spatial coherence, and phase stability.
Innovation Solution
Development of capacitive ultrasound transducers with a base designed for the external ear canal, featuring a plurality of capacitive elements with specific performance characteristics, including angular beam spread and attenuation loss, to characterize fluids behind the eardrum without coupling fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the transducer size is reduced, then the scattering of ultrasound with air is decreased and coherence is improved, but the intensity, spatial coherence, and phase stability become insufficient
Solution Approach 1:
The transducer is divided into multiple individual capacitive elements (e.g., 6-12 elements) arranged in an array on the base. Each element operates independently but contributes to the overall ultrasound signal, allowing the small form factor to achieve sufficient intensity and phase stability through collective operation while maintaining low scattering characteristics.
Solution Approach 2:
Multiple capacitive elements are nested within the small base structure designed for the external ear canal. The elements are arranged in a compact configuration that maximizes their collective ultrasound output while maintaining the small overall dimensions needed to reduce air scattering and improve coherence.
2Reliability
If conventional ultrasound transducers are used, then impedance matching is achieved through coupling fluids, but the use of coupling gels is not feasible for certain biological membranes
Solution Approach 1:
The patent uses air as an intermediary medium instead of coupling fluids. The capacitive transducer elements are designed to operate effectively through air coupling, eliminating the need for coupling gels that cannot be used on certain biological membranes. The small size of the elements and their capacitive design enable sufficient ultrasound transmission through air to characterize materials on the other side of membranes.
Solution Approach 2:
The transducer design changes the operating parameters by using capacitive elements with specific resonant frequencies (1.0-3.0 MHz) and small dimensions (10-100 microns diameter) that are optimized for air-coupled operation. This allows the transducer to achieve adequate intensity and phase stability through air without requiring impedance-matching coupling fluids.
3Area of stationary object
If the base dimension is reduced to fit within the external ear canal, then the device can access confined spaces, but the transducer performance may be compromised
Solution Approach 1:
The transducer function is segmented into multiple small capacitive elements that collectively provide the required ultrasound output. Each element is small (10-100 microns) to fit within the ear canal constraints, but the array of multiple elements (at least 6) working together maintains sufficient intensity, spatial coherence, and phase stability for reliable material characterization.
Solution Approach 2:
Multiple capacitive elements are merged into a single functional unit mounted on the base. The combined output of all elements provides the necessary ultrasound intensity and phase stability that would be difficult to achieve with a single element of the same small size, thereby maintaining transducer performance within the size constraints of the external ear canal.
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 transducers provide sufficient intensity and phase stability for characterizing fluids, enabling non-contact measurement of membrane dynamics and fluid properties, such as viscosity, with improved spatial coherence and reduced scattering.
Implementation Method 1
measuring a reflected ultrasound signal using an air-coupled transducer
Implementation Method 2
Conventional ultrasound transducers may need to be used with a coupling fluid to match an impedance of a material to be characterized to an ultrasound transducer because the typical medium between the material and the transducer, such as air, may have an acoustic impendence with significant mis-match to a transducer and/or a material to be measured
Implementation Method 3
measuring a reflected ultrasound signal
Data Source
AI summary
An ultrasound transducer may include: a plurality of capacitive ultrasound transducer elements; and a base having a largest dimension sized and shaped to be disposed with an external ear canal, wherein the plurality of capacitive ultrasound transducers is mounted on the base. Each capacitive ultrasound transducer element and the ultrasound transducer are specifically constructed to achieve select desired performance characteristics. The ultrasound transducer may have an angular beam spread through a gaseous medium of greater than 15 degrees and an attenuation loss through the gaseous medium of greater than 10 dB measured at a distance 12.5 mm to 25 mm along a primary transmission axis of the ultrasound transducer. The ultrasound transducer may be particularly useful for characterizing fluid behind an ear drum to diagnose otitis media.