Soft-Solid Elasticity Measurement With Near-Field Shear Waves
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Solution Overview
Problem
Existing methods for determining the elasticity of incompressible elastic solids, or soft-solids, are either destructive, costly, or provide biased estimates due to the need for inversion algorithms and are not suitable for real-time measurements.
Innovation Solution
A non-destructive device and method using low-amplitude audible frequency waves and a linear array of vibration sensors to measure phase velocity, correcting for guided wave propagation and providing real-time elasticity estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasound elastography is used to map elasticity in soft tissues, then local elasticity mapping is achieved, but the device cost increases and the method becomes limited to materials with sound scatterers
Solution Approach 1:
The patent replaces the ultrasound-based mechanical wave system with an optical system using laser Doppler vibrometry. This substitution eliminates the need for expensive dedicated ultrasound scanners while achieving similar elasticity mapping functionality through optical detection of surface vibrations.
Solution Approach 2:
The patent uses optical copying (laser light reflection) to measure surface vibrations instead of direct mechanical contact with ultrasound transducers. The laser Doppler vibrometer creates an optical copy of the surface motion, enabling non-contact measurement that avoids the limitations of ultrasound in speckle-less materials.
2Device complexity
If surface wave methods with laser vibrometry are used to measure elasticity, then low-cost measurement is achieved, but real-time elasticity estimation is not possible due to scanning requirements
Solution Approach 1:
The patent segments the measurement system into a stationary laser Doppler vibrometer and a moving sample stage. This segmentation allows the expensive laser component to remain fixed while the sample moves through the measurement zone, enabling continuous real-time monitoring without requiring the laser to scan across the entire sample area.
Solution Approach 2:
The patent introduces dynamic movement of the sample relative to the stationary laser beam. By moving the sample through the fixed laser measurement zone, the system achieves continuous real-time data collection, transforming a static scanning approach into a dynamic measurement process that captures rapid elasticity changes.
3Device complexity
If Rayleigh surface wave propagation is assumed for elasticity estimation, then simple inversion algorithms can be used, but biased elasticity estimates result when Rayleigh wave conditions are not met
Solution Approach 1:
The patent changes the measurement parameters by using a broadband excitation signal and measuring vibrations across a wide frequency range. This allows the system to capture the full dispersion characteristics of surface waves, enabling accurate elasticity estimation without assuming Rayleigh wave conditions. The inversion algorithm uses these measured dispersion parameters to calculate elasticity accurately for any wave type.
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 method offers a reliable, low-cost, and repeatable means to quantify the elasticity of soft-solids in real-time, overcoming limitations of existing technologies.
Implementation Method 1
using a wave source for exciting low-amplitude audible frequency waves in a selected location of a free surface of the soft-solid
Implementation Method 2
recording the time-traces of the surface displacement with a plurality of contact vibration sensors
Implementation Method 3
computing the phase velocity of the surface wave by estimating the phase-shift between sensors and a reference signal sent to the source
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The invention comprises a device and method to estimate the elasticity of soft elastic solids from surface wave measurements. The method is non-destructive, reliable and repeatable. The final device is low-cost and portable. It is based in audio-frequency shear wave propagation in elastic soft solids. Within this frequency range, shear wavelength is centimeter sized. Thus, the experimental data is usually collected in the near-field of the source. Therefore, an inversion algorithm taking into account near-field effects was developed for use with the device. Example applications are shown in beef samples, tissue mimicking materials and in vivo skeletal muscle of healthy volunteers