Soft Tissue Characterization via Nonlinear Viscoelastic Analysis
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Solution Overview
Problem
Current systems lack an efficient method for characterizing soft materials and biological tissues, particularly in terms of nonlinear behavior and time dependency, which is crucial for applications like minimally invasive surgery and robotic tactile sensing, due to the complexity of nonlinear viscoelasticity and the inability to accurately detect mechanical properties such as nonlinear elastic modulus and dissipation functions.
Innovation Solution
A characterization system comprising three main subsystems: an analyzer, mechanisms, and a controller, which applies nonlinear hyperelasticity and viscoelasticity analyses to deform and measure soft materials, including biological tissues, using a combination of hyperelastic and viscous elements to account for time-dependent behavior, with mechanisms driven by a DC servo motor and controlled to maintain constant deformation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional linear analysis methods are used to characterize soft materials, then the analysis process is simple, but the measurement precision of nonlinear mechanical properties deteriorates
Solution Approach 1:
The patent transforms the characterization approach by changing the analysis parameters from linear to nonlinear frameworks. It employs nonlinear hyperelasticity models (e.g., Mooney-Rivlin, Ogden models) and nonlinear viscoelasticity models (e.g., Prony series) to accurately capture the complex mechanical behavior of soft materials, thereby improving measurement precision without excessive complexity increase
Solution Approach 2:
The patent introduces time-dependent dynamic analysis to characterize viscoelastic behavior. By implementing creep tests, relaxation tests, and dynamic mechanical analysis, the system captures the evolving mechanical properties of soft materials under different loading rates and time conditions, enabling accurate measurement of nonlinear viscoelastic parameters
2Device complexity
If time-independent elastic models are used, then the analysis is straightforward, but the reliability of characterizing time-dependent soft materials deteriorates
Solution Approach 1:
The patent employs composite modeling approaches by combining hyperelastic elements (to capture instantaneous elastic response) with viscous elements (to capture time-dependent behavior). This composite constitutive model framework, integrating nonlinear elasticity and viscoelasticity theories, reliably characterizes the full spectrum of time-dependent soft material behavior
Solution Approach 2:
The patent performs preliminary characterization tests (creep tests, relaxation tests, cyclic loading tests) to determine material-specific parameters before applying the nonlinear viscoelastic models. This preliminary action enables accurate calibration of model parameters such as equilibrium modulus, instantaneous modulus, and relaxation times, ensuring reliable characterization
3Device complexity
If simple deformation measurements are used, then the measurement system is simple, but the measurement precision of nonlinear mechanical properties deteriorates
Solution Approach 1:
The patent extends measurements from simple uniaxial deformation to multi-dimensional deformation states. By implementing biaxial testing, planar shear, and complex loading paths, the system captures the full nonlinear stress-strain response of soft materials, enabling precise determination of hyperelastic and viscoelastic parameters through dimensional enrichment of the measurement space
Solution Approach 2:
The patent implements real-time feedback measurement systems that continuously monitor deformation, stress, and material response during testing. This feedback enables dynamic adjustment of loading conditions and accurate capture of transient nonlinear behavior, improving measurement precision through closed-loop control and real-time data acquisition
4Ease of operation
If human touch sensing is used, then the system is intuitive, but the measurement precision and versatility deteriorate
Solution Approach 1:
The patent replaces human tactile sensing with instrumented mechanical testing systems equipped with load cells, displacement sensors, and force transducers. This substitution provides objective, quantifiable measurements of mechanical properties with high precision, capturing parameters such as elastic modulus, viscosity, and energy dissipation that are beyond human sensory capabilities
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 effectively characterizes soft materials and biological tissues by accurately measuring nonlinear mechanical properties, enabling precise interaction and diagnosis, improving the functionality of robots and surgical procedures by providing detailed mechanical information that human touch cannot.
Implementation Method 1
mechanisms and a controller. The analyzer applies the method on the measurements which are taken place by mechanisms and controller enables the mechanisms to perform the deformations and measurements required
Implementation Method 2
nonlinear hyperelasticity and viscoelasticity analyses are applied by the analyzer for characterizing the object and monitoring the results as mechanical properties: nonlinear elastic modulus and dissipation function of energy
Implementation Method 3
These materials include elastic/hyperelastic and/or viscoelastic/plastic materials, which can be classified in two categories as time-independent and time-dependent materials, respectively
Data Source
AI summary
Method and system for real time characterization of soft materials and biological tissues based on nonlinear properties with application in biological tissues diagnostics, robotic assisted surgery, tele-surgery, robotics and minimally invasive surgery is provided.