Injectable Gel Flexibility via Viscoelastic Crossover
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Solution Overview
Problem
Current methods for characterizing the mechanical properties of injectable gels, such as dermal fillers, are inadequate as they rely solely on elastic modulus and do not effectively account for the gel's behavior after injection, particularly in terms of flexibility and natural animation.
Innovation Solution
A process involving oscillating mechanical stresses to determine the crossover point between elastic and viscous moduli, providing a comprehensive measure of flexibility that accounts for both elastic and viscous deformations, allowing for a more accurate assessment of a gel's suitability for injection and movement compatibility with facial tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only elastic modulus is used to characterize gel mechanical properties, then the characterization is simple, but it does not account for viscous deformation and flexibility
Solution Approach 1:
The patent combines both elastic modulus (G') and viscous modulus (G'') measurements into a single flexibility parameter. The flexibility is defined as the ratio G''/G' which integrates both elastic and viscous properties, providing a comprehensive characterization that resolves the limitation of using only elastic modulus while maintaining measurement simplicity through a unified parameter.
2Reliability
If elastic modulus alone is measured, then the measurement process is simple, but it cannot predict gel behavior after injection and movement compatibility
Solution Approach 1:
The patent introduces a new parameter (flexibility ratio G''/G') that changes based on the gel's viscoelastic properties. This parameter transformation allows the characterization to capture both elastic and viscous behaviors, enabling better prediction of gel performance after injection and during facial movements, thereby improving reliability without sacrificing measurement precision.
3Measurement precision
If a comprehensive measure of flexibility is obtained by considering both elastic and viscous moduli, then the characterization accuracy is improved, but the measurement and calculation complexity increases
Solution Approach 1:
The patent extracts the essential flexibility information by taking out only the critical ratio between viscous and elastic moduli (G''/G'). Instead of requiring complex integration of the entire modulus curves as in prior art, the method identifies and uses this single extracted parameter, which simplifies the measurement and calculation process while maintaining comprehensive flexibility characterization.
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
This method enables a more precise characterization of injectable gels by measuring flexibility, ensuring they can naturally follow facial movements and maintain natural expressions, thereby improving the evaluation of dermal fillers containing cross-linked hyaluronic acid.
Implementation Method 1
A sample gel is subjected to oscillating mechanical stresses to determine the elastic modulus G' and a score is derived from the integration of G'
Data Source
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AI summary
The present invention provides a process for evaluating rheological characteristics of an injectable gel comprising measuring the flexibility, wherein the flexibility is evaluated by measuring the strain at the crossover point of the amplitude sweep. As an example, the process may comprise subjecting an injectable gel to oscillating mechanical stresses to determine G' and G" as a function of strain (γ) in an amplitude sweep, determining the crossover point as the point at which G' and G" have the same value, determining the strain Ycrass at the crossover point, and determining the flexibility of the injectable gel as Ycrass or proportional to Ycross. The present invention further provides a method of comparison of dermal fillers by measuring their flexibility and a method of evaluation of dermal filler behavior in human skin by measuring the flexibility according to the previous claims.