Biomimetic Double-Network Hydrogels for Reversible Stiffness
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Solution Overview
Problem
Existing hydrogels lack the ability to tune mechanical properties reversibly with external stimuli and achieve high stiffness at low temperatures, limiting their applicability in biomedical and tissue engineering applications.
Innovation Solution
A double network hydrogel system comprising a semi-flexible polymer with a persistence length between 10 and 1000 nm and a flexible polymer with a persistence length smaller than 1 nm, where the flexible polymer undergoes a conformational change with temperature, is crosslinked with a specific crosslinker, and combined with a semi-flexible polymer to create a strain-stiffening double-network hydrogel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-component hydrogel is used, then the structure is simple and easy to manufacture, but the mechanical strength and toughness are insufficient
Solution Approach 1:
The patent employs a double-network hydrogel composite structure consisting of a first network formed by semi-flexible polymers (e.g., polyisocyanopeptides, fibrin, actin) and a second network formed by flexible polymers (e.g., polyacrylamide, PEG, PNIPAM). This composite architecture combines the strain-stiffening properties of semi-flexible networks with the toughness and reversible mechanical responses of flexible networks, achieving superior mechanical strength and functional responsiveness that neither single network could provide alone.
2Strength
If flexible polymers with persistence length smaller than 1 nm are used, then the hydrogel is easy to manufacture, but the mechanical strength is insufficient
Solution Approach 1:
The patent merges two distinct polymer networks with complementary properties: semi-flexible polymers (persistence length 10-1000 nm) that provide structural integrity and strain-stiffening, and flexible polymers (persistence length <1 nm) that contribute toughness and reversible mechanical behavior. The synergistic combination of these merged networks achieves high mechanical strength while maintaining ease of manufacture through established hydrogel fabrication techniques.
3Adaptability or versatility
If thermoresponsive polymers are incorporated, then the mechanical properties can be tuned reversibly, but the device complexity increases
Solution Approach 1:
The patent utilizes parameter changes in polymer conformation in response to temperature variations. Thermoresponsive polymers (e.g., PNIPAM, polyacrylamide) undergo coil-to-globule transitions at specific temperatures, causing reversible changes in network stiffness and mechanical properties. This allows dynamic tuning of the hydrogel's mechanical behavior without fundamental system redesign, achieving adaptability through controlled physical parameter changes rather than structural 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 high mechanical strength and reversible mechanical properties by combining the thermal response of the flexible polymer with the strain-stiffening effect of the semi-flexible polymer, allowing for tunable stiffness and robust structural changes in response to temperature.
Implementation Method 1
polymer (B) has an extended coil conformation at a first condition and a collapsed globular conformation at a second condition
Implementation Method 2
polymer (A) is a oligo(alkylene glycol)functionalized poly(isocyanopeptide) wherein the polyisocyanide hydrogels show reversible mechanical properties as a function of the temperature
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a double network hydrogel comprising a polymer (A) having a persistence length between 10 and 1000 nm; a flexible polymer (B), wherein the persistence length is measured according to single molecule force microscopy measurement, wherein polymer (B) has an extended coil conformation at a first condition and a collapsed globular conformation at a second condition. Polymer (A) preferably is a polyisocyanate, while polymer (B) is a crosslinked flexible polymer like for example PNIPAM. The invention also relates to a method for making a double network hydrogel.