Scientists from Taiwan have developed a new material that can stretch up to 4,600% of its original length before breaking. Even if it does break, gently pressing the pieces together at room temperature allows it to heal, fully restoring its shape and stretchability within 10 minutes.
The sticky and stretchy polyurethane (PU) organogels were designed by combining covalently linked cellulose nanocrystals (CNCs) and modified mechanically interlocked molecules (MIMs) that act as artificial molecular muscles.
The muscles make the gel sensitive to external forces such as stretching or heat, where its color changes from orange to blue based on whether the material is at rest or stimulated. Thanks to these unique properties, the gels hold great promise for next-generation technologies—from flexible electronic skins and soft robots to anti-counterfeiting solutions.
The findings are published in Advanced Functional Materials.
MIMs, such as rotaxanes and daisy chains, are promising because their molecular motion enhances toughness and flexibility. MIMs have also opened up the world of mechanochromic materials—substances that fluoresce or change colors in response to a stimulus.
These materials contain molecular switches called mechanophores, which respond to force by breaking and reforming chemical bonds, leading to small but dramatic structural shifts.
Studies show that even small amounts of MIMs can greatly enhance the stretchability and toughness of polymers. While mechanophores are commonly used for temperature and force sensing, incorporating them into self-healing systems has proven challenging.
To address this, the researchers experimented with a range of compositions to develop novel PU organogels. They achieved their desired strength, stretch, self-repair, adhesion, and color-changing properties in organogels by incorporating MIMs modified with special fluorescent groups called DPAC and cellulose nanocrystals via a step-growth polymerization process.
The PU organogels containing about 1.5 wt.% MIMs exhibited excellent toughness of 142 MJ/m3 and stretchability 46 times its own size. The organogels emitted orange or blue fluorescence depending on how stretched the material was.
When relaxed, DPAC units in the material vibrated in an unconstricted way with a frequency of 603 nm, resulting in orange light. Stretching applied force that drove the DPAC units to slide, constraining the vibrations and shifting the emission to blue at 451 nm.
The gels autonomously self-healed at room temperature, recovering more than 90% of their original strength and stretchability. This self-repair was supported by hydrogen bonding introduced through cellulose nanocrystals.
Scaled for mass production, this material could enable sustainable technologies by signaling repairs and extending product lifetimes.
Written for you by our author Sanjukta Mondal, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
More information: Tu Thi Kim Cuc et al, Effective Sliding Motions of Vibration‐Induced Emission Stoppers in Mechanically Interlocked Molecules as Artificial Muscle Tougheners and In Situ Molecular Shuttling Sensors for Self‐Healable Mechano‐Fluorescent Polyurethane Organogels, Advanced Functional Materials (2025). DOI: 10.1002/adfm.202519737
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Citation: Color-changing organogel stretches 46 times its size and self-heals (2025, September 17) retrieved 24 October 2025 from https://phys.org/news/2025-09-organogel-size.html
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