A newly invented self-adaptive material can heal itself and recover from extreme compression, serving as a potentially useful tool for tissue engineering or the creation of lightweight, defect-proof structural components.

The material called self-adaptive composite or SAC – born out of Rice University in Texas and presented in the journal ACS Applied Materials and Interfaces of the American Chemical Society – combines self-healing and reversible self-stiffening components.

SAC is made up of sticky and micron-scale rubber balls forming a solid matrix. It was produced through a combination of two polymers and a solvent evaporating when heated – a mix that creates a porous mass of gooey spheres.

The matrix heals quickly even when cracked repeatedly and returns to its initial form after being compressed, much like the usual sponge.

Self-Healing Material Goes A Notch Higher

Other self-healing materials today enclose liquid in solid shells that leak their healing properties when cracked. The Rice researchers thus focused on one crucial aspect: greater flexibility.

“We wanted a biomimetic material that could change itself, or its inner structure, to adapt to external stimulation and thought introducing more liquid would be a way,” explained postdoctoral researcher and co-study lead author Pei Dong in a press release, also emphasizing their goal for the liquid to stay stable rather than flow everywhere.

In SAC, here is how it works: tiny polyvinylidene fluoride (PVDF) spheres enclose much of the liquid, while the entire surface is further covered by viscous polydimethylsiloxane (PDMS).

Rice University materials scientist Jun Lou noted that the spheres are highly resilient given that their thin shells easily deform. Their liquid content, too, improves their capacity to absorb the strain and revert to their original form.

The coatings keep the intact quality of the spheres, which also freely slide past each other during compression without breaking apart.

Lou touted that the sample does not reveal the fact that it is filled with liquid. “This is not really squishy; it’s more like a sugar cube that you can compress quite a lot,” he said, highlighting SAC’s ability to recover.

Unlike gels that have a lot of liquid and way too soft, SAC boasts of mechanical power, resulting in an “extreme gel” where the liquid stage is only about half or so, Lou added.

The process of creating SAC can also be modified to be a bit more solid or a bit more liquid, adjusting the product’s mechanical quality.

The researchers are currently creating the material, which are limited only by their container, in a 150-milliliter beaker, but production can be scaled up for more industrial purposes.

The Promise Of Tissue Engineering

The self-adaptive material is poised to be a useful addition to the thriving sector of tissue engineering, which aims to address tissue and organ failure, a major health concern in the United States.

Treatment options include surgical repair, transplantation, mechanical devices, artificial prostheses, and sometimes drug therapy – all of which may not repair or restore major tissue or organ damage. Tissue engineering is hoped to serve as an alternative or complementary fix here, implanting fully functional natural or synthetic tissue and organ mimics.

This scientific endeavor – which has resulted so far in tissue-engineered bone, blood vessels, muscle, liver, and nerve conduits – involves engineering tissue types and using biomaterials for delivery.

“As a result of the medical and market potential, there is significant academic and corporate interest in this technology,” wrote researchers in a study published in the journal Nature Biotechnology.


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