A team of Harvard University’s experts in mechanics, materials science and tissue engineering created an extremely tough and stretchy gel that may be used to replace human cartilage in joints.

The main ingredient of the hydrogel is water and is a hybrid of two weaker gels that combine to form something much stronger.  Its properties of being tough, self-healing and biocompatible open new doors in the fields of medicine and tissue engineering.

“Conventional hydrogels are very weak and brittle—imagine a spoon breaking through jelly,” explains Jeong-Yun Sun, lead author of the study and a postdoctoral fellow at the Harvard School of Engineering Applied Sciences. 

“But because (hydrogels) are water-based and biocompatible, people would like to use them for some very challenging applications like artificial cartilage or spinal disks.  For a gel to work in those settings, it has to be able to stretch and expand under compression and tension without breaking.”

Image on left shows a 2-centimeter notch researchers cut across the gel.  The image on right shows the damaged gel stretched 17 times its original length without breaking  (A rubber band stretches only 6 times its length before breaking.)   Photo credit Jeong-Yun Sun.

The two elements researchers combined to create the new hydrogel are both polymers.  The primary component is polyacrylamide, used in soft contact lenses.  The second polymer is alginate, a seaweed extract used to thicken foods.

Harvard faculty member, Zhigang Suo, observed, “The unusually high stretchability and toughness of this gel, along with recovery, are exciting.  Now that we’ve demonstrated that this is possible, we can use it as a model system for studying the mechanics of hydrogels further, and explore various applications.   It’s very promising.”

Researchers suggest the new hydrogel could also be used in soft robotics, optics, artificial muscle, as a tough protective covering for wounds or “any other place where we need hydrogels of high stretchability and toughness.”

Sources:   Harvard EDU, September 5, 2012      SmartPlanet, September 11, 2012       Study published in Nature, September 6, 2012

Study funded by US Army Research Office, the National Science Foundation (NSF), the Defense Advanced Research Projects Agency, the National Institutes of Health and the NSF-funded Materials Research Science and Engineering Center at Harvard.



  1. I recently learned I have some permanently ruptured tendons! I hope this research might provide me with a solution some day soon! Thanks for reporting on this development! Very promising!

  2. I’m saddened to hear about your thoroughly ruptured tendons. Every tendon in your artist’s body is involved with your ability to continue your career, and I do hope you’ll acquaint your doctor with the hydrogel in the pipeline.

    Hugs, Carole

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