AI News, A Super-Stretchy Self-Healing Artificial Muscle

A Super-Stretchy Self-Healing Artificial Muscle

When you pull a muscle, it may hurt like heck for a while, but the human body can heal.

This version of the material is not going to power a robot to win any weight-lifiting contests: it generates just a small amount of force, expanding by 3.6percent under an electric field of 17.2 millivolts per meter.

(The muscle expands in one dimension, contracting in the other two.) Artificial muscles contract in response to an electric field, similar to biological muscles, but they’re typically made of polymers.

Bao is known for developing more sensitive, more life-like electronic skin for robotics and prosthetics, and the new chemical design basics will help make better materials for those efforts.

The idea behind the project is not to create the world’s strongest artificial muscle, says Bao, but to learn how to engineer polymers with totally new combinations of properties—in this case, very stretchy self-healing material that’s electrically responsive.

It’s so stretchy that the mechanical-testing equipment on hand in the lab was not big enough to pull it as far as it would go—two students had to tug the material across the room.

Right now she’s working on creating stretchy self-healing polymers with the right electronic properties to make the different parts of a full transistor—semiconductors, conductors, and dielectric materials.

A super stretchy, self-healing material could lead to artificial muscle

If there's such a thing as an experiment that goes too well, a recent effort in the lab of Stanford chemical engineering Professor Zhenan Bao might fit the bill.

To find the breaking point of their one-inch sample, Li and another lab member had to hold opposing ends in their hands, standing further and further apart, eventually stretching a 1-inch polymer film to more than 100 inches.

Damaged polymers typically require a solvent or heat treatment to restore their properties, but the new material showed a remarkable ability to heal itself at room temperature, even if the damaged pieces are aged for days.

The team attributes the extreme stretching and self-healing ability of their new material to some critical improvements to a type of chemical bonding process known as crosslinking.

This process, which involves connecting linear chains of linked molecules in a sort of fishnet pattern, has previously yielded a tenfold stretch in polymers.

The version that exceeded the measuring machine's limits, for example, was created by decreasing the ratio of iron atoms to the polymers and organic molecules in the material.

(View video.) In addition to its long-term potential for use as artificial muscle, this research dovetails with Bao's efforts to create artificial skin that might be used to restore some sensory capabilities to people with prosthetic limbs.

Even before artificial muscle and artificial skin become practical, this work in the development of strong, flexible, electronically active polymers could spawn a new generation of wearable electronics, or medical implants that would last a long time without being repaired or replaced.

This latest discovery is the result of two years of collaboration, overseen by Bao, involving visiting scholar Cheng-Hui Li, a Chinese organo-metallic chemist who designed the metal ligand bonding scheme;

Anyone who has ever smashed their iPhone's screen or depleted a battery knows that devices are destined to deteriorate and eventually die.

That's the vision Chao Wang, a polymer researcher and assistant professor in the chemistry department at the University of California, Riverside has for the future — and he helped invent a super-stretchy, self-healing polymer that could one day make it possible.

Polymers that mend themselves using microcapsules filled with healing agents already exist, points out Wang, but once those microcapsules are punctured, more repairs can't be performed — and the material can't stretch to its limits again.

To achieve a substance that could heal itself again and again, Wang and his colleagues relied on crosslinking, a chemical process that links long and short chains of molecules together in a kind of fishnet pattern.

The polymer could have less obvious applications: for example, the sound quality of present-day headphones is dictated by electromagnetism, but self-healing polymer that conducts electricity could replace that mechanism to provide more subtle, vivid sound variations as it stretches and reforms.

He admits that it may take a while for the idea of polymers that stretch, bend, and all but breathe to catch on in consumer electronics, but thinks that once an initial market is demonstrated, the idea will catch on.

KurzweilAI | Accelerating Intelligence.

Stanford researchers have developed a new material that can stretch to 100 times its original length by exposing it to an electric field, and even repair itself if punctured, making it potentially useful as an artificial muscle.

Artificial muscles currently have applications in some consumer technology and robotics, but small holes or defects in the materials currently used make them less resilient, and they can’t self-repair if punctured or scratched, according to Stanford chemical engineering professor Zhenan Bao.

Damaged polymers typically require a solvent or heat treatment to restore their properties, but the new material can heal itself at room temperature (even if the damaged pieces are aged for days) and at temperatures as low as negative 4 degrees Fahrenheit (-20 C).

The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl–iron one, and two weaker carboxamido–iron ones through both the nitrogen and oxygen atoms of the carboxamide groups.

As a result, the iron–ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains.

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