An ultrathin, ‘artificial muscle’ for soft robotics

In recent years, soft robotics has gained increasing attention due to their advantages like high flexibility and safety for human operators. However, its fabrication is still a challenge. As if you built a soft, flexible robot but then put rigid, unyielding actuators inside of it, you are kind of defeating the whole purpose of the thing.

So to overcome this problem, a team of KAIST researchers has developed very thin, responsive, flexible and durable artificial muscles for soft robotics. These actuators look like a skinny strip of paper about an inch long. These are made of a type of material called MXene, which is a class of compounds that have layers only a few atoms thick.

Initially, when MXene material (T3C2Tx) was applied to one side of a thin strip of a flexible polymer, it caused that strip to bend when an electrical current was applied. But because the MXene itself is not very flexible, bits of it flaked off of the polymer every time it bent.

This was changed, when the team “ionically cross-linked” the MXene to a synthetic polymer. It made the actuator flexible, while still maintaining strength and conductivity, which is critical for movements driven by electricity.

The strips made of the resulting material bend quickly in response to even relatively low voltage, and lasted for more than five hours moving continuously.

The researchers have demonstrated the artificial muscle in the form of a narcissus-flower-like brooch that opens its petals when a small amount of electricity is applied and in robotic butterflies that move their wings up and down.