Drive soft robots: agile and strong

Compared to conventional rigid robots with heavy metals and tethered motors, soft robots, made of soft materials, demonstrate promising work, like the intelligent biological organisms, because they have a greater degree of freedom, to be nimble and adapt to environmental changes. However, their softness can also be problematic, when it comes to complex forms or strains of hard work.

For precise control and local forms and soft robots movement with considerable force and deformation required actuators, who are very responsive and durable.

Among the various soft and sensitive materials liquid crystal elastomers (LCE) demonstrate the intrinsic anisotropy and reversible deformation of the shape during phase transitions under the influence of external stimuli, including heat and light, which is very desirable for actuators. By controlling molecular alignment of liquid crystal molecules within the network, You can program the movement of LCE. However, spatial equalization control usually requires multistage manufacture and limits the size of actuators. As elastomers, most LCE actuators also lacks the desired mechanical strength to create a large volume of work.

Inspired by the musculoskeletal system in humans and other animals, Our team, led by Shu Yang professor at the University of Pennsylvania has recently developed based on the extrusion method for the manufacture of incandescent drives LCE meter.

To improve the mechanical strength of the yarn is added to elastomers 2 wt.% of carbon nanotubes, are known for their ultra-high strength, low mass and high electrical and thermal conductivity. Besides, a small amount of cellulose nanocrystals, a unique type of nanomaterial, obtained from plant cellulose fibers, It was mixed to improve the alignment of liquid crystal molecules inside thread, which is essential for achieving anisotropic mechanical and reversible reactions.

The ability of carbon nanotubes to absorb near infrared light and generate heat can cause a phase transition in the LCE, that triggers the filament in the light. By combining copper wires with a thread, passing an electric current for heating, hybrid yarn LCE is also sensitive electrothermal.

Consequently, Filament drive has a double sensitivity and can be quickly and reversibly actuated by applying a near-infrared light, a small voltage (8 AT), as shown below.

Schematic representation of activations, respond to near-infrared light (left panel) and electrothermal reactions (right panel), using liquid crystalline elastomer yarns, doped carbon nanotubes.

The thread can be placed in arbitrary structure or integrated into a system-level robotics for any type of movement. Maximum performance (the ability of the actuators to perform mechanical work) is 38 Joules per kilogram – value, comparable with the value of the skeletal muscles in mammals.

"Our hybrid design of the LCE thread allows soft robots lift heavy objects, without diminishing their agility. force, created during actuation, It is one of the highest values ​​in the current soft actuators ", – Gao said Yuchong, lead author of the article. "The muscular form of thread, providing an even greater degree of freedom than the traditional film drives, It is also ideally suited for integration into various types of soft intelligent robotic systems ".

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