Soft actuator could be ‘holy grail’ for soft robotics
Soft robots do a lot of things well but they’re not exactly known for their speed. The artificial muscles that move soft robots, called actuators, tend to rely on hydraulics or pneumatics, which are slow to respond and difficult to store.
Dielectric elastomers, soft materials that have good insulating properties, could offer an alternative to pneumatic actuators but they currently require complex and inefficient circuitry to deliver high voltage as well as rigid components to maintain their form— both of which defeat the purpose of a soft robot.
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a dielectric elastomer with a broad range of motion that requires relatively low voltage and no rigid components.
They published their work recently in Advanced Materials.
“We think this has the potential to be the holy grail of soft robotics,” said Mishu Duduta, a graduate student at SEAS and first author of the paper. “Electricity is easy to store and deliver but until now, the electric fields required to power actuators in soft robots has been too high. This research solves a lot of the challenges in soft actuation by reducing actuation voltage and increasing energy density, while eliminating rigid components.”
Lightweight suit to increase the wearer’s strength and endurance
For decades engineers have built exoskeletons that use rigid links in parallel with the biological anatomy to increase the wearer’s strength and endurance, and to protect them from injury and physical stress. In recent years, a number of systems have been developed that show strong commercial potential for helping spinal-cord injury patients walk, or helping soldiers carry heavy loads. In these systems, there is an exoskeleton structure in parallel with the wearer’s skeletal structure that is typically connected at a few locations on the body using straps or belts. These devices use motors or elastic materials to assist with joint movements, thereby enhancing human power. However, exoskeletons often fail to allow the wearer to perform his or her natural joint movements, are generally heavy, and can hence cause fatigue.
The Wyss Solution
Targeting a specific set of applications where a wearer needs some partial assistance from a robot, Wyss Institute researchers are pursuing a new paradigm: the use of soft clothing-like “exosuits.” An exosuit does not contain any rigid elements, so the wearer’s bone structure must sustain all the compressive forces normally encountered by the body — plus the forces generated by the exosuit. The suit, which is composed primarily of specially designed fabrics, can be significantly lighter than an exoskeleton since it does not contain a rigid structure. It also provides minimal restrictions to the wearer’s motions, avoiding problems relating to joint misalignment.
Exosuits exemplify a new class of applications for soft robotics, an emerging field that combines classical robotic design and control principles with active soft materials.