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Soft Actuators Overview

Soft Actuators Overview

Consider for a moment your arm, a simple action, say, lifting a cold drink from a table on a hot summer’s day. Your bicep contracts as your tricep relaxes so that the drink is lifted from the table toward your mouth. And when you’re done, the process reverses: tricep contracts, bicep relaxes, and voila, the drink is back where it started. Not a process we intentionally think about very often . . . until something goes awry.

For someone who has suffered, for example, impairment from a stroke, such actions may not be so simple, or how about for those who need prosthetic limbs? A subsection of the robotics field is grappling with a potential paradigm-shifting technology that could provide affordable and efficient solutions in such situations.

Soft actuators are devices that employ soft, pliable materials that can be stimulated by various means such as electricity, chemical triggers, light, heat, or pH to create motion. But why bother? To answer this question, consider that simple motion we began with. To reproduce that lifting motion for someone who needs a robotic prosthetic arm, reciprocal systems have to be in place to create the counteracting forces of contraction and extension. Traditional actuators are constructed of steel and would have to be manufactured to individual arm lengths. Weight becomes a factor in producing an actuator that produces sufficient force, as does the price of producing the components.

Soft actuators offer an easier-to-produce, cost-efficient, lightweight alternative with a high power-to-weight ratio. In one experiment, a soft specialized actuator utilized heat to cause expansion of the material. When encased, the expanded material acted like a contracting muscle. Because they are lightweight, affordable, and easily customizable, such units would make the fabrication of body-specific arms much cheaper and quicker.

Such devices are already being tested on stroke patients who have limited hand function and on heart patients. Traditional heart replacement has required a device with which the blood comes into contact, which has caused complications such as thromboembolism, infections, and allergic reactions. With a soft actuator heart replacement, the device essentially fits the outside of an existing heart, assisting it in its complex contractions and relaxations without coming into direct contact with the blood.

Soft actuation is still in its early stages, but it offers great promise in the field of prosthetics. Its resistance to damage and greater compatibility between robotic function and human tissue predict a future of prosthetics that will operate and appear more lifelike.


Ivan Young is a writer with Happy Writers, Co. in partnership with wrought iron door manufacturer Abby Iron Doors.

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