What Is a Soft Actuator?
An actuator is a device that converts energy into physical motion. While water turbines and windmills can be considered types of actuators, typically actuators imitate the movement of human muscles and joints.
A soft actuator, however, is made from lightweight, flexible materials that respond to environmental changes or external stimuli such as salt, solvents, or heat. These materials enable soft actuators to function similarly to traditional actuators but with added flexibility and responsiveness to external conditions.
Uses of Soft Actuators
Soft actuators are commonly used in artificial muscles due to their light weight and flexibility, making them ideal for robots and heavy machinery. Besides artificial muscles, they are also employed in artificial organs like hearts and anuses.
In industries like construction and nursing care, where workers frequently lift heavy loads, soft actuators are used in lower back support wear and muscle suits to assist movement.
Their sensitivity to external stimuli also opens up possibilities for energy generation in response to temperature changes.
Use of Soft Actuators in Robots
Soft actuators offer advantages such as adaptability, flexibility, light weight, cost-effectiveness, and environmental friendliness. They are stable in air, noise-free, and can passively respond in complex shapes with minimal or no control.
These features make soft actuators particularly useful in robotics, especially for operations in extreme conditions and underwater. For example, next-generation rubber materials in soft actuators can expand and contract when energized, ideal for robotic arms. PVC gel-based soft actuators are used in wearable robots and muscle suits.
Principle of Soft Actuators
Soft actuators operate through various mechanisms based on the materials and activation methods used. For instance, artificial muscles typically function through chemo-mechanical reactions initiated by temperature changes, solvent exchanges, chemical additions, or stimuli like light or electric fields.
A temperature-activated example uses polymethacrylic acid (PMAA), which forms complexes with polyethylene glycol in aqueous solutions. The polymer’s operation relies on the equilibrium between the polymers, shrinking at higher temperatures as polyethylene glycol concentration increases in the solution. This shape memory gel can be reconfigured multiple times using ethanol treatment.
Classification of Soft Actuators
Soft actuators can be categorized based on the materials used:
Polymer Gel Actuators
These actuators utilize polymer gels that deform when voltage is applied. They are known for their responsiveness, light weight, low production cost, and high energy efficiency.
Conductive Polymer Actuators
Made from conductive polymers like polypyrrole (PPY), polythiophene, and polyaniline (PANI), these actuators expand and contract when voltage is applied across electrodes in an electrolytic solution.
Other types include elastomer actuators and carbon nanotube actuators.