Polyacrylonitrile linear actuators: Chemomechanical and electro-chemomechanical properties

Polyacrylonitrile (PAN) fibers were investigated for their use as “artificial muscle” linear actuators. Basic properties and characteristics of PAN fiber gel were investigated using a single strand (yarn) to define the material as an actuator. Properties of interest include force generation, force–strain behavior, and chemical reactions. Diameter and volume changes were observed as greater than 100% and greater than 1000%, respectively for pH activated systems. For the electrically induced systems the diameter and volume changes were similar though the response time was longer. For the elongated state the mechanical properties were not as strong as those in the contracted state, while also having a decreased flexible elasticity. Also, the amount of H+ present affected the shrinking of the fibers as well as the response time, though the effect decreased after the concentration reached a critical value. Profiles of force development for both the pH driven and electrically actuation systems indicate that single PAN strand fibers of a 100 mm length produced an approximate force of 0.1 N for both activation methods. Also, a plot of actuation stress versus actuation strain is constructed to map the current PAN actuator technology against other competing actuator technologies.