Improving the the Actuation of Polymeric Artificial Muscles Using Magnetically Aligned Polyelectrolytes

Electroactive polymers comprise an emerging class of electromechanical actuators materials that can be used as biomimetic sensors and actuators in wide range of applications from medical devices to robotics applications. Among this class of smart materials, ionic polymer-metal composites (IPMCs) are considered most suitable for artificial muscles since they exhibit a large their large bending motion under relatively low input voltage, flexibility, biocompatibility, and lightweight properties. The polyelectrolytes membrane is a key part of the state-of-the art IPMC devices which act as an ion exchange media to support ionic transport and as a result bending motion of these structures. A recent morphological study of polyelectrolytes confirms the presence of hydrophilic ionic nanochannels that are randomly distributed laterally. These nanochannels are key players to tune the transport properties.

In the current research, we made Nafion/ Imidazole-functionalized superparamagnetic iron oxide nanoparticles (SPIONs) nanocomposite membranes and then by applying external magnetic field we made an induced alignment normal to the membrane’s surface. The effects of the anisotropic dispersion (alignment) of these nanoparticles on phase separation and ionic (H⁺, Li⁺, and Na⁺) conductivity of resulted membranes studied using small angle X-ray scattering (SAXS) and electrochemical impedance spectroscopy (EIS), respectively. Membranes with aligned nanodomains demonstrate higher bending forces as well as faster bending response (tip displacement rate). Due to formation of strong electrostatic interactions between sulfonated groups of Nafion and Imidazole groups at the SPION’s surface these structures display good performance in low humidity conditions as well. Results converge to indicate the effective presence of aligned nanoparticles especially in their functionalized state to tune performance of ionic polymer metal composite. This class of actuators can be applied for wide range of applications with different humidity conditions.