Modeling dynamic swelling of polymer-based artificial muscles.

Area of Science:

• Materials Science
• Polymer Science
• Robotics

Background:

• Polymer-based artificial muscles offer lightweight, flexible actuation for specialized applications.
• Achieving desired performance metrics (strain, rate, work) necessitates careful material and geometric design.
• Twisted and coiled polymer (TCP) fibers show promise for significant actuation via radial swelling.

Purpose of the Study:

• To model the actuation of advanced polymers, specifically TCP fibers, for defining design metrics.
• To simulate transient swelling of polymeric networks considering diffusion and ion migration.
• To evaluate the impact of polymer swelling on transport phenomena and quantify work output.

Main Methods:

• Combined analytical thermodynamic modeling (Flory-Rehner Theory) with numerical transport models.
• Simulated transient swelling of polymer fibers, including parametric studies and experimental validation.
• Accounted for local length increases due to solvent presence and modeled anisotropic swelling.

Main Results:

• Increased transport distance prolongs swelling equilibrium time, but voltage application accelerates it via ion migration.
• Sub-second response times, comparable to natural muscles, require dimensions below 100 micrometers.
• Quantified the impact of polymer swelling on transport and the benefits of anisotropic swelling and constant modulus.

Conclusions:

• Modeling polymer swelling is crucial for designing effective artificial muscles.
• Optimizing fiber dimensions and leveraging electrokinetic effects are essential for high-performance TCP artificial muscles.
• This research provides a framework for designing advanced polymer actuators with tailored properties.