The document summarizes simulation work on modeling the micro-actuation of pH and electric field sensitive hydrogels. It presents the governing equations used in the modeling, including the Nernst-Planck equation, Poisson's equation, and mechanical field equations. It describes the finite element method formulation and simulation setup in COMSOL, including applying different fixed charge densities and electric potentials to the hydrogel. The results show concentration profiles, electric potential distributions, and deformation of the hydrogel matching other numerical and experimental results. Future work is planned to model transient behavior.

1. Simulation of Hydrogel Micro-actuation Presented by Kamlesh Suthar* Authors Dr. M. Ghantasala* Dr. D. Mancini # *Department of Mechanical and Aeronautical Engineering, Western Michigan University, Kalamazoo, MI USA - 49008 # Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL, USA – 60439

4. Research Goal Electric Field sensitive pH sensitive

6. Governing Eqution Nernst-Planck Equation: Continuity equation Poisson’s Equation : Mechanical Field Equation : Diffusion co-efficient of ith ion Concentration of ith ion Valence of ith ion Faraday constant Universal gas constant Temperature Electric field potential Mobility of ith Ion Fixed ion concentration Hydration Strain Induced stress Material elasticity matrix Osmotic Pressure

7. Algorithm

11. Results : No external Electric Potential Buffer ion inside the gel Electric Potential In the gel

12. Results: Concentration Profiles at Different Applied Voltages Buffer ion concentration profile at different applied potential for a fixed charge concentration of 4mM

13. Results: Deformation

15. Future Work, Solving Transient problem

17. Thank You