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A coupled theory accounting for fluid diffusion and large deformations of elastic-viscoplastic microporous polymeric materials is presented. The theory is intended to represent the coupled deformation–diffusion response of a material which at a microscopic scale consists of a porous polymeric skeleton and a freely moving fluid in a fully connected pore space. Potential applications of the theory include modeling the response of polymer microfiltration membranes, as well as modeling the response of several hydrated biological tissues which are microporous polymeric materials containing a high concentration of liquids. [ABSTRACT FROM AUTHOR]

• Analytical model for the drug delivery time considering flexural, fluidic, and geometrical parameters in injectable microsystems. • Design and optimization guidelines using concise non-dimensional formulae for injectable microsystems. • Concise analytical, but parametric, formulae to determine the pressure-volume relationship of any flexible polymer membrane using the Marlow hyper-elastic model. Injectable bioelectronic devices provide programmable drug volume delivery control via flexible electrochemical pumps featuring scalable designs for localized drug delivery experiments involving small animals and future drug delivery in humans, especially for life saving medication. A model for the drug delivery time is established from the ideal gas law, finite-deformation theory of flexible membrane, and microfluidics of the channel. It identifies two non-dimensional parameters involving the electrochemical, flexural, and microfluidic terms to control the drug delivery process. An analytical solution is derived from the perturbation method, which agrees well with the numerical solution. These results have relevance in design/optimization of bioelectronic devices used in localized delivery studies in small animals and humans where drug delivery time is an important parameter to ensure complete delivery within a required timeframe. [ABSTRACT FROM AUTHOR]

Ionic polymer metal composites (IPMCs) consist of an electroactive polymeric membrane plated with metal electrodes. They hold promise as actuators and sensors for soft robotics and biomedical applications. Their capabilities ensue from the motion, within the membrane, of a fluid phase consisting of ions dispersed in a solvent. Toward a thorough understanding of IPMC multiphysics, we propose a large deformation theory combining electrochemistry and poromechanics. Namely, we modify the theory recently developed by Porfiri's group by introducing the transport of the solvent, whose redistribution determines the volumetric deformation of the fluid-saturated membrane, and we further account for the cross-diffusion of solvent and ions. In actuation, the imposed voltage drop across the electrodes triggers ion migration, such that the solvent is transported toward the cathode by electro-osmosis. This determines the initial bending toward the anode; then, back-relaxation occurs because of both the solvent counter-diffusion and the asymmetric redistribution of ions near the electrodes. In short-circuit sensing, the applied load triggers solvent motion, such that ions are mainly transported toward the cathode by convection with the solvent. This determines charge accumulation; then, ion counter-diffusion leads to a decrease of the charge stored at the electrodes. We demonstrate that these behaviors can be predicted by the proposed theory on the basis of relevant finite element benchmarks. Additionally, our analysis encompasses the assessment of the role of the membrane elastic moduli in the counter-diffusion of solvent and ions in IPMC actuation and sensing. • New electrochemo-poromechanical theory for ionic polymer metal composites (IPMCs). • Finite deformation theory including the cross-diffusion of solvent and mobile ions. • Prediction of counter-diffusions of solvent in actuation and ions in sensing. • Explanation of back-relaxation through both electrostatics and solvent transport. • Assessment of the role of the membrane elastic moduli on IPMC actuation and sensing. [ABSTRACT FROM AUTHOR]