Electrochemomechanical Behavior of Polypyrrole-Coated Nanofiber Scaffolds in Cell Culture Medium.

Glucose-gelatin nanofiber scaffolds were made conductive and electroactive by chemical (conductive fiber scaffolds, CFS) and additionally electrochemical polypyrrole deposition (doped with triflouromethanesulfonate CF3SO3-, CFS-PPyTF). Both materials were investigated in their linear actuation properties in cell culture medium (CCM), as they could be potential electro-mechanically activated cell growth substrates. Independent of the deposition conditions, both materials showed relatively stable cation-driven actuation in CCM, based on the flux of mainly Na+ ions from CCM. The surprising result was attributed to re-doping by sulfate anions in CCM, as also indicated by energy-dispersive X-ray (EDX) spectroscopy results. Overall, the electrochemically coated material outperformed the one with just chemical coating in conductivity, charge density and actuation response.

Comparative Analysis of Fluorinated Anions for Polypyrrole Linear Actuator Electrolytes.

Either as salts or room temperature ionic liquids, fluorinated anion-based electrolytes have been a common choice for ionic electroactive polymer actuators, both linear and bending. In the present work, propylene carbonate solutions of four electrolytes of the three hugely popular anions-triflouromethanesulfonate, bis(trifluoromethane)sulfonimide, and hexafluorophosphate were compared and evaluated in polypyrrole linear actuators. The actuation direction, the characteristics-performance relations influence the behavior of the actuators. Isotonic Electro-chemo-mechanical deformation (ECMD) measurements were performed to study the response of the PPy/DBS samples. The highest strain for pristine PPy/DBS linear actuators was found in range of 21% for LiTFSI, while TBAPF6 had the least cation involvement, suggesting the potential for application in durable and controllable actuators. Interesting cation effects on the actuation of the same anions (CF3SO3-) were also observed.

Low concentrated carbonaceous suspensions assisted with carboxymethyl cellulose as electrode for electrochemical flow capacitor.

The search for efficient energy storage devices has recently led to the introduction of a fluid electrode material employing electrochemical flow capacitors (EFC). Unlike the classical solid electrode film containing capacitors, where the electrode material is fixed to the current collectors and capacitance is therefore limited with an active surface area of porous electrode, the flow electrodes offer new design opportunities which enable fully continuous charging/discharging processes as well as easily scalable systems. Here we describe the successful incorporation of the carboxymethyl cellulose sodium salt (CMC-Na) assisted carbonaceous suspension electrode in aqueous media for the electrochemical flow capacitor concept and demonstrate the electrochemical charge storage in flowable electrodes using a cation conductive membrane as separator in a double-pipe flow-electrode module. Experimental results were combined with computer simulations (FEM) to specify limiting processes EFC charging. The flow-electrode slurry is based on 0.1 M Na2SO4, 3 wt% CMC-Na and activated carbon powder suspended in water. During continuous operation of the system, the capacitance of the flow electrode reached to 0.3 F/L providing the energy and current densities of 7 mWh/kg and 56 mW/L, respectively. Additionally, we report a 70% round trip efficiency calculated during charging and discharging of the cell between 0 V and +0.75 V, while applying the current density of 1.6 mA/kg. The double-pipe flow-electrode module is easily expandable for transportation of large volumes of electrode material.

Natural cellulose ionogels for soft artificial muscles.

Rapid development of soft micromanipulation techniques for human friendly electronics has raised the demand for the devices to be able to carry out mechanical work on a micro- and macroscale. The natural cellulose-based ionogels (CEL-iGEL) hold a great potential for soft artificial muscle application, due to its flexibility, low driving voltage and biocompatibility. The CEL-iGEL composites undergo reversible bending already at ±500mV step-voltage values. A fast response to the voltage applied and high ionic conductivity of membranous actuator is achieved by a complete dissolution of cellulose in 1-ethyl-3-methylimidazolium acetate [EMIm][OAc]. The CEL-iGEL supported cellulose actuator films were cast out of cellulose-[EMIm][OAc] solution via phase inversion in H2O. The facile preparation method ensured uniform morphology along the layers and stand for the high ionic-liquid loading in a porous cellulose scaffold. During the electromechanical characterization, the CEL-iGEL actuators showed exponential dependence to the voltage applied with the max strain difference values reaching up to 0.6% at 2 V. Electrochemical analysis confirmed the good stability of CEL-iGEL actuators and determined the safe working voltage value to be below 2.5V. To predict and estimate the deformation for various step input voltages, a mathematical model was proposed.

Ionic electroactive polymer artificial muscles in space applications.

A large-scale effort was carried out to test the performance of seven types of ionic electroactive polymer (IEAP) actuators in space-hazardous environmental factors in laboratory conditions. The results substantiate that the IEAP materials are tolerant to long-term freezing and vacuum environments as well as ionizing Gamma-, X-ray, and UV radiation at the levels corresponding to low Earth orbit (LEO) conditions. The main aim of this material behaviour investigation is to understand and predict device service time for prolonged exposure to space environment.

Microporous and mesoporous carbide-derived carbons for strain modification of electromechanical actuators.

Low-voltage stimuli-responsive actuators based on carbide-derived carbon (CDC) porous structures were demonstrated. Bending actuators showed a differential electromechanical response defined by the porosity of the CDC used in the electrode layer. Highly porous CDCs prepared from TiC (mainly microporous), B4C (micromesoporous), and Mo2C (mainly mesoporous) precursors were selected to demonstrate the influence of porosity parameters on the electromechanical performance of actuators. CDC-based bending-type actuators showed a porosity-driven displacement response over a frequency range of 200 to 0.005 Hz at an applied excitation voltage of ±2 V. The displacement response of the CDC actuators increased with an increasing number of mesopores in the electrode layer, and the generated strain of the bending actuators was proportional to the total porosity (micropores and mesopores) of the CDC. The modifiable electromechanical response that arises from the precise porosity control attained through tailoring the CDC architecture demonstrates that these actuators hold great promise for smart, low-voltage-driven actuation devices.