Ionomeric Polymer-metal Composite Research Articles

Nafion-based ionomeric polymer/metal composites operating in the air: theoretical and electrochemical analysis

Nafion/Pt-based ionic polymer metal composites can be considered smart materials with characteristics that allow it to be used as soft actuators. Its working mechanism is based on solvated counterions moving through hydrophilic sites of the polymer membrane, making it an electrochemical device. Since a minimum of 2 V is needed to actuate, water electrolysis is a drawback that must be overcome, once its occurrence inhibits the properly working of ionomeric polymer/metal composite (IPMC). With individually four distinct counterions incorporated H+, Li+, Na+ and BMIM+— an organic cation from ionic liquid 1-butyl-3-methyl-imidazolium chloride — Nafion/Pt-based IPMCs had their electrochemical properties investigated through cyclic voltammetry, multi-step chronoamperometry and electrical impedance, as well as mass change during exhaustive actuation cycles and their chemical affinity with hydrophilic sites were analysed by quantum mechanics simulation. From the collected data, it was possible to infer that the physical-chemical aspects of counterions play a key role in device-measured property, and BMIM+ prevented early water electrolysis, providing electrochemical stability to the device. Real-time mass-monitored actuation shows that water loss occurs excessively on smaller radius counterions and although the fast reabsorption kinetics, molecular diffusion to the innermost regions of the membrane is slow and does not lead to a recovery of device’s performance. Electrochemical impedance spectroscopy data corroborate the fact that mass transport is strongly affected by both the limited ionomeric channel width and the interaction between the species and the Nafion side chains.

Solvent tunable multi-block ionomer morphology and its relationship to modulus, water swelling, directionally dependent ion transport, and actuator performance

Abstract Sulfonated penta-block ionomer (SBI) solvent cast film's ion domain spatial arrangement transitioned from random into well-connected lamellar/hexagonal structures. This micro-phase separated morphology was tunable and associated solution properties transitioning from nonpolar cyclohexane/heptane (CH) to polar tetrahydrofuran (THF). The observed morphology changes were characterized using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). SAXS revealed that average sulfonated inter-domain spacing increased asymmetrically within the film. For example, solvent cast SBI-H+ film inter-domain spacing changed from 30.8 nm using CH to 43 nm with THF. This lamellar/hexagonal morphology led to a two-fold water uptake increase from 23 wt% to 46 wt%, and an order-of-magnitude proton conductivity improvement from 4.5 mS/cm to 47.8 mS/cm. Ionomeric polymer-metal composite (IPMC) actuation performance was morphology dependent. The film with a random morphology had small actuation displacement with slow bending speed. However, well-connected ion domains enabled rapid and large bending motions.

Effect of Dehydration on the Mechanical and Physicochemical Properties of Gold- and Palladium -Ionomeric Polymer-Metal Composite (IPMC) Actuators

In this paper, we investigated the effect of dehydration on mechanical and physicochemical properties of Au (Gold) - and Pd (Palladium) -IPMC using water as solvent. By comparison, the difference of the water content of two types of IPMCs mainly depends on the morphology of surface electrodes bonded both sides of IPMC. During the dehydration process, we find that the tip deformation increases at the early stage of actuation, and then they gradually decrease with weight loss of water. And the Au-IPMC generates larger deformation than Pd-IPMC in each stage due to lower resistance of electrode layers, the maximum of which reach up to 17.4mm and 13.1mm for long strips with the same free dimensions (35mm×5mm), respectively. Their mechanical and physicochemical parameters, such as stiffness, surface resistance, capacitance and cyclic voltammograms (CVs), were examined as a function of the time, whose increase or decrease are intensely dependent on water content. The specific deformations of IPMCs are decided by combined effects of various parameters.

Three cases of laparo-assisted pancreatectomy

Sulfonated penta-block ionomer (SBI) solvent cast film's ion domain spatial arrangement transitioned from random into well-connected lamellar/hexagonal structures. This micro-phase separated morphology was tunable and associated solution properties transitioning from nonpolar cyclohexane/heptane (CH) to polar tetrahydrofuran (THF). The observed morphology changes were characterized using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). SAXS revealed that average sulfonated inter-domain spacing increased asymmetrically within the film. For example, solvent cast SBI-H+ film inter-domain spacing changed from 30.8 nm using CH to 43 nm with THF. This lamellar/hexagonal morphology led to a two-fold water uptake increase from 23 wt% to 46 wt%, and an order-of-magnitude proton conductivity improvement from 4.5 mS/cm to 47.8 mS/cm. Ionomeric polymer-metal composite (IPMC) actuation performance was morphology dependent. The film with a random morphology had small actuation displacement with slow bending speed. However, well-connected ion domains enabled rapid and large bending motions.

Electromechanical Characterization and Locomotion Control of IPMC BioMicroRobot

This paper presents the electromechanical characterization of Nafion-Pt microlegs for the development of an insect-like hexapod BioMicroRobot (BMR). BMR microlegs are built using quasi-cylindrical Nafion-Pt ionomeric polymer-metal composite (IPMC), which has 2.5 degrees of freedom. The specific manufacturing process using a laser excimer for one leg in three-dimensional configurations is discussed. Dynamic behavior and microleg characteristics have been measured in deionized water using a laser vibrometer. The use of the laser vibrometer shows the linear characteristics between the duty cycle of square wave input and displacement rate of the actuator at multiple frequencies. This linearity is used to design a servo-system in order to reproduce insect tripod walking. As well, BMR current consumption is an important parameter evaluated for each leg. Current passing throughout the IPMC membrane can result in water electrolysis. Four methods are explained for avoiding electrolysis. The hardware test bench for measurements is presented. The purpose of this design is to control a BMR for biomedical goals such as implantation into a human body. Experimental results for the proposed propulsion system are conclusive for this type of bioinspired BMR.

A Distributed Model of Ionomeric Polymer Metal Composite

This article presents a novel model of an ionomeric polymer metal composite (IPMC) material. An IPMC is modeled as a lossy RC distributed line. Unlike other electro-mechanical models of an IPMC, the distributed nature of our model permits modeling the non-uniform bending of the material. Instead of modeling the tip deflection or uniform deformation of the material, we model the changing curvature. The transient behavior of the electrical signal as well as the transient bending of the IPMC are described by partial differential equations. By implementing the proper initial and boundary conditions we develop the analytical description of the possibly non-uniform transient behavior of an IPMC consistent with the experimental results.

A mechanical model of a non-uniform ionomeric polymer metal composite actuator

This paper describes a mechanical model of an IPMC (ionomeric polymer metal composite)actuator in a cantilever beam configuration. The main contribution of our model is that itgives the most detailed description reported so far of the quasistatic mechanical behaviourof the actuator with non-uniform bending at large deflections. We also investigate a casewhere part of an IPMC actuator is replaced with a rigid elongation and demonstrate thatthis configuration would make the actuator behave more linearly. The model isexperimentally validated with MuscleSheet™ IPMCs, purchased from BioMimeticsInc.

Freeform fabrication of ionomeric polymer‐metal composite actuators

PurposeTo seek to produce low‐voltage, soft mechanical actuators entirely via freeform fabrication as part of a larger effort to freeform fabricate complete electromechanical devices with lifelike and/or biocompatible geometry and function.Design/methodology/approachThe authors selected ionomeric polymer‐metal composite (IPMC) actuators from the literature and the authors' own preliminary experiments as most promising for freeform fabrication. The authors performed material formulation and manual device fabrication experiments to arrive at materials which are amenable to robotic deposition and developed an SFF process which allows the production of complete IPMC actuators and their fabrication substrate integrated within other freeform fabricated devices. The authors freeform fabricated simple IPMC's, explored some materials/performance interactions, and preliminarily characterized these devices in comparison to devices produced by non‐SFF methods.FindingsFreeform fabricated IPMC actuators operate continuously in air for more than 4 h and 3,000 bidirectional actuation cycles. The output stress scaled to input power is one to two orders of magnitude inferior to that of non‐SFF devices. Much of this difference may be associated with process‐sensitive microstructure of materials. Future work will investigate this performance gap.Research limitations/implicationsDevice performance is sufficient to continue exploration of SFF of complete electromechanical devices, but will need improvement for broader application. The feasibility of the approach for producing devices with complex, non‐planar geometry has not been demonstrated.Practical implicationsThis work demonstrates the feasibility of freeform fabricating IPMC devices, and lays groundwork for further development of the materials and methods.Originality/valueThis work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.

Electrochemical behavior of a new type of perfluorinated carboxylate membrane/platinum composite

AbstractA new type of ionomeric polymer–metal composite (IPMC) based on various compositions of perfluoroalkylacrylate‐acryl acid copolymer with different types of counter cation has been synthesized by a radical copolymerization of fluoroalkylacrylate (FA) and acrylic acid (AA). Swelling behavior of the membranes was studied in deionized water as well as in aqueous single salt solutions (LiCl and NaCl). Swell of membrane increased with the increase in ionic content of the copolymer. Swell in deionized water was much higher than in aqueous single salt solution. To examine its performance as a new electroactive polymer, actuation force and displacement responses to DC and step voltage across the IPMC were measured. Results indicated that membranes prepared from 75/25 (FA/AA) (FA25) gave an adequate flexibility and proper hydrated state, allowing easy deflection toward the applied voltage. Surface morphology measurements (atomic force microscopy and scanning electron microscopy) showed that platinum particles are predominantly located at the surfaces. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Preparation and characterization of electroactive acrylic polymer-platinum composites

A new ionomeric polymer-metal composite (IPMC) was prepared using a cast membrane of acrylic copolymer, which was synthesized by radical copolymerization of fluoroalkyl acrylate and acrylic acid (AA). To examine its performance as a new electroactive polymer, the current and displacement responses to a step voltage applied across the IPMC were measured. The largest responses were observed when the AA content in the copolymer was 10.6 wt%.