Multifunctionality in polymers facilitates their application in emerging technologies. Electrical fields are a preferred stimulus because of the speed and ease of application to bulk polymers. While ...a wide range of electrically triggered actuators are developed, and electrically controlled adhesion between gels is demonstrated, modification of bulk mechanical properties via electrical stimuli remains elusive. Polymers with covalently incorporated ionic charge (polyelectrolytes) should be well suited to achieving this goal since the mechanical properties depend on electrostatic interactions and these charges are intrinsically susceptible to electric fields. Molecular dynamics simulations are utilized here to investigate whether electric fields can modulate the mechanical properties of polyelectrolytes and to understand the governing mechanisms. Mechanical property modulation by electric field is found to be sensitive to the charge distribution—charges must be tightly attached to the polymer backbone, and responsivity is greater if a single backbone contains both positive and negative charges. The dominant mechanisms are reorientation and stretching of the polymer chains, which also elongate the ionic clusters to maintain strong electrostatic interactions throughout deformation. These insights are critical for future experimental realization of polymers with electric field regulated mechanical properties.
This manuscript proposes and uses molecular dynamics simulations to investigate a new multifunctional capability for polymers—regulation of its mechanical properties by an electric field. The study reveals first, that such regulation is possible, and second, that charge cluster reorganization and chain orientation are the dominant mechanisms for manipulating mechanical properties.
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•Development of a flow microdevice with programmable in situ hydrogel formation.•Utilization of Fe-alginate hydrogel as the electric stimuli-responsive material.•On-demand release of ...Fe2+ ions for controlled reactive radical formation.•Portable microfluidic device for continuous BPA degradation at the pollution source.•Model-based design for iterative optimization and process intensification.
An innovative electrochemical microreactor leveraging redox-responsive hydrogels for the targeted removal of organic pollutants has been presented in this study. The centrepiece is a redox-responsive alginate hydrogel cross-linked with iron ions, capable of controlling the release of Fe ions by an external electrical stimulus. The Fe ions were used to activate persulfate, leading to the formation of reactive sulfate and hydroxyl radicals in situ. The system was tested for the continuous degradation of organic pollutants by radical oxidation using bisphenol A (BPA) as a model system. This unique, responsive feature of the alginate hydrogel enables its modulation and thus the removal of BPA on demand. In continuous operation, a BPA removal efficiency of over 94 % was achieved, demonstrating the enormous potential of microfluidic setup for the environmental remediation of various organic pollutants. By tailoring the process conditions, such as the residence time, even a complete removal of BPA was achieved. The robust and portable design should enable the utilization of such a system at the site of contamination. Due to the efficient process control achieved through microfluidic design, the study further delves into the adaptability of this system to different environmental matrices and showcases its potential as a promising solution to the increasing global threat of water pollution. Thereby, this research opens up new strategies for niche-oriented pollution management, including model-based design approaches. The CFD model was applied to simulate and optimize process conditions, enabling further process intensification.
Multifunctionality in polymers facilitates their application in emerging technologies. Electrical fields are a preferred stimulus because of the speed and ease of application to bulk polymers. While ...a wide range of electrically triggered actuators are developed, and electrically controlled adhesion between gels is demonstrated, modification of bulk mechanical properties via electrical stimuli remains elusive. Polymers with covalently incorporated ionic charge (polyelectrolytes) should be well suited to achieving this goal since the mechanical properties depend on electrostatic interactions and these charges are intrinsically susceptible to electric fields. Molecular dynamics simulations are utilized here to investigate whether electric fields can modulate the mechanical properties of polyelectrolytes and to understand the governing mechanisms. Mechanical property modulation by electric field is found to be sensitive to the charge distribution—charges must be tightly attached to the polymer backbone, and responsivity is greater if a single backbone contains both positive and negative charges. The dominant mechanisms are reorientation and stretching of the polymer chains, which also elongate the ionic clusters to maintain strong electrostatic interactions throughout deformation. Furthermore, these insights are critical for future experimental realization of polymers with electric field regulated mechanical properties.
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Corticosteroids such as dexamethasone are first line ophthalmic treatment for non-infectious posterior uveitis. Corticosteroids are often administered via intravitreal injection to ...treat this condition with frequent injections associated with poor treatment adherence and complications such as endophthalmitis. Current ocular implants provide sustained corticosteroid release at predetermined rates and lack the ability for dose individualisation. This study describes the successful fabrication of electrically responsive macroporous polypyrrole (PPy) thin films, and their subsequent application to triggered dexamethasone release. Colloidal crystal films composed of 370nm polymethylmethacrylate colloids were first deposited on ITO coated glass substrates, and subsequently used as sacrificial templates for the fabrication of high surface area, 3-dimensionally ordered macroporous PPy inverse opal (PPy IO) thin films. SEM, UV–Vis reflectance and cyclic voltammetry measurements established that the redox state of the PPy IO films could be controlled via electrical stimulation, which in turn influences both porosity and optical properties of the films. Incorporation of the anti-inflammatory corticosteroid, dexamethasone phosphate (DexP), in the PPy IO films during their fabrication resulted in an effective delivery platform for triggered DexP release. A sustained release profile was observed for the PPy IO–DexP films, bursts of release could be triggered by electrical stimulation. The amount of DexP released from the PPy IO–DexP films was significantly higher than that released from the conventional non-porous PPy–DexP films of comparable mass. Results suggest that electrically responsive PPy IO structures are highly suitable for on-demand drug delivery applications. This technology may enable physicians to fine-tune the required dose according to disease state and patients’ needs to enhance the safety and efficacy of corticosteroid treatment.
Reclaiming kinetic energy from vibrating machines holds great promise for sustainable energy harvesting technologies. Nevertheless, the impulsive current induced by vibrations is incompatible with ...conventional energy storage devices. The energy‐management system necessitates novel designs of soft materials for lightweight, miniaturized, and integrated high‐frequency electrochemical devices. Here, this work develops a conductive hydrogel with an electro‐responsive polymeric network. The electro‐responsive breathing transition of the crosslinking points facilitates the expeditious formation of a localized electrolyte layer. This layer features an exceedingly high local charge density, surpassing that of a saturated electrolyte solution by an order of magnitude, and thus enabling rapid charge transport under the influence of an applied voltage. The micro‐capacitor based on the gel exhibits record‐high capacitance of ≈2 mF cm−2 when the frequency of energy input reaches up to 104 Hz. This work also demonstrates a prototype battery charger that harvests energy from a running car engine. This study presents a feasible strategy for waste energy recycling using integrated electrochemical devices, opening a new avenue for ambient energy management.
Conductive hydrogel, engineered with a PEDOT:PSS network featuring dynamic crosslinking points, exhibits electro‐responsive behavior for efficient energy storage. The high‐density charge surfaces enable breathing transitions under voltage, offering superior frequency compatibility. The flexible energy harvester based on such hydrogel reclaims kinetic energy, suggesting topological‐structure engineering of hydrogels as a promising route for ambient energy management.
Electro-responsive dynamic hydrogels, which possess robust mechanical properties and precise spatiotemporal resolution, have a wide range of applications in biomedicine and energy science. However, ...it is still challenging to design and prepare electro-responsive hydrogels (ERHs) which have all of these properties. Here, we report one such class of ERHs with these features, based on the direct current voltage (DCV)-induced rearrangement of sodium dodecyl sulfate (SDS) micelles, where the rearrangement can tune the hydrogel networks that are originally maintained by the SDS micelle-assisted hydrophobic interactions. An enlarged mesh size is demonstrated for these ERHs after DCV treatment. Given the unique structure and properties of these ERHs, hydrophobic cargo (thiostrepton) has been incorporated into the hydrogels and is released upon DCV loading. Additionally, these hydrogels are highly stretchable (>6000%) and tough (507 J/m2), showing robust mechanical properties. Moreover, these hydrogels have a high spatiotemporal resolution. As the cross-links within our ERHs are enabled by the non-covalent (i.e., hydrophobic) interactions, these hydrogels are self-healing and malleable. Considering the robust mechanical properties, precise spatiotemporal resolution, dynamic nature (e.g., injectable and self-healing), and on-demand drug delivery ability, this class of ERHs will be of great interest in the fields of wearable bioelectronics and smart drug delivery systems.
•The hybrid material was synthesized from the in-situ growth of MNP on the GP surface.•The highest storage modulus sensitivity was obtained from the 0.5%v/v MNP-GP/PU with the value of 3.97 at the ...electric field strength of 2kV/mm.•The 0.5%v/v MNP-GP/PU exhibited the largest bending distance of 13.65mm under electric field of 500V/mm.•The 3.0%v/v MNP-GP/PU yielded the maximum bending distance of 15.35mm under magnetic field strength of 1650G.•The composites showed excellent recoverability and fast response under both electric and magnetic fields.
Dual responsive material composed of magnetite nanoparticle (MNP) and graphene nanosheet (GP) as a hybrid filler and polyurethane (PU) as an electrostrictive matrix was fabricated. The hybrid filler was synthesized by the in-situ growth of MNP on the GP surface. The obtained hybrid particles behaved simultaneously as a superparamagnetic and conducting material. The hybrid-composites possessed electronic polarization and high response towards electric field, as they showed excellent recoverability and fast response during the temporal test under electric field. The highest storage modulus sensitivity was obtained from the 0.5%v/v MNP-GP/PU at the value of 3.97 under the applied electric field of 2kV/mm. In the deflection experiment, the 0.5%v/v MNP-GP/PU composite exhibited the largest bending distance of 13.65mm under the electric field of 500V/mm. On the other hand, the 3.0%v/v MNP-GP/PU yielded the maximum bending of 15.35mm under the magnetic field of 1650G.
Multi-functional materials in actuator applications have been developed toward reversibility and sensitivity under various actuating fields. In this work, magneto-electro-responsive materials ...consisting of a polyurethane (PU) matrix and its composites embedded with magnetite nanoparticles (MNP) as a dispersed phase were fabricated to tailor the electromechanical properties and bending performance under electric, magnetic, and electromagnetic fields. Due to the superior characteristics of MNP over other magnetic materials, the composites fabricated with electronic polarization were highly responsive under electric field. The highest storage modulus sensitivity belonged to the 1.0% v/v MNP/PU composite which possessed the value of 3.46 at the electric field 2kVmm−1. Moreover, all of the PU composites behaved as an electrostrictive material in which the stress depended quadratically on the electric field. It was demonstrated that the PU composites also possessed very good recoverability, fast response (<15s) and large bending angle relative to that of pristine PU under applied electric field. Interestingly, the steady state storage modulus response was attained within the first electrical actuation cycle and the PU composite was a fully reversible material. In addition, it was shown that superparamagnetism was a common characteristic of all fabricated composites under magnetic field. The 3.0%v/v MNP/PU composite provided the largest bending distance up to 23.60mm, and 14.10mm under the magnetic field of 5000G, and the electromagnetic field of 320G, respectively. In summary, the MNP/PU composite material is a potential candidate to be used as a smart material under the influences of electric and/or magnetic fields over other existing dielectric materials.
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•MNP/PU composites exhibit a superparamagnetic behavior.•MNP/PU composites show full reversibility under electric field.•1.0% v/v MNP/PU composite provides the highest sensitivity of 3.4.•MNP improves the electrical and magnetic responses of the PU matrix.
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