Xia-Chao Chen,Wei-Pin Huang,Mi Hu,Ke-Feng Ren,Jian Ji
Although many approaches have been developed to encapsulate functional species into polyelectrolyte films, few of them can effectively control the final distribution of these ones. Herein, a facile strategy is proposed to spatially control the encapsulation of guest species by locally regulating the structural transformation of polyelectrolyte films. Patterned porosity is created within a film by cross-linking it selectively and then immersing it in an acidic solution. These porous regions can exhibit significantly different properties from other regions, including the ability to wick solution, a greater retention of guest species, and the capability of structural transformation. After loading guest species, the porous structures can be eliminated at saturated humidity to encapsulate the guest species into the film, leading to their patterned distribution across the film. Based on this method, various guest species, ranging from fluorescent dyes to nanoparticles, can be locally encapsulated into polyelectrolyte film, forming distinct patterns of arbitrary shapes and sizes and thus paving the way for further applications.
The development of cation exchange membranes (CEMs) with high monovalent/divalent cation selectivity has great potential for enhanced salt separation for wastewater reclamation, and layer-by-layer (LbL) self-assembly of polyelectrolyte films with high monovalent selectivities among cations has expanded the applications of such membranes. However, the structure–property relationship for constructing multilayered polyelectrolyte films with enhanced separation performance remains poorly understood. This study reports a novel CEM engineered by coating a [polyethyleneimine/polystyrene sulfonate (PEI/PSS)] n alternate electro-deposition multilayer on a polyacrylate substrate membrane. The newly developed CEM exhibited a monovalent selectivity of 4.59 for Li + /Mg 2+ with an optimal permeation of 0.16 mmol·cm −2 ·h −1 for Li + , demonstrating a competitive separation property compared to state-of-the-art permselective membranes. A detailed quantitative investigation provides the underlying insights into the monovalent selectivity for each polyelectrolyte layer. The results indicate negligible interface impedance toward monovalent cations but strengthened repulsion against divalent cations, thereby promoting a quick passage for monovalent cations while imposing temporal retardation on divalent cations during the electrodialysis (ED) process. Therefore, this study elucidates the characteristic reason for the enhanced monovalent ion permselectivity of LbL polyelectrolyte membranes in electro-driven separation processes.
Optimizing electrode structures is a promising solution for wearable electronics and flexible power sources. Nevertheless, there are still significant challenges in how to get rid of the constraints of the substrate and electrolyte on the electrode structure, thereby reducing the impact of such constraints on the elongation of supercapacitors and stabilizing the electrochemical output. In this work, a serpentine structure of low curvature (SSLC) was designed and fabricated by comparing the effect of the curvature of the turning structure on the performance of the serpentine structure. The superiority of SSLC electrodes over existing electrode structures is verified using finite element analysis (FEA) and stability experiments. Further, the SSLC electrode is used for physiological signal detection (ECG, EMG, GSR), showing excellent stability and low electrode–skin contact impedance, which is better than the medical wet electrode. A high-stretch supercapacitor (SSC) was prepared by sacrificing the substrate of the SSLC electrode and integrating the patterned electrolyte film. When the scan rate is 10 mV·s −1 , the area specific capacitance of SSC is as high as 197.9 mF·cm −2 . Under extreme deformation conditions (stretch 100%, bend 180°, twist 180°) SSC can maintain stable output. And after 10,000 charge–discharge cycles, the SSC can still output 91.96% of the initial power stably, indicating that the prepared SSC has high stretchability and stability. With highly stretchable and stable low-curvature serpentine structure electrodes, the SSC coupled with patterned electrolyte films and sacrificial substrate electrodes in this paper offer a promising solution for stretchable flexible power supplies and wearable electronics.
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