Bio-Inspired Ionic Skin for Theranostics

The first-generation ionic skins demonstrate great advantages in the tunable mechanical properties, high transparency, ionic conductivities, and multiple sensory capacities. However, little attention is paid to the interfacial interactions among the ambient environment, natural organisms, and the artificial skins. In particularly, current ionic skins based on traditional synthetic hydrogels suffer from dehydration in vitro and lack of substance communication channels with biological tissues. Herein, this work develops a bio-inspired hydrogel to address these key challenges. The hydrogel is designed with natural moisturizing factors to lock water, biomineral ions to transmit signals, and biomimetic gradient channels to transport substances from non-living to living interfaces. It is stable in ambient condition, adhesive and hydrated on mammal skins, and capable of non-invasive point-to-point theranostics. This theranostic ionic skin realizes sensitive detection, enhanced treatment efficacy, and reduced side effects toward major diseases in vitro. It will shed light on the hydrogel bioelectronics with excellent biocompatibility, bio-protection, and bio-integration for human–machine interfaces and intelligent theranostics.     

Humidity-Induced Simultaneous Visible and Fluorescence Photonic Patterns Enabled by Integration of Covalent Bonds and Ionic Crosslinks

Stimuli-responsive photonic crystals (PCs) have been extensively studied due to their potential in fabrication of anti-counterfeiting devices and information storage. In this work, using Ca²⁺ ionic crosslinker, a cholesteric liquid crystalline network (CLCN) based PC able to simultaneously present visible and fluorescence pattern by moisture treatment is designed and prepared. The circularly polarized light from helical structure of CLCN makes the reflected pattern distinguishable under different circular polarizer, implying the unique advantage of this novel coating as anti-counterfeiting devices. More importantly, due to the thermochromic property of the liquid crystal monomers, permanent pattern is achievable by chemically crosslinking specific region at different temperature. By integrating chemically crosslinking and physically ionic crosslinking, a permanent pattern and a dynamic humidity responsive pattern can be incorporated in a single device, indicating the great potential of this novel photonic coating in information storage.     

Reversible Formation of g‐C3N4 3D Hydrogels through Ionic Liquid Activation: Gelation Behavior and Room‐Temperature Gas‐Sensing Properties

Many unique properties arise when the 3D stacking of layered materials is disrupted, originating nanostructures. Stabilization, and further reorganization of these individual layers into complex 3D structures, can be essential to allow these properties to persist in macroscopic systems. It is demonstrated that a simple hydrothermal process, assisted by ionic liquids (ILs), can convert bulk g‐C₃N₄ into a stable hydrogel. The gelation occurs through delamination of the layered structure, driven by particular interactions between the IL and the carbon nitride sheets, forming an amphiphilic foam‐like network. This study employs spectroscopic and computational tools to unravel the gelation mechanism, and provides a rational approach toward the stabilization of 2D materials in hydrogels. The solution‐processable hydrogels can also be used as building blocks of complex devices. Chemiresistive gas sensors employing g‐C₃N₄ 3D hydrogels exhibit superior response at room temperature, enabling effective gas sensing under low power conditions.     

Tuning Memristivity by Varying the Oxygen Content in a Mixed Ionic–Electronic Conductor

The rising interest shown for adaptable electronics and brain‐inspired neuromorphic hardware increases the need for new device architectures and functional materials to build such devices. The rational design of these memory components also benefits the comprehension and thus the control over the microscopic mechanisms at the origin of memristivity. In oxide‐based valence‐change memories, the control of the oxygen drift and diffusion kinetics is a key aspect in obtaining the gradual analog‐type change in resistance required for artificial synapse applications. However, only a few devices are designed with this in mind, as they are commonly built around ionic insulating active materials. This shortcoming is addressed by using a mixed ionic–electronic conductor as functional memristive material. This work demonstrates how the oxygen content in La₂NiO_4+δ (L2NO4), tuned through post‐annealing treatments, has a critical influence on the memory characteristics of L2NO4‐based memristive devices. The presence of interstitial oxygen point defects in L2NO4 affects both its structure and electrical properties. High oxygen stoichiometry in the pristine state leads to an increased electrical conductivity, ultimately resulting in an improved memory window with highly multilevel, analog‐type memory programing capabilities, desirable for analog computing and synaptic applications in particular.     

Ionic‐Association‐Assisted Viscoelastic Nylon Electrolytes Enable Synchronously Coupled Interface for Solid Batteries

Electrolyte/electrode heterointerfaces activated by unhindered charge transfer play an important role in solid‐state and flexible batteries. However, continuous electrochemical cycling and mechanical deformations cause structural dislocation and unwanted reactions. An important challenge is to ensure enduring accurate contact between the battery components. The customization of a highly viscoelastic polyamide (PA, nylon)‐based solid electrolyte to address this key issue is presented. The approach involves the use of concentrated aqueous solutions of bis(trifluoromethane)sulfonimide lithium (LiTFSI) to structurally “unzip” and relink pristine hydrogen‐bonded PA chains by bridged cation–anion association. This elaborately tailored crosslinking technique confers upon the resultant electrolyte a combination of the preferred mechanical characteristics including high viscoelasticity and reversible stretchability, together with outstanding electrochemical performance represented by high ion conductivity (2.7 × 10^?4 S cm^?1) and high anodic stability (>3 V vs Zn/Zn²⁺). Flexible batteries with a well‐integrated configuration in which synchronous electrolyte/electrode movement guarantees intimate and compatible interfaces even during extreme deformations and electrochemical stimulations, are further demonstrated. These results reveal a promising opportunity to overcome the bottleneck caused by interfacial defects for next‐generation solid batteries by reconstituting the structure of classical polymers and developing functional electrolytes.