Printed Self-Healing Stretchable Electronics for Bio-signal Monitoring and Intelligent Packaging

Integrating self-healing capabilities into printed stretchable electronic devices is important for improving performance and extending device life. However, achieving printed self-healing stretchable electronic devices with excellent device-level healing ability and stretchability while maintaining outstanding electrical performance remains challenging. Herein, a series of printed device-level self-healing stretchable electronic devices is achieved by depositing liquid metal/silver fractal dendrites/polystyrene-block-polyisoprene-block-polystyrene (LM/Ag FDs/SIS) conductive inks onto a self-healing thermoplastic polyurethane (TPU) film via screen printing method. Owing to the fluidic properties of the LM and the interfacial hydrogen bonding and disulfide bonds of TPU, the as-obtained stretchable electronic devices maintain good electronic properties under strain and exhibit device-level self-healing properties without external stimulation. Printed self-healing stretchable electrodes possess high electrical conductivity (1.6 × 105 S m-1), excellent electromechanical properties, and dynamic stability, with only a 2.5-fold increase in resistance at 200% strain, even after a complete cut and re-healing treatment. The printed self-healing capacitive stretchable strain sensor shows good linearity (R2 ≈0.9994) in a wide sensing range (0%-200%) and is successfully applied to bio-signal detection. Furthermore, the printed self-healing electronic smart label is designed and can be used for real-time environmental monitoring, which exhibits promising potential for practical application in food preservation packaging.

Fully-Printed Flexible Aqueous Rechargeable Sodium-Ion Batteries

The flexible aqueous rechargeable sodium-ion batteries (ARSIBs) are a promising portable energy storage system that can meet the flexibility and safety requirements of wearable electronic devices. However, it faces huge challenges in mechanical stability and facile manufacturing processes. Herein, the first fully-printed flexible ARSIBs with appealing mechanical performance by screen-printing technique is prepared, which utilizes Na3 V2 (PO4 )2 F3 /C (NVPF/C) as the cathode and 2% nitrogenous carbon-loaded Na3 MnTi(PO4 )3 /C (NMTP/C/NC) as the anode. In particular, the organic co-solvent ethylene glycol (EG) is cleverly added to 17 m (mol kg-1 ) NaClO4 electrolyte to prepare a 17 m NaClO4 -EG mixed electrolyte. This mixed electrolyte can withstand low temperatures of -20 °C in practical applications. Encouragingly, the fully-printed flexible ARSIBs (NMTP/C/NC//NVPF/C) exhibit a discharge capacity of 40.1 mAh g-1 , an energy density of 40.1 Wh kg-1 , and outstanding cycle performance. Moreover, these batteries with various shapes can be used as an energy wristband for an electronic watch in the bending states. The fully-printed flexible ARSIBs in this work are expected to shed light on the development of energy for wearable electronics.

An All-Printed, Fast-Response Flexible Humidity Sensor Based on Hexagonal-WO3 Nanowires for Multifunctional Applications

The utilization of printing techniques for the development of high-performance humidity sensors holds immense significance for various applications in the fields of the Internet of Things, agriculture, human healthcare, and storage environments. However, the long response time and low sensitivity of current printed humidity sensors limit their practical applications. Herein, a series of high-sensing-performance flexible resistive-type humidity sensors is fabricated by the screen-printing method, and hexagonal tungsten oxide (h-WO3 ) is employed as the humidity-sensing material due to its low cost, strong chemical adsorption ability, and excellent humidity-sensing ability. The as-prepared printed sensors exhibit high sensitivity, good repeatability, outstanding flexibility, low hysteresis, and fast response (1.5 s) in a wide relative humidity (RH) range (11-95% RH). Furthermore, the sensitivity of humidity sensors can be easily adjusted by altering the manufacturing parameters of the sensing layer and interdigital electrode to meet the diverse requirements of specific applications. The printed flexible humidity sensors possess immense potential in various applications, including wearable devices, non-contact measurements, and packaging opening state monitoring.

A Continuous Gradient Chemical Reduction Strategy of Graphene Oxide for Highly Efficient Evaporation-Driven Electricity Generation

Spontaneously harvesting electricity through a water evaporation process is renewable and environmentally friendly, and provides a promising way for self-powered electronics. However, most of evaporation-driven generators are suffering from a limited power supply for practical use. Herein, a high-performance textile-based evaporation-driven electricity generator based on continuous gradient chemical reduced graphene oxide (CG-rGO@TEEG) is obtained by a continuous gradient chemical reduction strategy. The continuous gradient structure not only greatly enhances the ion concentration difference between the positive and negative electrodes but also significantly optimizes the electrical conductivity of the generator. As a result, the as-prepared CG-rGO@TEEG can generate a voltage of 0.44 V and a considerable current of 590.1 µA with an optimized power density of 0.55 mW cm-3 when 50 µL of NaCl solution is applied. Such scale-up CG-rGO@TEEGs can supply sufficient power to directly drive a commercial clock for more than 2 h in ambient conditions. This work offers a novel approach for efficient clean energy harvesting based on water evaporation.