A flame-retardant and conductive fabric-based triboelectric nanogenerator: Application in fire alarm and emergency evacuation

Development of flexible high-performance PDMS-based triboelectric nanogenerator using nanogratings

This article investigates the performance of a contact-mode Triboelectric Nanogenerator (TENG) utilizing polydimethylsiloxane (PDMS) with nano gratings as a dielectric in a metal-dielectric configuration. The evaluation encompasses the impact of gratings, tapping frequency, various load conditions, and contact area on the TENG performance. The fabrication involves spin-coating PDMS onto a master mold to create the device. Experimental measurements reveal a significant enhancement of 97% in open-circuit voltage by introducing gratings on PDMS. Furthermore, as the tapping frequency increases from 1 Hz to 3 Hz, there is a corresponding rise of 108% in output voltage. The influence of load resistance on TENG output performance demonstrates its ability to drive different loads efficiently. Moreover, enlarging the contact area of the device substantially increases the open-circuit voltage. A device with a 400 mm2 contact area can generate a voltage of 80 V at a low frequency of 3 Hz, indicating the importance of considering device size and contact area for specific applications. A practical circuit integrating a TENG with a full-wave bridge rectifier demonstrates energy harvesting capabilities by successfully illuminating a light-emitting diode (LED) and charging various capacitors. The fabricated devices exhibit better performance along with a cost-effective and easy fabrication process.

Nylons with Applications in Energy Generators, 3D Printing and Biomedicine

Linear polyamides, known as nylons, are a class of synthetic polymers with a wide range of applications due to their outstanding properties, such as chemical and thermal resistance or mechanical strength. These polymers have been used in various fields: from common and domestic applications, such as socks and fishing nets, to industrial gears or water purification membranes. By their durability, flexibility and wear resistance, nylons are now being used in addictive manufacturing technology as a good material choice to produce sophisticated devices with precise and complex geometric shapes. Furthermore, the emergence of triboelectric nanogenerators and the development of biomaterials have highlighted the versatility and utility of these materials. Due to their ability to enhance triboelectric performance and the range of applications, nylons show a potential use as tribo-positive materials. Because of the easy control of their shape, they can be subsequently integrated into nanogenerators. The use of nylons has also extended into the field of biomaterials, where their biocompatibility, mechanical strength and versatility have paved the way for groundbreaking advances in medical devices as dental implants, catheters and non-absorbable surgical sutures. By means of 3D bioprinting, nylons have been used to develop scaffolds, joint implants and drug carriers with tailored properties for various biomedical applications. The present paper aims to collect evidence of these recently specific applications of nylons by reviewing the literature produced in recent decades, with a special focus on the newer technologies in the field of energy harvesting and biomedicine.

Preparation of strong and tough conductive hydrogel based on Grafting, Fe3+-Catechol complexations and salting out for triboelectric nanogenerators

The development of a strong and tough conductive hydrogel capable of meeting the strict requirements of the electrode of a hydrogel-based triboelectric nanogenerator (H-TENG) remains an enormous challenge. Herein, a robust conductive polyvinyl alcohol (PVA) hydrogel is designed via a three-step method: (1) grafting with 3,4-dihydroxy benzaldehyde, (2) metal complexation using ferric chloride (FeCl3) and (3) salting-out using sodium citrate. The hydrogel contains robust crystalline PVA domains and reversible/high-density non-covalent interactions, such as hydrogen bonding, π-π interactions and Fe3+-catechol complexations. Benefiting from the crystalline domains, the hydrogel can resist external forces to the hydrogel network; meanwhile, the reversible/high-density of non-covalent interactions can impart gradual and persistent energy dissipation during deformation. The hydrogel possesses multiple cross-linked networks, with 6.47 MPa tensile stress, 1000 % strain, 35.24 MJ/m3 toughness and 37.59 kJ/m2 fracture energy. Furthermore, the inter-connected porous hydrogel has an ideal structure for ionic-conducing channels. The hydrogel is assembled into an H-TENG, which can generate open circuit voltage of ∼ 150 V, short-circuit current of ∼ 3.0 μA, with superb damage immunity. Subsequently, road traffic monitoring systems are innovatively developed and demonstrated by using the H-TENG. This study provides a novel strategy to prepare superiorly strong and tough hydrogels that can meet the high demand for H-TENGs.

Recent Progress in Two-Dimensional Nanomaterials for Flame Retardance and Fire-Warning Applications

Graphene-like 2D nanomaterials, such as graphene, MXene, molybdenum disulfide, and boron nitride, present a promising avenue for eco-friendly flame retardants. Their inherent characteristics, including metal-like conductivity, high specific surface area, electron transport capacity, and solution processability, make them highly suitable for applications in both structural fire protection and fire alarm systems. This review offers an up-to-date exploration of advancements in flame retardant composites, utilizing pristine graphene-like nanosheets, versatile graphene-like nanosheets with multiple functions, and collaborative systems based on these nanomaterials. Moreover, graphene-like 2D nanomaterials exhibit considerable potential in the development of early fire alarm systems, enabling timely warnings. This review provides an overview of flame-retarding and fire-warning mechanisms, diverse multifunctional nanocomposites, and the evolving trends in the development of fire alarm systems anchored in graphene-like 2D nanomaterials and their derivatives. Ultimately, the existing challenges and prospective directions for the utilization of graphene-like 2D nanomaterials in flame retardant and fire-warning applications are put forward.