Flexible and transparent silver nanowires/biopolymer film for high-efficient electromagnetic interference shielding

Silver nanowires/cellulose flexible transparent conductive films for electromagnetic interference shielding and electrothermal conversion

Currently, electromagnetic shielding materials need to meet the characteristics of lightweight, high transmittance, and robust conductivity. Silver nanowires (AgNWs) have progressively found applications in recent years owing to their excellent aspect ratio, conductivity, and flexibility. The properties of AgNWs vary with different aspect ratios, and the length and diameter of AgNWs often exert diverse influences on the photoelectric properties of conductive films. In this study, we combined AgNWs with hydroxypropyl methylcellulose (HPMC) and employed a directional stacking arrangement method to apply AgNWs onto the PET substrate, investigating the properties of four distinct aspect ratios of AgNWs (1000, 750, 625, and 531). Ultimately, the prepared four films achieved electromagnetic shielding capabilities ranging from 26.6 dB to 32.8 dB, with a transmittance range of 89.8% to 94.6%, showing excellent electromagnetic shielding properties. Moreover, the prepared films showed an exceedingly low roughness value (RMS = 7.07 nm), remarkable flexibility, and superior oxidation resistance with the facilitation of HPMC. The films also showed exceptional electrothermal conversion prowess, achieving saturation temperature within a mere 8 seconds, thereby displaying a rapid thermal response. Furthermore, when a voltage of 4 V was applied, the temperature of the thin film remained essentially constant for a duration of 2500 seconds, highlighting its admirable thermal stability, which is of great significance for the development of flexible and transparent electromagnetic shielding materials in the future.

Transparent and Flexible Composite Films with Excellent Electromagnetic Interference Shielding and Thermal Insulating Performance

As the working environment becomes more complex, the visualization of windows in electronic devices increasingly requires transparent and flexible electromagnetic interference (EMI) shielding films. There is a need for materials with EMI shielding properties, while maintaining excellent high light transmission and good thermal insulation. However, the preparation of such multifunctional materials remains challenging due to the respective mechanisms of action of the different properties. Herein, a multilayer structure strategy is proposed to fabricate transparent and flexible indium tin oxide (ITO)/silver nanowire (AgNW) composite films, achieving a multifunctional integration of high light transmission, strong EMI shielding, and good thermal insulation properties of the composite films. Simultaneously, the layered structure was designed and the potential optimization mechanism of the EMI shielding performance of the composite film was analyzed, providing great flexibility for the preparation of transparent composite films. The combination of excellent EMI shielding performance, outstanding near-infrared shielding performance, and high light transmittance makes the ITO/AgNW (IA) composite films promising for abundant potential applications.

Flexible, Transparent, and Hazy Composite Cellulosic Film with Interconnected Silver Nanowire Networks for EMI Shielding and Joule Heating

An optical transparent and hazy film with admirable flexibility, electromagnetic interference (EMI) shielding, and Joule heating performance meeting the requirements of optoelectronic devices is significantly desirable. Herein, a cellulose paper was infiltrated by epoxy resin to fabricate a transparent cellulose paper (TCP) with high transparency, optical haze, and favorable flexibility, owing to effective light scattering and mechanical enhancement of the cellulose network. Moreover, a highly connected silver nanowire (AgNW) network was constructed on the TCP substrate by the spray-coating method and appropriate thermal annealing technique to realize high electrical conductivity and favorable optical transmittance of the composite film at the same time, followed by coating of a polydimethylsiloxane (PDMS) layer for protection of the AgNW network. The obtained PDMS/AgNWs/TCP composite film features considerable optical transmittance (up to 86.8%) and haze (up to 97.7%), while satisfactory EMI shielding effectiveness (SE) (up to 39.1 dB, 8.2-12.4 GHz) as well as strong mechanical strength (higher than 41 MPa) were achieved. The coated PDMS layer prevented the AgNW network from falling off and ensured the long-term stability of the PDMS/AgNWs/TCP composite film under deformations. In addition, the multifunctional PDMS/AgNWs/TCP composite film also exhibited excellent Joule heating performance with low supplied voltages, rapid response, and sufficient stability. This work demonstrates a novel pathway to improve the performance of multifunctional transparent composite films for future advanced optoelectronic devices.

Optically Transparent Broadband Microwave Absorber by Graphene and Metallic Rings

The demand for optically transparent microwave absorbers has attracted increasing interest among researchers in recent years. However, integrating broadband microwave absorption and high optical transparency remains a challenge. This report demonstrates a scheme for broadband microwave absorbers, featuring a 90% absorption bandwidth of 10 GHz covering a frequency range of 25.2-35.2 GHz and high compatibility with good optical transparency in a wide band from the visible to infrared. The absorber is based on a Jaumann structure composed of two graphene sheets sandwiched by dielectric and backed by an arrayed-metallic-rings sheet. Guided by derived formulas, this absorber exhibits complete absorption if the sheet resistance of graphene is close to 500 Ω sq^-1. The bandwidth and center frequency of the absorption spectra can be readily tuned simply via changes in the thickness of the dielectric between the graphene films and arrayed-metallic-rings sheet. Moreover, the absorber is insensitive to the incident angle of radiation and can achieve broadband and near-unity absorption even at oblique incidence. The graphene-based absorber proposed herein provides a viable solution for effectively integrating broadband and near-unity microwave absorption with high optical transparency, thereby enabling widespread applications in optics, communications, and solar cells.

Multifunctional Integrated Transparent Film for Efficient Electromagnetic Protection

Silver nanowire (Ag NW) has been considered as the promising building block for the fabrication of transparent electromagnetic interference (EMI) shielding films. However, the practical application of Ag NW-based EMI shielding films has been restricted due to the unsatisfactory stability of Ag NW. Herein, we proposed a reduced graphene oxide (rGO) decorated Ag NW film, which realizes a seamless integration of optical transparency, highly efficient EMI shielding, reliable durability and stability. The Ag NW constructs a highly transparent and conductive network, and the rGO provides additional conductive path, showing a superior EMI shielding effectiveness (SE) of 33.62 dB at transmittance of 81.9%. In addition, the top rGO layer enables the hybrid film with reliable durability and chemical stability, which can maintain 96% and 90% EMI SE after 1000 times bending cycles at radius of 2 mm and exposure in air for 80 days. Furthermore, the rGO/Ag NW films also possess fast thermal response and heating stability, making them highly applicable in wearable devices. The synergy of Ag NW and rGO grants the hybrid EMI shielding film multiple desired functions and meanwhile overcomes the shortcomings of Ag NW. This work provides a reference for preparing multifunctional integrated transparent EMI shielding film.