Flash Joule Heating Equipment: Centrifugal inertia-induced directional alignment of silver nanowire networks for the preparation of transparent electromagnetic interference shielding Membrane with Joule heating capability

Background

The rapid development of wireless communication technology brings convenience to people, but also produces serious electromagnetic interference (EMI) pollution, which reduces the precision and reliability of electronic equipment in the process of operation and seriously threatens people's health. Specifically, flexible EMI shielding materials with high transmittance are very much needed in many visual scenarios, such as space detection and reception optical windows, precision instrument displays, and medical electromagnetic isolation observation windows. Excellent EMI shielding efficiency (EMI SE) requires excellent electrical conductivity, but excellent electrical conductivity and dense conductive network structure is inextricably linked to the dense conductive network structure will inevitably reduce the light transmittance. Therefore, how to achieve a unique balance between the conductivity, EMI shielding performance and visible light transmittance of transparent conductive films is the key to promote the rapid development of optoelectronic devices.

One-dimensional silver nanowires (AgNW), with high aspect ratio and excellent conductivity, have great potential in the field of transparent EMI shielding, and are considered to be the most promising material to replace indium tin oxide (ITO). Despite the encouraging progress, the persistence problem of random networks lies in the presence of a large number of junctions, which not only increases the contact resistance of the network but also reduces the transmittance by decreasing the void ratio. The rational design of AgNW network structures is an effective strategy to significantly improve the conductivity and transmittance simultaneously, including prefabricated mesh structures and directional arrangements. In addition, mesh gaps ensure sufficient light transmittance, which yields high photoelectric and EMI shielding performance. Unfortunately, prefabricated mesh structures suffer from a number of problems, such as Molière's phenomenon, pattern visibility, and lack of flexibility. Together with a similar light transmittance to random networks, directional conduction networks thus show better optoelectronic performance.

The main point of this paper

Ordered Alignment AgNW Technologies:

A variety of techniques have been developed including shear coating, brush coating, strain release assembly, microfluidic arrangement, and evaporation-induced assembly.

Superwetting-induced technology:

Used to transfer self-assembled complexes of AgNW and ionic liquids to prepare transparent electrodes with light transmission of about 88% and sheet resistance of 46 Ω sq-1.

Fluid Stirring Self-Assembly Method:

Hu et al. reported the utilization of cross-assembly to obtain transparent conducting AgNW networks with transparency up to 85% and surface resistance of 2.8 Ω sq-1.

Pre-stretching method:

Developed by the research group for the preparation of highly oriented AgNW-based transparent shielding films with excellent optoelectronic properties and EMI shielding performance.

Spin coating technique:

Inspired by the high-speed rotating receiver in electrospinning, a facile strategy was demonstrated to utilize centrifugal inertial force to drive AgNW alignment along the rotational direction.

Advantages of the spin-coating technique:

Removal of excess solvent and conductive filler aggregation for high transmittance, high EMI shielding effectiveness (SE) and high Joule heating capacity.

AgNW Network Properties:

The aligned AgNW films offer low sheet resistance (4.5 Ω sq-1), high transmittance (72.9%) and excellent EMI SE (35.2 dB).

Joule heating applications:

The conductivity of the transparent shielding film produces satisfactory Joule heating (102°C @ 4V) for extreme conditions

Orientationally Aligned Silver Nanowire Networks by Rotational Spraying: Toward High Transparency and Efficient EMI Shielding

The need and challenges of transparent EMI shielding:

Transparent EMI shielding is required in specific visual scenarios, but balancing EMI shielding effectiveness (SE) and light transmission is a challenge.

AgNW network construction strategy:

A network construction strategy for directionally aligned silver nanowires (AgNW) using a rotational spraying technique is proposed to achieve high EMI SE and light transmittance.

AgNW Orientation Distribution:

The orientation distribution of AgNW is induced by the centrifugal inertia force generated by the high-speed rotating roller, which overcomes the high contact resistance problem of random networks

Properties of transparent conductive films:

The obtained films achieved a high transmittance of 72.9%, a low sheet resistance of 4.5 Ω sq-1, and ideal EMI SE values (35.2 dB in the X-band, 38.9 dB in the K-band, and a maximum SE value of 43.4 dB in the 20.4 GHz band)

Joule thermal performance and defogging/deicing capability:

The film's superior electrical conductivity gives excellent Joule thermal performance and defogging/deicing capabilities, ensuring visual clarity when shielding windows from electromagnetic waves

Summarize

In conclusion, we have employed a novel rotational spraying method to fabricate transparent conductive films with oriented aligned AgNW networks, which have comprehensive properties such as satisfactory light transmittance, excellent EMI shielding properties and Joule heating properties. The films exhibit a combination of satisfactory light transmittance, excellent EMI shielding properties, and Joule heating properties.The orientation distribution of the AgNW networks is usually induced by the centrifugal inertial force generated by a high-speed rotating roller, which results in optimal optoelectronic properties with a light transmittance of 72.9% and an Rs of 4.5 Ω sq-1.The EMI SE of the aligned AgNW films in the X-band is 35.2 dB, which is satisfactory. 35.2 dB in the X-band, which is satisfactory. In addition, the film has excellent flexibility and maintains stable EMI shielding performance after 1000 bending cycles. In addition, the transparent conductive film has excellent Joule heating properties (102 °C at 4 V), which can be used to ensure stable, visible EMI shielding at low temperatures or in foggy environments. The directional alignment structure overcomes the trade-off between conductivity and light transmittance in random AgNW networks, making it one of the best transparent EMI shielding film technologies based on AgNW.