Electromagnetic interference (EMI) can harm smartphones, tablets, chips, drones, wearables, aircraft, and human health. EMI is increasing with the explosive proliferation of devices that generate it. A technique was developed to produce relatively low-cost EMI-blocking composite films.
To fashion the films, spin-spray layer-by-layer processing (SSLbL) was employed. The system uses mounted spray heads above a spin coater that deposit sequential nanometer-thick monolayers of oppositely charged compounds on a component, producing high-quality films in much less time than by traditional methods such as dip coating.
The process creates flexible, semitransparent EMI-shielding film comprising hundreds of alternating layers of carbon nanotubes (CNT), an oppositely charged titanium carbide called MXene — a family of carbide flakes — and poly-electrolytes. MXene has the dual benefits of being both adsorbing (easily adheres to a surface) and conductive, which is important for blocking EMI. Since the film is semi-transparent, it has the benefit of being applicable as EMI shielding for devices with display screens, such as smartphones.
The SSLbL method also confers nanometer-level control over the architecture of the film, allowing manufacturers to change specific qualities such as conductivity or transparency because it allows for discrete changes in the composition of each layer. By contrast, films comprising a monolayer mélange of nanoparticles, polyelectrolytes, and graphene in a matrix cannot be modified in this manner. The MXene-CNT composite films also demonstrated high conductivity, a property critical to electromagnetic shielding because it dissipates EM pulses across the film's surface, weakening and dispersing it.
While manufacturers have shown interest in EMI shielding made of carbon nanotubes and graphene combined with conductive polymer composites, until now, a relatively fast, inexpensive means of creating an optimal mix of these qualities on a thin flexible film was not possible. While spin-spraying limits component size, in theory, the system could create EMI shielding for devices and components equivalent in diameter to the 12” wafers for which spin-coating is frequently employed as a coating mechanism in the semiconductor industry.