Nanotube-AgNW Hybrid Films
Another commercially available formulation for nanotube hybrid shielding films utilizes a transparent conductive substrate comprised of silver nanowire (AgNW) encapsulated with a functionalized nanotube coating. Being environmentally stable, the nanotube coating not only protects the AgNW network from moisture, humidity, and abrasion, but also creates a nanoscale conductive shield network. Effectively a nanoscale faraday cage, higher frequency waves are suppressed. Highly transparent and easily patterned to any shape, the AgNW nanotube hybrid is an ideal candidate for applications where shielding of LCD screens, user interface buttons, enclosure windows, lighted status indicators, or operational status monitors is required while not negatively impacting their individual visibility.
Applying an optically clear adhesive, nanotube hybrid shielding films can be selectively applied with "peel & stick" ease. And measuring under 10-mile in thickness, nanotube hybrid shielding films require little space even in existing applications having minimal clearance envelope so can be added inside existing housings or enclosures without redesign.
While not delivering as universal protection as demonstrated by the MM nanotube hybrid, the AgNW nanotube hybrid can still deliver effective protection in select applications. Providing effective shielding above 20dB particularly across the predominant WiFi and cellular frequencies including 2G and 5G as shown in the figure above, AgeNT-10 provides ample protection for smartphones, tablets, or any electronic device using standard wireless connectivity signals.
Flexibility, Economy, and Agility of Fabrication
Traditionally fabricated from metal sheets formed to fit the intended enclosure, plated steel, copper and silver alloys, and aluminum have been staple materials for EMI shielding. Designing these shield enclosures must take into consideration necessary clearance envelopes to avoid interference with other components inside the device enclosure. Conductive plastics in tape, film, or foil form have also emerged as effective for anti-static applications, but have not reached widespread adoption with respect to shielding RF frequencies. While fabrication methods for metal sheets are mature and pervasive, tooling such as brakes, presses, punches and sheers require sizable capital investments and are single purpose. Completing all the multiple requisite steps to fabricate metal shields in sequence also takes days – if not weeks – to successfully complete.
Alternatively, EMI shielding created using nanotube hybrid films can be quickly and efficiently fabricated using low-cost screen printing for patterning, offering significant savings in manufacturing costs, processing time, and reduced risk of scrap. Creating EMI shield patches or circuits from nanotube hybrids is simply print, etch, and done. For applications requiring ground plane connection, screen printing conductive silver busbars onto the film makes them integral to the shield simplifying mass production. And since nanotube hybrid shielding films utilize a thin, flexible plastic substrate, they can be flexed, folded, or formed for easy incorporation into existing enclosure with limited space and small form factors.
The final advantage of a printed material or a hybrid film on metal mesh is the elimination of any required electrical contacts for grounding. Although these films could be grounded by directly printing a conductive busbar as previously mentioned, such as along the edge of the electrode matrix on a display, this is not required in order to provide the rated SE value. Nanotube hybrid shielding films could be left un-grounded, enabling them to be printed on a variety of surfaces without building in an electrical connection.
Metal mesh materials are seeing a new wave of innovation thanks to the incorporation of CNTs as a conductive additive. Hybrid CNT-AgNW on metal mesh materials with flexible substrates provide an adaptable material platform as an add-on shielding film for new or existing electronics assemblies. Thanks to the solution processability of CNTs, these materials could also be deposited with an inkjet printer in a desired pattern. Both methods give engineers a simplified way to add RFI shielding materials to new or existing electronics assemblies, providing higher SE values than existing solutions without compromising on transparency.
Increasingly sophisticated and delivering mission critical operation, electronic systems are pervasive in nearly all of our day-to-day activities. From keeping us connected to each other and an increasing array of smart devices, to ensuring our safe operation of our vehicles when commuting – especially when distracted – to delivering real-time medical diagnostic information around the globe enabling doctors in one country to treat patients in another, all depending upon wireless connections of increasing density, ensuring uninterrupted operation without interference can easily be a matter of life and death. EMI shielding provides an effective mechanism to control exposure, but traditional materials and methods do not deliver the effectivity and flexibility needed for future applications. Transparent, flexible, formable, and effective at pervasive wireless RF frequencies, nanotube hybrid shielding films offer versatility at shielding applications previously considered impossible. Proven superior in protection to even copper foil, nanotube hybrid shielding films transparently protect even in touchscreen, window, button, or other apertures in electronic devices.