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April 15, 2015: EE Times

Improving Touchscreen Products Using Silver Nanowire Conductors

The use of silver nanowires is cost-effectively accelerating the transition to next-generation flexible and wearable devices and -- beyond that -- to products we can only imagine.

It's no secret that wearable electronics are becoming increasingly popular with consumers. Designers once struggled to make hard, flat products like notebooks and tablets survive frequent wear and tear. These problems have largely been overcome, but wearable products are another game. The good news is that flexibility -- a desirable feature of things being attached to humans -- is being significantly enabled by a leap forward in materials like silver nanowire for touch-enabled products.

Silver nanowires (greatly magnified).

Who's using silver nanowire?

You will likely recognize some of the names that are already using silver nanowire-based touchscreens because they've been adopted as the transparent-conductor-of-choice by leading industry heavyweights, including Hitachi, LG, TPK, Nissha, 3M, Okura, and many others.

Wearability = flexibility

What is already here in personal computing devices, in addition to mind-boggling electronics size reduction, is wearability. Making that happen means the human interface must radically evolve. Brittle glass is out. Flexible electronics and interfaces are in. They provide enhanced portability and durability, and also provide virtually unlimited design flexibility. Flexible touch displays essentially equate to flexible ergonomics. Imagine unbreakable phone screens that flex instead of shattering when dropped. Consider folding a seven-inch tablet so it slips into your pocket. How about a display that wraps around your arm? Or what about a huge public display wrapping around a pillar or a building like neon lighting can? We are driving toward products like these, and these products are creating increasing demand for flexible, bendable, and rollable touch screens. As more product designers become aware of silver nanowire touch displays, we'll be seeing more insanely great new products.

Consumer electronic devices that are coming won't look like yesterday's clunky boxes. Tablets and laptops are increasingly thinner, and even monitors and kiosks are becoming sleek and aesthetically pleasing. In turn, this is driving the demand for thinner, lighter components. Apart from anything else, electronic components with reduced mass tend to be more rugged and durable.

The flexibility of silver nanowires -- along with their transmission and conductive properties -- are enablers for an array of existing and forthcoming electronic displays and consumer wearables, as well as IoT inventions for as-yet unimagined applications.

The Cambrios laboratory where new materials like state-of-the-art silver nanowires are created.

Brighter, stronger, more sensitive, lower power...

There are several factors that make silver nanowires a material ideally suited to new products for the "touch age." Let's start by noting that touchscreens should be thin, light, visible in various ambient light conditions, highly responsive, and -- perhaps most importantly -- lower-cost.

The most popular touchscreen technology is projected capacitance, or pro-cap. At the core is a transparent conductor -- a layer of material that needs to conduct electricity while remaining transparent so as to allow light from the underlying display to shine through the screen. Indium tin oxide (ITO), the legacy conductor material, is neither very conductive nor transparent compared with silver nanowires. It's also too brittle for flexible display and touch applications.

Forthcoming generations of both smaller and larger touch interfaces need to be very responsive; also, the display needs to be bright and visible in all types of ambient lighting. This requires notably more highly conductive transparent conductors with high transmission ability. Silver nanowire delivers on all counts.

Transparent conductors may also be applied as electrodes for LCD, OLED, thin film photovoltaic cells, shutters for 3D TVs, and applications that are yet to be imagined. In general, the requirements are the same. This means higher conductivity, better light transmission, and no side-effects like moiré or pattern visibility, along with the ability to support flexible touch screens. OEM systems companies naturally want all of these features at less cost than traditional technologies.

…and thinner!

Single-layer touch sensors are in demand for tablets, mobile phones, and -- doubtless -- whatever comes next. A single-layer approach offers notably lower cost because there are fewer layers of adhesives and conductors in the touchscreen stack. Newer products also have higher performance requirements to meet or exceed competitive offerings, making silver nanowires an ideal fit in the product development race.

Recently, a seven-inch, single-layer design using silver nanowires was demonstrated. It's twice the size of what's possible with ITO. The narrow line/space requirements rule out competing metal mesh technologies as well. This single-layer touch sensor offers multi-touch capability (we have 10 fingers), very high transmission (over 90 percent) and is ideally suited for price-sensitive mobile consumer electronics products. Furthermore, it can be matched with either a glass or plastic cover lens offering OEMs notably increased product design freedom.

Less to make

There's more good news. Overall, silver nanowire-based touchscreens range from slightly less to significantly lower cost than equivalent ITO film-based solutions. The manufacturing process doesn't use chemicals and there are no waste disposal problems, so it's a greener way of making new touchscreens.

The bottom line is that specifying silver nanowire-based touch technology doesn't have a downside. Overall, its costs range from slightly less to significantly less than the cost of equivalent ITO, film-based solutions. Its advantages are numerous. The material is cost-effectively accelerating the transition to next-generation flexible and wearable devices and -- beyond that -- to products we can only imagine.

Sri Peruvemba is a vice president at Cambrios Technologies Corporation. Cambrios provides innovative solutions using nanotechnology. Its silver nanowire-based transparent conductors simplify electronics manufacturing and improve end-product cost and performance for electronic devices.

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