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Most transparent touch sensors today are built using Indium Tin Oxide [ITO]. ITO is a rare ceramic-like material that is mostly produced in China. The reason that ITO is in most touch sensors today is because ITO has good conductivity, good transparency and a slow decay rate. But ITO has many disadvantages, one of those is that ITO is expensive and the manufacturing process to is also expensive and complicated.

The manufacturing process to build an ITO sensor consists of spouting the ITO powder over glass, cooking the ITO so it melts, creating a conductive layer and then etching the sensing circuit on the conductive layer by use of photolithography or laser lithography. All these manufacturing steps add extra cost to the production of an ITO sensor. ITO also has other disadvantages, like supply constrains and environmental concerns about the ITO mining process. These constrains has pushed the market to search for an alternative to ITO.

Silver Nanowires

Silver Nanowires is an ink-like substance that is only produced in Japan by Cambrios for Nissha Printing under the ClearOhm brand name. Silver Nanowires don't require to be melted like ITO does, so it can be printed directly on thin films. The only disadvantage of ClearOhm is its transparency goes down on bigger screen sizes that requires bigger conductive lines.

Recently Apple (AAPL) introduced the iPad Mini with avery thin touch sensor supplied exclusively by Nissha Printing. The sensor uses a G/F2 stack that means that the electrode layer is placed on the top and bottom ends of a film, which is then laminated onto the cover glass. Examining the thickness of the sensor film has convinced me that this touch sensor was build using Silver Nanowires instead of ITO, because I don't see how it is possible to attach ITO to both sides of an super thin film. Because the small size of the iPad Mini transparency should not have been an issue.

Metal Mesh

Another very promising technology is metal mesh technology; in this case copper is used to print the touch sensor on film. The advantages of metal mesh is that it is extremely conductive and economical. The trick here is to be able to print the copper lines so thin that they are virtually invisible, so transparency is the big issue.

Right now, there are two companies dealing with this technology, one is UniPixel (UNXL) and the other one is Atmel (ATML). Both companies have achieved copper lines under 5 microns. Atmel boasts that their new touch sensor (called XSense) has transparency comparable to that of ITO. UniPixel recently announced that they are ready to start production of their metal mesh sensor (named UniBoss), while Atmel has already started production and commercial shipments were delivered to OEMs in October. There has not been a side by side comparison between UniBoss and XSense, that would be interesting to see. Atmel of course is shipping XSense with its own line of touch controllers (maXTouch) while UniPixel has partnered with Texas Instruments (TXN) and others to create touch controllers for UniBoss and partnered with N-trig to custom design the touch sensor circuitry layer. Both companies have announced that volume ramp up will start in the second half 2013.

In-Cell

Another interesting technology is In-Cell touch technology. In In-Cell, a layer in the touch sensor is integrated with the LED display circuitry, making the sensor display sandwich one sensing layer thinner. The disadvantages of In-Cell is that the touch controller needs to be custom-built to work with the display circuitry, and such form factor is not practical on bigger displays because of latency issues. Also the sensor area can't be bigger than the display area. It looks like In-Cell will only be used in ultra-thin smart phones and will not be able to move to bigger form factors. Apple did not pick an In-Cell display for the iPad mini, but achieved a similar space savings by using a super thin film touch sensor instead of glass.

Conclusion

I believe all these new technologies in conjunction will replace ITO. Each one caters to a sector in the touch sensor market, except metal mesh, because it can be used in any size and form factor. The touch sensor market is big enough to fit all players; the only loser here will be ITO manufacturers. All companies in this article are in to gain big in the touch revolution.

Source: Touch Sensors: The Next Generation