Touch screens are heading for the market mainstream boosted by the huge success of the iPhone, experts report.

Analyst firm iSuppli said that global shipment revenues for the leading touch-screen technologies will rise to $4.4bn by 2012, up from $2.4bn in 2006.

"Catalysed by Apple's iPhone, sales of touch screens using projected-capacitive technology are growing dramatically," said Jennifer Colegrove, senior analyst for emerging displays at iSuppli.

"Projected-capacitive touch screen technology is more durable and has better transmittance than the more commonly used resistive technology.

"More touch-screen manufacturers are developing and commercialising this type of screen, and the average price gap between capacitive and resistive displays is dwindling."

Colegrove explained that, since the iPhone proved that multi-touch technology can be portable and affordable, multi-touch has become the "hot topic" in the industry.

Many providers of alternative touch-screen technologies have announced multi-touch capabilities, such as the optical imaging camera-based touch screens offered by NextWindow.

Other examples include IR Touch Systems Technology's infrared touch screen, and Stantum's multi-touch music controller.

According to iSuppli, resistive is the most commonly used touch screen technology in the marketplace.

Although it is not very durable and has poor transmission qualities, resistive's low price and responsiveness to finger and stylus touch has made it the number one touch screen technology in terms of unit shipments during the past few years.

However, iSuppli noted that the resistive market is suffering a shortage of Indium Tin Oxide (ITO) film used to make such screens due to production expansions among several major manufacturers and limited numbers of ITO film suppliers.

With several large manufacturers expanding capacity, other types of transparent conductive materials such as conductive polymer, carbon nanotube and Antimony Tin Oxide now have an entry opportunity.

Fujitsu already has already started using conductive polymer for some of its resistive-type touch screens.

In addition tactile feedback technology is finding usage in increasing numbers of touch-screen devices. The technology delivers a sensation similar to that of pressing a physical button.

The analyst firm predicts that technological variations being commercialised on mobile phones in 2008 and 2009 include sensor-in-pixel or in-cell touch, bending wave from Elo/Tyco Electronics and polymer waveguide from RPO.