Multitouch is a technology that is capable of detecting one or more touches (typically via a finger) and movements on a surface simultaneously. A gesture is a series of touches recognized as a pattern and registered as a single event. The reading and interpretation of touches is a task an ambitious developer can tackle, but luckily, platforms are increasingly doing the job for us.
How Does It Work?
The number of touch screen manufacturers is growing rapidly and their engineers are constantly researching new and improved ways to detect touches. The technology is a combination of ingenious hardware and clever software.
Resistive technology requires two flexible sheets, electrically conductive, with vertical and horizontal lines for precision location. The sheets are separated by an air gap or microdots. When pressed firmly, they make contact and a change in the electrical current is registered and sent to a controller. This technology is very accurate and fairly inexpensive, but it does not support multitouch and does not work well with gestures.
Capacitive technology uses a surface made of insulator-like glass, also called a ground plane, and coated with a transparent conductor. Voltage is applied to the surface. The finger works as the capacitor that modifies the surface’s electrostatic field—more specifically, the coupling between row and column electrodes. The controller can determine
the location of the touch from the change in capacitance as measured from the four corners of the surface. This technology is durable and accurate, except when the screen is small or the user is wearing gloves, and it is used in many modern PDAs, such as the iPhone and Android-based devices.
Other technologies, used in nonmobile devices or equipment in a controlled environment, include infrared, acoustic digitizer, and in-cell.