How It Works: Technology of Touch Screen

Touch screen Technology has sparked the explosive growth of the mobile device market nowadays. It started not so long ago with PalmPilot where we can tap on the screen with a tiny stylus, or exercise our thumbs on a BlackBerry micro-keyboard.

Later on along came the iPhone and then everything changed. Suddenly, people were wiping their fingers across screens, pinching images and performing other stuff that had not previously been part of the smartphone interface.

Now we not only take touch input for granted, we expect to be able to use multitouch (using more than one finger on the screen at a time) and gestures as well. Thus, how it works basically?

Many routes to touch

There are many different touch technologies available to design engineers. According to touch industry expert there are 18 distinctly different touch technologies available. Some rely on visible or infrared light; some use sound waves and some use force sensors.

However it turns out, two of these technologies dominate the market and the two approaches have very distinct differences. One requires moving parts, while the other is solid state. One relies on electrical resistance to sense touches, while the other relies on electrical capacitance. One is analogue and the other is digital.


Traditional Touch Screen

The traditional touch screen technology is analogue resistive. Electrical resistance refers to how easily electricity can pass through a material. These panels work by detecting how much the resistance to current changes when a point is touched.

This process is accomplished by having two separate layers. Typically, the bottom layer is made of glass and the top layer is a plastic film. When you push down on the film, it makes contact with the glass and completes a circuit.

The glass and plastic film are each covered with a grid of electrical conductors. These can be fine metal wires, but more often they are made of a thin film of transparent conductor material. The electrodes on the two layers run at right angles to each other: parallel conductors run in one direction on the glass sheet and at right angles to those on the plastic film.

When you press down on the touch screen, contact is made between the grid on the glass and the grid on the film. The voltage of the circuit is measured, and the X and Y coordinates of the touch position is calculated based on the amount of resistance at the point of contact.


Solid-state Technology

Meanwhile, Solid-state technology is slightly different. It has no moving parts. Instead of being based on electrical resistance, it relies on electrical capacitance. This technology is also known as Pro-cap.

Pro-cap touch screens use two layers of conductors, separated by an insulator. When we touch the screen with our fingers, it steals a little of the charge from each layer of conductors at that point.

The electrical charge involved is tiny, which is why we don't feel any shock when we touch the screen, but this little change is enough to be measured. Because each conductor is checked separately, it is possible to identify multiple simultaneous touch points.


What's next for touch

Touch screen technology is a part of our daily lives now. From just as simple as playing music to controling the temperature of a house. Touchscreen technology has invaded and become a major part of our lives.

There are many different types of touchscreen technologies and each work in their own different ways but relatively they are similar in how they work. Can we benefit from touch screen technology and apply it to more pre-exisiting technology or will this touch screen technology lead to new inventions?