HOW A TOUCH SCREEN WORKS

There are mainly 2 types of touch screens that are widely used:

1. Resisitive touch screen

2. Capacitive touch screen

1.Resistive touch screen:
      Before going into the details of how it works, I wish to say what are its applications first so that we can better understand the topic

Applications:

        There are many applications of resistive touch screens some of them include

a) touch screens that we see in ATM's

b) touch screens used in supermarkets and malls

c) old touch mobile phones

 I quoted examples explaining the underlying concept just because this is what I expected in my school and college days from faculty so that I can have some interest in understanding what they are teaching.

Working principle:

The resistive touch screen consists of two transparent layers of glass or plastic that are coated with a conducting material like Indium Tin Oxide (ITO) and the coated sides of glass are arranged facing each other with a gap in between them

    When ever we apply pressure on the top layer it bends and touches the bottom layer which will create some kind of electrical disturbance at the point where we apply pressure. The x and y coordinates of this point exactly can be determined by sensor     

Pros and cons:

1. Unlike delicate capacitive touch screens these are hard in nature 

2. Multiple touches can't be detected so we can't zoom in ATM screen

2.Capacitive touch screen:

     capacitive touch screens make use of our body behaving like a capacitor (any object which has the ability to store charge). In capacitive touch screens electrodes of opposite charges are arranged perpendicular to each other all through the screen called as sensor grid. This sensor grid is covered by glass on top and bottom 

At the meeting point of these electrodes electric field will be created automatically.  So whenever we touch the screen at any point our finger (capacitor) will observe certain amount of charge creating a voltage drop at that point whose coordinates are then detected by sensors.

Applications:
        Present generation touch mobiles, laptops and many other

Add on's:

 In resistive touch screen we need to push the top layer so that it touches the bottom layer and in this process the screen bends little. And since resistive touch screens doesn't require any capacitor to make a voltage difference, this type of screens can work with any object pushing top layer .But in case of capacitive type it needs a object which acts like a capacitor so whenever we touch our mobile screens with clothes or things which are not capacitors they will not function and hence we can't use our mobiles with gloves to our hands 

** content is limited to my knowledge and comments are most welcome