Grippers are an important part of robots. Often they are used in gripping and taking objects and play the most important role in robotic arms. Most of the grippers cost much money and may not be easily affordable by hobbyists. Then the best option is to build your own gripper.When it is from the so called ‘useless junk parts’, it becomes more interesting. So let us dive into more details.
In order to construct this gripper, all you need is the mechanism of on old CD/DVD player, some acrylic sheets or even some small wooden boards for the gripper, some screws and a little hot glue. The mechanism is shown below:
As seen from the above images, the CD/DVD player mechanism consistes of a rack and pinion arrangement to drive the eye across the disc and another stepper motor mechanism to drive the disc. It is driven using a simple DC motor and a pair of gears used to increase torque and decrease the speed of the motor, giving a fine control. Now we can cut and remove some parts of the mechanism, ie, the stepper motor section. Now it will look like this.
What we are left with is a mechanism shown above. It now consists of only the eye and the rack and pinion mechanism to drive it. Driving the motor causes the eye to move towards and away from the stationary part shown at the bottom of the above picture. Now if we replace the eye with something else (preferably something that looks like a robotic gripper), we end up with a partially functional robotic arm. I think you got the logic behind this, and thats all now use your imagination to work out better… The images of my first working prototype are given below
I also added an Infrared LED and its sensor to the tips of my robotic gripper to detect whether an object is present in between the gripper and it worked pretty nice.
Achu's TechBlog 
I liked your article is an interesting technology
thanks to google I found you