The chalk board duster which is used by teachers to wipe the chalkboard seems very agonizing for them. What new mechanical/electronic devices can be devised to replace conventional chalkboard duster which can be easily operated by teachers. Please suggest product design approach for such new cleaning device. Thanks ps: I am not allowed to replace chalkboard to whiteboard
There are already comercial products like this. They exist primarily in the asian market. They usually consist of a vertical machine which moves along a rail at the top and bottom of the board. There are two common approaches:
The water approach is what most would be familliar with. It has been used for ages with the usual handheld sponge. What you need here is basicly a big vertical sponge (or multiple small ones) and a way to provide water. This can be done easily by use of a hose and/or letting the water drip through the sponge. Behind the sponge unit should be a way to remove the water like a squeegee. You can either make the robot only work in one direction or you need to have two squeegee with only one deployed at a time.
The vacuum method is less common and louder but doesn't need any water to function. It is not just like sucking air from the board. Instead there will be a moving belt to collect the chalk and a vacuum to remove it from the belt. There are also handheld versions of this. Keep in mind that this dry method can create the problem of dust to be contained. So this will certainly be harder.
In conclusion I belive the Water method would be easiest for a prototype. However in real classrooms the problem of stagnant water can quickly become a problem. A drying function could help here.
I would also reccomend reading this paper which seems to be very similar to you task.