sensors....

how to make a paper sensor??or do you have a readymade one? or where can we find one?

And with these questions you expect an answer? Ok, lets see.......

Object to sense: (a sheet of) paper ? Sensor: a ruler Shop: Amazon

With this "sensor" you could "sense" the length and width. Height will probably be difficult with one sheet of paper :)

Now seriously, your question is far, far, far, far...(10x far)...far from clear. What do you want to measure, desribe your problem?

You want to measure the weight or the color of paper or do you want a sensor made of paper?