But how if i use 2 arduino uno, one for the current source, and the other one for voltage measurement?
The the two must be powered by independent power supplies, that is you can't power them both from the same computer.
But i still have to ask, does the current must be constant for the measurement?
Yes, if you are doing this with just a voltage you must adjust it so the current is the same for each measurement. I am not sure what resistivity your wafers are going to have but you can calculate the approximate values of current and voltage if you make an estimate of the expected resistivity.
project for university, not industry purpose. So is ok if the result is not as accurate as the pro instrument used in lab
As it is a University project then it is important you quantify the errors in the final instrument.
Oddly enough in 1974 my final year project was an automated system for measurement of resistivity and Hall coefficient by the van der Pauw method. This is a four point probe arranged in a clover leaf pattern. This was in the days before micro controllers and the whole thing was done with TTL logic gates, which included driving relays to switch the voltage and current between the pins and mechanically lowering, raising and rotating of the specimen in a magnetic field.