In the Ropas project VTT has developed printed humidity sensors on paper substrate. The goal has been to tailor the humidity sensor performance to be suitable for consumer product use such as on package labels. Printed sensors are thin and flexible, because they are directly printed on paper or plastic substrates. When printed on paper substrate disposability or recyclability is achieved thus making them environmental friendly products. The use of printing technologies also provides cost-effectiveness, because of the use of inexpensive materials, low material consumption and mass-scale fast manufacturing processes.