A novel wireless inkjet-printed chipless sensor for moisture detection utilizing carbon nanotube

A new chipless sensor for water droplet detection is proposed. This concept is demonstrated by inkjet-printing a dual rhombic loop scatterer on a flexible substrate having a size of 4×2cm² only. This sensor operates in the ISM band at 2.45 GHz. The scatterer is doped with a thin layer of carbon nanotube-based organic ink to enhance its sensitivity in the presence of water. Strong water molecule adsorption by the carbon nanotubes helps to detect and record when a water drop has been in contact with the sensor. The sensor´s electromagnetic response is modified permanently so that a “water event” can be detected later. Simulation and wireless measurement results validate this new concept.