A novel conductive humidity sensor based on field ionization from carbon nanotubes

A novel, high efficiency detector for humidity is described, in which the multiwall nanotubes grown on the silicon substrates serve as anode and ITO film glass plate as cathode are separated and insulated by a glass insulator. Application of a positive bias to the multiwall nanotubes generates high electric field sufficient to field-ionize passing gas-phase atoms especially for water vapor. By monitoring the prebreakdown current, relative humidity can be determined. The sensitivity factor (I_75.8%/I_12%) is about 229.4. The recovery time from 53.4 to 6.8% RH for the humidity sensor is about 10 s.