Wide range highly sensitive relative humidity sensor based on series combination of MoS2 and PEDOT:PSS sensors array

Abstract In this work, a polymeric material poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and a two dimensional material molybdenum disulfide (MoS 2 ) 2D nanoflakes have been employed as the active layers of two separate transducers on a single substrate for the detection of relative humidity. The portion with MoS 2 based active region showed high responsivity towards low humidity levels while PEDOT:PSS based portion responded well to high humidity levels. These two sensing portions were connected in a series combination to fabricate a single humidity sensing device capable to respond to a wide range of relative humidity with very high sensitivity. 2D MoS 2 nanoflakes were obtained by aqueous exfoliation of pristine MoS 2 . The transducer electrode pairs were fabricated using reverse offset printing technique on a piezoelectric LiNbO 3 substrate. The active thin film of MoS 2 flakes was deposited by Electrohydrodynamic atomization (EHDA) while the thin film of PEDOT:PSS was deposited by SAW-EHDA hybrid system. The fabricated sensor is capable of sensing relative humidity with high sensitivity (50 kΩ/%RH or 800 Hz/%RH) in a wide range of 0% RH to 80% RH. The response and recovery times are also excellent with values of 0.5 s and 0.8 s respectively. This unique approach of combining multiple transducers in a single sensing device can lead to the development of high performance sensors and can solve the current limitations of single transducer based sensing devices.