The emergence of MnFe2O4 nanosphere-based humidity sensor: a methodical investigation by scanning Kelvin probe and its deployment in multitudinous applications

Abstract

In this study, the ambient temperature humidity sensing properties of solvothermally synthesized MnFe₂O₄ (MFO) nanospheres on interconnected comb-like silver electrodes were studied systematically. The sensing results revealed that the resistance of MFO decreased as the relative humidity (RH) increased owing to negative RH sensing characteristics. The prepared spinel-structured MFO sensor exhibited a wide humidity detection range (11% to 85% – static method), low hysteresis (∼5%) between the adsorption and desorption curves, high sensitivity (1.930 MΩ/%RH) and excellent detection resolution (2% RH). A scanning Kelvin probe (SKP) system was used to investigate the influence of different percentages of RH conditions on the surface potential of the sensor. The results showed that humidity directly affected the material's work function (ϕ) and contact potential difference (CPD). Finally, the fabricated sensor was integrated and tested in real-time samples, such as baby diapers, finger humidity for contactless switches, sweat pads, human breath for breath analysis/monitoring, and skin for the detection and monitoring of moisture levels.