A multimodal impedimetric sensor for humidity and mechanical pressure using a nanosized SnO₂-Mn₃O₄ mixed oxide

The authors describe a sensor based on the deposition of the binary oxide SnO₂-Mn₃O₄ between copper electrodes fixed on a glass substrate. The impedance of the sensor is shown to strongly depend on relative humidity (RH) and mechanical pressure. A silicone adhesive was added to the binary oxide nanomaterials and investigated with respect to its effect on the sensing performance. The impedance of the material decreases by a factor of 54.7 with increasing RH in the range of 10-90% in pristine SnO₂-Mn₃O₄ nanorods, but 29.6 times in SnO₂-Mn₃O₄ nanocomposites. Capacitance increases 390 times in pristine SnO₂-Mn₃O₄ and 26.6 times in SnO₂-Mn₃O₄ silicone nanocomposite at 100 Hz on going from 10 to 90% RH. Similarly, the impedance of the sensor also depends on mechanical pressure. The impedance of the material decreases by 80% on applying a mechanical pressure of 11.0 kN·m^-2, while capacitance increases by 70% at the same pressure. Graphical abstract A multimodal sensor was fabricated using SnO₂-Mn₃O₄ mixed oxide and its nanocomposite with silicon adhesive. The impedance of the material decreases while capacitance increases much more with increase in relative humidity and applying a mechanical pressure in SnO₂-Mn₃O₄ mixed oxide as compared to SnO₂-Mn₃O₄ nanocomposite.