Carbon nanotubes, orange dye, and graphene powder based multifunctional temperature, pressure, and displacement sensors

This work presents design, fabrication, and investigation of carbon nanotube (CNT), orange dye (OD), and graphene powder based multifunctional sensors. The output of the multifunctional sensors is observed as change in resistance and impedance values for an input change in temperature, pressure, and compressive displacement between the sensors electrodes. Using these sensors, temperature variation ranging from 30 to $$65^{\circ }\hbox {C}$$ , pressure 0 to 0.1 $$\hbox {kgf\,cm}^{-2}$$ and longitudinal compressive displacements of 0 to 110 $$\upmu \hbox {m}$$ are measured as change in resistance and impedance at two fixed frequencies, i.e., 100 Hz and 100 KHz. An increase in both resistance and impedance of the sensors is observed with increase in temperature. The temperature coefficients of the sensors having resistances $$\sim 470$$ $$\Upomega$$ and $$\sim 890$$ $$\Upomega$$ were $$1.0\%\,{}^{\circ }\hbox {C}^{-1}$$ and $$1.9\%\,{}^{\circ }\hbox {C}^{-1}$$ , respectively, when evaluated for temperatures ranging from 30 to $$65^{\circ }\hbox {C}$$ . For applied pressure 0 $$\hbox {kgf\,cm}^{-2}$$ to 0.1 $$\hbox {kgf\,cm}^{-2}$$ and displacement 0 to 110 $$\upmu \hbox {m}$$ the resistance of the multifunctional sensor decreases 1.3 to + 12.7 times (from 6730 $$\Upomega$$ to 5210 $$\Upomega$$ and 3410 $$\Upomega$$ to 269 $$\Upomega$$ ) and 3.18 to 7.53 times (2235 $$\Upomega$$ to 702 $$\Upomega$$ and 6787 $$\Upomega$$ to 901 $$\Upomega$$ ), respectively. With increased thickness of OD layer from 300 $$\upmu \hbox {m}$$ to 570 $$\upmu \hbox {m}$$ , the output resistance and impedance of the sensors as a function of temperature also increased, exhibiting the improved sensitivity, however, at the expense of decreased pressure and displacement response of the sensors. Therefore, the thickness of OD film can be used as a design parameter for a desired sensitivity value to cater a particular application. The proposed multifunctional sensor can be a good candidate to measure temperature, pressure, and displacement of an industrial unit, such as flex bonding head because it offers light weight, simpler design, low maintenance, and eventually low cost.