| dc.description.abstract | Disruptive Technologies(DT) has a sensor that is able to measure touch and proximity by monitoring change in capacitance. This work investigates the possibility of using the sensor for Relative humidity(RH) measurements. This is realized by attaching a Kapton Polyimide(KP) film on top of the sensor, which changes its dielectric constant in changing humidity, which has a direct impact on capacitor size. A copper film is also attached to the top of the KP film to get better sensitivity. This work focus on making a theoretical model of the sensor in Comsol Multiphysics(CM). In CM theoretical simulations are done to check if the sensor works best in touch mode or proximity mode, if it works best with or without copper film, and the influence of KP thickness. Experiments were also executed to confirm that the simulation results were reasonable. The simulation and experiment results show that, when using KP as the sensing material the DT sensor benefits from having a copper film on top. The simulations showed that the DT sensor has an average sensitivity of 1.78fF/%RH from 0-100%RH, and the lowest change is 1.64fF/%RH from 75-100%RH with a 50 µm KP film, a copper film, and with the sensor in proximity mode. The measurements from the DT sensor are presented in a graph which increases in steps of about 0.5fF. So even the lowest increase of 1.64fF/%RH gives at least three steps increase for each percentage increase in RH. This indicates that the sensor could be used for RH measurements with the presented solution. The simulations also showed that a thicker KP film gave significantly better sensitivity with increasing thickness up to 75 µm KP thickness. Above this thickness the increase dwindled. The experiments was executed with different parameters than the simulation results above (for practical reasons). New simulations were executed with the same parameters as in the experiments which gave similar results as the experiments. This indicates that the simulation model gives decent estimated results. The experiments with a 50.8 µm KP film, and with a copper film on top, gave a change of about 51.7fF between 25%-95% RH. This gives an average sensitivity of 0.74fF/%RH between 25%-95%RH. The response time in the experiment between 25%-95% RH is over 50 hours with a 50.8 µm KP film. This limits the areas where the sensor can be useful, but this response time can probably be drastically reduced with better perforation techniques on the top electrode. | en |
