Esnek Kapasitif Basınç Sensörlerinin Fabrikasyonu ve Elektriksel Karakterizasyonu

Abstract

In today's technological world, the growth of flexible electronic applications and their widespread adoption has significantly increased the importance of human-machine interaction and sensor applications. Flexible sensors that convert a physical or mechanical effect into an electrical signal output, and enable the interpretation of these outputs to serve desired purposes in technological applications such as health, robotics, wearable technology, education, and entertainment, hold an important place in flexible electronic applications due to factors like high flexibility, stability, high accuracy, ease of manufacturing, and low cost. Within the scope of this thesis, two different types of materials, namely Polydimethylsiloxane (PDMS) which stands out with its properties such as flexibility, adjustable hardness, heat resistance, biocompatibility, and Polyvinyl alcohol (PVA) and Borax mixture which have similar properties and also self-healing properties and hydrogel structure, were produced with different mixing ratios and different dielectric layer thicknesses without any additional micro and nano particle doping. The effects of both mixing ratio and dielectric layer thickness on sensor performance were investigated, and the two materials were compared. The produced sensors were subjected to electromechanical tests at various pressure values, and the effects of different materials, hardnesses, and thicknesses on sensor sensitivity and linearity in flexible capacitive pressure sensors were investigated. In addition, as a result of these studies, an 8×8 size capacitive sensor array was fabricated for the PVA and Borax mixture with the determined hardness value, and the sensor performance and its mapping according to the applied force on the sensor array are demonstrated. It has been observed that the parameters characterizing the sensor, such as sensitivity and linearity, of the PDMS-based sensor designs tested in this thesis vary with the mixing of the components that make up the material in different ratios and the use of varying thicknesses of the dielectric material. It was observed that the sensitivity and linearity were low due to the absence of any micro- and nano-particle doping in the PDMS. PDMS-based sensor designs exhibited sensitivity in the low-pressure range, and it was assessed that these sensor designs could be appropriate for use at low pressures. It has been observed that the parameters characterizing the sensor, such as sensitivity and linearity, of the PVA Boraxbased sensor designs tested within the scope of the thesis vary with the mixing of the components constituting the material in different ratios and the use of various thicknesses of the dielectric material. Additionally, it was noted that sensor performance was impacted by the weight loss of PVA Borax hydrogel over time. Although weight loss over time led to a decrease in peak capacitance values at the highest pressure in sensors with a PVA Borax dielectric layer, it was found that the material's transformation into a more rigid structure and the establishment of its stability positively influenced sensor performance. Compared to PDMS, it was observed that PVA-Borax hydrogel operates with higher sensitivity and linearity over a broader pressure range. Moreover, due to the self-healing property of PVA-Borax hydrogel, PVA-Borax sensor designs can be used for a long time. Producing PVA-Borax hydrogel requires less cost, effort, and ease compared to producing PDMS material. With this advantage, it is evident that PVABorax hydrogel possesses superior qualities compared to PDMS elastomer.