Development of Pectin Biopolymer based Thin Film Devices for Sensor and Energy Applications

Abstract

This work focuses on synthesizing biodegradable, transparent, flexible, low-cost materials for sensor and energy storage applications. There are several thin films made of metal, metal oxide, polymers, and composites of polymer/metal in the fabrication of devices for sensors and energy storage applications. Among these, metal ions crosslinked polymers are prevalent for their flexible and transparent properties. The challenging factor with these crosslinked polymers is their complex process and synthesizing cost. In this thesis, we have focused on using pectin biopolymer to fabricate sensor and energy storage devices. The pectin polymer was opted for its abundant and low-cost availability. In Chapter 1, the structure of pectin and its nature has been discussed. Pectin is a fundamental molecule found in plants, trees, and fruits. Pectin helps them to communicate information, carry water molecules, and provide strength. Pectin crosslinks with Ca2+ ions available in the plant cells and provides adhesion, communication, and structural rigidity to the plant. Similarly, in this thesis work, pectin is crosslinked with Ca2+ ions for improved structural stability. The pectin crosslinked with Ca2+ fabricates thin films for temperature sensors, which is discussed in Chapter 2. Pectin is used as a temperature sensor based on the thermo-reversible property. Pectin with Ca2+ induces an ionic current when subjected to an increase in temperature. The Ca2+ ions trapped between the pectin chain cause the ionic movement due to the opening of pectin chains on temperature variation. A Poly (Ethylene Glycol) (PEG) plasticizer was used to enhance the ionic movement in the pectin film. The PEG creates a complex networking structure in pectin by forming cross chains on the main chain. This forms the fibrillar structure within the composite film, enabling more ions to migrate. Hence, we could fabricate a temperature sensor with Ca2+ crosslinked pectin with PEG.The pectin film was observed to have charge-storing ability while the electric..