Development and Application of Biomass Hydrogel in Photonic Transistor Memory

This study synthesized copolymers using two biomass materials, starch and ι-carrageenan, with poly(acrylic acid) and utilized ethylene glycol as a solvent-based cross-linking agent to produce hydrogels. The hydrogels developed from starch or ι-carrageenan exhibited high extensibility and mechanical strength after absorbing water molecules from the environment and maturing. The Young’s modulus was approximately 0.03 and 0.04 GPa, with elongation exceeding 600%, and the water content remained stable at around 15% over time. Additionally, these hydrogels can be hydrolyzed and recycled to recreate elastomers with similar mechanical properties. By the incorporation of chlorophyll into the hydrogels made from the two biomass hydrogels, they were successfully used as memory layers in phototransistor memory. The hydrogel cross-linking involved the formation of covalent bonds between the hydroxy groups of the biomass materials and carboxylic acid groups of poly(acrylic acid), while the non-cross-linked parts interacted with chlorophyll through hydrogen bonding. The devices perform electrical writing by applying gate bias and optical erasure by exposing them to 455 nm blue light. Notably, the device made from starch-based hydrogel exhibits a high memory window (∼21.8 V) and long-term stability exceeding 104 s. In conclusion, this study successfully derived high-biomass-content hydrogels from biomass materials and applied them to optoelectronic devices, demonstrating the successful application of biomass materials in high-quality optoelectronic devices.