Among different heat-responsive polymers, hydroxypropyl cellulose (HPC) is biodegradable and is widely used in products that are harmless to the human body, such as food and pharmaceuticals. When the temperature of the hydrogel-type HPC increases, the hydrophilic bonds between the HPC molecules break, and the HPC molecules aggregate owing to the hydrophobic bonds. Therefore, light transmittance may vary because the aggregated HPC molecules scatter light. This study investigated the implementation of a display using the thermoreversible phase transition of HPC. Herein, a near-infrared (NIR) laser was irradiated only to a local area to control the surface temperature and enable the effective operation of the thermoreversible phase transition of HPC. For this, cesium tungsten oxide (CTO), which absorbs NIR light and generates heat, was mixed with the HPC hydrogel to improve the photothermal effect. Moreover, by additionally mixing carbon nanotubes (CNTs) with high thermal conductivity, the heat generated from the CTO is quickly transferred to the HPC hydrogel, and the heat of the HPC hydrogel is quickly cooled through the CNTs after stopping the NIR laser irradiation. The produced NIR-writing CTO-CNT-HPC (CCH) thermoresponsive display exhibited a fast thermoresponsive time. The CCH thermoresponsive display developed in this study can be applied in situations that require fast display response times, such as interactive advertising, property exhibitions, navigation systems for car, schedule information, event information, and public announcements.
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