Electrothermal Color Tuning of Cholesteric Liquid Crystals Using Interdigitated Electrode Patterns

A transparent color-tunable device is presented based on an electrothermal response by using interdigitated electrode patterns. The response is generated by applying an in-plane AC electric field that heats up a thermosensitive cholesteric liquid crystal mixture. The induced temperature elevations cause band gap shifting (Delta lambda > 350 nm) up until a colorless state is reached, corresponding to the isotropic phase. Color shifting can be tuned manually by varying the electric field or autonomously by the surrounding temperature. Broadband dielectric spectroscopy reveals that the electrothermal response originates from resistive heating of the transparent electrode pattern in conjunction with the cell capacitance and is therefore largely dependent on the electrode configuration. Hence, the electrothermal response can be easily modified by changing the electrode pattern, frequency and/or voltage, dependent on the user's requirements. Therefore, the ability of this technique to manipulate the autonomous thermal response by an electric field, using only one conductive substrate, shows promise in the field of optoelectronics, sensors, and smart windows.

Automated summary

This transparent color-tunable device utilizes an electrothermal response to induce color shifting, which can be manually or autonomously adjusted. Broadband dielectric spectroscopy reveals the mechanism behind the electrothermal response, allowing for flexible modification of the device's response by changing electrode patterns, frequencies, and voltages.