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Ultrasonic Liquid Crystal Light Diffuser Offers Dynamic Control

In a study published in the journal Scientific Reports, researchers from Doshisha University developed a unique tunable ultrasonic liquid crystal light diffuser that allows for directional changes in diffusion.

Ultrasonic Liquid Crystal Light Diffuser Offers Dynamic Control

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Light is indispensable to human life, and since the discovery of fire, various artificial light sources such as incandescent lamps, gaslights, discharge lamps, and light-emitting diodes (LEDs) have been developed.

The distribution and intensity of indoor artificial light are crucial for effective study and work and significantly impact our physical and mental health. Consequently, modern artificial light sources are designed considering these psychological aspects to achieve optimal aesthetics.

LEDs, the latest innovation in artificial lighting, are highly efficient and contribute to environmentally friendly lighting systems. However, due to their smaller size compared to traditional light sources, LEDs require diffusers to spread light over a larger area.

Traditional light diffusers feature periodic surface profiles, periodic refractive index distributions, or light-scattering layers to direct and spread light in specific directions. These optical characteristics are customized during fabrication to meet specific needs.

However, once fabricated, properties such as diffusion directivity, or the direction of transmitted light distribution, cannot be altered. Controlling diffusion directivity post-installation typically involves mechanically moving optical components, which can increase the device's size. Therefore, diffusers that allow control of diffusion directivity without mechanical parts are rare.

In a recent study, Professor Daisuke Koyama and graduate students Mr. Yuma Kuroda and Mr. Ryoya Mizuno from the Faculty of Science and Engineering at Doshisha University introduced an innovative tunable ultrasonic liquid crystal (LC) light diffuser.

Our ultrasonic LC light diffuser is based on the generation of non-coaxial resonant flexural vibration, which controls the molecular orientation and refractive-index distribution of the LC layer, providing control over diffusion angle and direction. It has a thin and simple structure with no mechanical moving parts.

Daisuke Koyama, Professor, Faculty of Science and Engineering, Doshisha University

The ultrasonic liquid crystal (LC) diffuser features a nematic LC layer sandwiched between two glass discs, with an ultrasonic piezoelectric transducer embedded in the device.

The transducer's electrodes are arranged in a circular pattern within the diffuser. When a continuous reverse-phased sinusoidal signal is applied to the transducer, it generates ultrasonic vibrations on the glass discs. If the vibration frequency aligns with the resonant frequency of the LC diffuser, various non-coaxial resonant flexural or bending vibration modes are created in the LC layer.

These vibrations cause variations in acoustic energy among the LC layers, glass discs, and surrounding air, leading to an acoustic radiation force at the boundary between the LC layer and the glass discs. This force modifies the molecular orientation of the LC layers, thereby changing the light distribution. By adjusting the electrodes receiving the input voltage, the direction of molecular orientation and, consequently, the light diffusion direction can be easily controlled.

Light diffusers that allow control over diffusion directivity can reduce energy consumption and enable users to tune the light distribution to their taste, resulting in better aesthetics Our device marks the first report of an ultrasonically controllable optical diffuser based on LC material, providing users control over diffusion directivity within a small space.

Daisuke Koyama, Professor, Faculty of Science and Engineering, Doshisha University

This device holds significant potential to transform indoor lighting, offering enhanced and customizable aesthetics through its ability to control light diffusion.

Journal Reference:

Kuroda, Y., et al. (2024) Ultrasonic liquid crystal tunable light diffuser. Scientific Reports. doi.org/10.1038/s41598-024-66413-2.

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