What is Liquid Crystal?
Liquid crystal is a type of matter that exists in a state between a liquid and a solid crystal. It has some properties of both liquids and crystals.
Like a liquid, a liquid crystal can flow and take on the shape of its container. However, unlike a liquid, the molecules in a liquid crystal are arranged in a specific ordered pattern. This ordered arrangement gives liquid crystals some of the properties of a solid crystal, such as a definite shape, an optical anisotropy, and a lack of translational symmetry.
The liquid crystal molecules are typically rod-like or disc-like in shape, and they tend to align themselves in a particular direction when placed under an electric field. This alignment is what gives liquid crystals their unique optical properties, such as the ability to change the polarization or color of light passing through them.
There are different types of liquid crystals, such as the nematic, cholesteric, smectic, and polymeric liquid crystals, and each one has different properties and structures.
What “Normally Open Liquid Crystal” means?
A normally open liquid crystal is a type of liquid crystal cell in which the liquid crystal molecules are oriented in a way that allows light to pass through when there is no voltage applied to the cell. This means that the cell is in its "open" state and does not block light. Normally open liquid crystal cells are used in applications where it is important that a transparent mode will be when no voltage applied such as sun glasses, ski goggles, AR glasses and more.
What “Normally Open Guest Host Liquid Crystal” means?
Normally open guest host liquid crystal refers to a type of liquid crystal mixture in which the guest molecules, typically dyes or pigments, are dispersed within a host liquid crystal matrix. In this type of mixture, the guest molecules are not strongly interacting with the host molecules and as a result, the guest molecules are free to move around within the host matrix. This results in the liquid crystal mixture having a "normally open" or "transparent" state, meaning that light can easily pass through the mixture when it is in its non-active state.
A chiral dopant, also known as a chiral agent, is a type of molecule that is added to a liquid crystal mixture in order to introduce a chiral (or "handedness") property to the liquid crystal. The addition of a small amount of chiral dopant can cause the liquid crystal molecules to align in a specific way, forming a chiral nematic or cholesteric liquid crystal structure.
The chiral dopant molecules interact with the liquid crystal molecules and cause them to align with a specific handedness, creating a helical twisting of the liquid crystal molecules around a central axis. This helical structure is responsible for the selective reflection of certain wavelengths of light.
Chiral dopants are used to create a wide range of liquid crystal structures and are used in a variety of wearable devices applications.
What Cholesteric Liquid Crystal means?
A cholesteric liquid crystal (CLC) is a type of liquid crystal that has a specific type of helical structure. The long-range order of the cholesteric liquid crystal is characterized by a helical twisting of the liquid crystal molecules around a central axis, which is known as the helical axis. This helical structure causes the liquid crystal to exhibit a phenomenon known as selective reflection, where certain wavelengths of light are reflected while others are transmitted. This results in the liquid crystal having a characteristic iridescent or rainbow-like color, which is known as the "cholesteric color." CLCs are also known as "chiral nematic" liquid crystals and are used in a wide range of applications such as in displays and optical filters.
What should I imagine when thinking of a Cholesteric Guest Host Liquid Crystal?
You can visualize a mixture of small guest molecules, such as dyes or pigments, dispersed within a host matrix of liquid crystal molecules. The guest molecules are not strongly interacting with the host molecules, and as a result, they are free to move around within the host matrix.
The host liquid crystal molecules are arranged in a specific helical structure, known as a cholesteric structure. This helical structure causes the liquid crystal to exhibit selective reflection, where certain wavelengths of light are reflected while others are transmitted. The guest molecules are also aligned with the host molecules, and as a result, they also exhibit selective reflection.
As a result of this selective reflection, the cholesteric guest host liquid crystal appears to have a characteristic iridescent or rainbow-like color, which is known as the "cholesteric color." The guest molecules also give the cholesteric liquid crystal different colors, depending on the type of guest molecules.