Application Of Liquid Crystal

By:Nawaraj Kumar Mahato

Pankaj VermaRavi Ranjan Mehta

Rizwan Ankur Mishra

Kyalumba KabambaVishal Thakur

Introduction

• Very Important in the study of Optics, Chemistry and Polymer Science.

• Friedrich Reinitzer, australian chemist studied about it first in 1888

• At present it is applied in many products in our society and has come in our daily Use.

Fourth Sate of Matter

What is Liquid Crystal?

• Substance that exibit a phase of matter that have properties between those of a convectional liquid, and those of a solid crystal.

• Hence it shows Anisotropy.

Electric Field Effect on LC

• Molecules Align in the same direction as the field.

Phases

Nematic Phase

• Molecules in this phase are long and rod-like in shape. They are free to move in space.

Chiral Nematic

• This phase is composed of nematic molecules in a helical structure about the layer normal.

• The distance that it takes for the molecules to complete one turn is called the pitch.

λ = n*p*cosθ

Smectic Phase

• This phase can be reached at lower temperatures than the nematic phase.

• Molecules align themselves in layers.(They are restricted to their plane.)

• More order and higher viscosity

Columnar Phase

• Characterized by its stacked columns of molecules.• Discovered in 1977 by Chandrasekhar

Twisted Nematic

• This is called the twisted nematic liquid crystal and the spacing between the planes change with temperature. The spacing is associated with the wavelengths of light.

Applications of Liquid Crystals

The World Of Liquid Crystal

Liquid Crystal Displays

Liquid crystal display (LCD) is a flat electronic display panel used as a visual display aid. It uses liquid crystals to create visual effects on screen. Liquid crystal is a state of matter between solids and liquids. LCDs do not generate light on their own but rely on sunlight or room light to generate images with help of liquid crystal.

How LCD Works

Advantages Of LCD• Brightness: Produces very bright images due to high peak intensity. Very

suitable for environments that are brightly lit.• Emissions: Produce considerably lower electric, magnetic and

electromagnetic fields than CRTs.• Geometric Distortion : Geometric distortion at the native resolutions.

Minor distortion can occur for other resolutions.• Power Consumption:Energy efficient. Consume less than 1/3 the power of a

comparable CRT. Consume less electricity than a CRT and produce little heat.

• Physical Aspects:Take up about 40% less desk space. LCDs are thin and compact.

• Screen Shape :Completely flat screen.

• Sharpness: At the native resolution, the image is perfectly sharp. Adjustments are required at all other resolutions which can result in measurable degradation to the image.

Liquid Crystal Thermometers

Liquid-crystal thermometers use liquid crystals that change color in response to temperature changes. Mixtures of liquid crystals are enclosed in separate partitions. Numbers on the partitions indicate temperatures according to the amount of heat present. Liquid-crystal thermometers include some indoor digital thermometers and fever thermometers, which are placed on the forehead.

Optical Imaging

• Optical Imaging is an emerging technology with great potential for improving disease prevention, diagnosis, and treatment in the medical office, at the bedside, or in the operating room

Optical Imaging

Helmets and Bullet-proof vests• Long-chained rigid polymers that orient parallel to each other, with

very strong inter-molecular interactions, strong enough to withstand

the impact of bullets.

Battery testing strips (used by DuraCell)

• Charge indicator for batteries. The principles for this application is similar to that used by liquid crystalline thermometers. Electrical current passing through the media generates heat. The change of relative orientation of the layers produce a color change.

Slugs and Snails (nature)

• Nature beat us to the punch in making use of liquid crystals. The mucus secreted by slugs behaves like liquid crystals. Its rod-shaped molecules align in varying degrees to control the viscosity of the mucus to adapt to different ground conditions.

• Liquid crystals can also be found in biological cell-membranes

Conclusion• We know today that many chemical compounds

can exist in the liquid crystal state, such as cholesteryl benzoate. Thanks to the scientists that worked so diligently toward understanding this phenomenon, the world can focus on ways to make this product useful in society. Over the last century many applications such as the detection of hot points in microcircuits, the findings of fractures or tumors in humans and the conversion of infared images have become accessible due to the understanding of pitch in a liquid crystal.

Thank You