FLEXIBLE OLED DISPLAY TECHNOLOGY FOR ELECTRO-OPTICAL STIMULATION

G U I D E D B Y , C E L I N E M A R Y S T U A R T P R E S E N T E D B Y , C H I N C H U T H O M A S

INTRODUCTION

OPTOGENETICS: using light simulation controls the excitation, inhibition or signaling pathways of genetically modified neural tissue.

Neurons are genetically modified using viral vector.

Cells expressing Channelrhodopsin-2(ChR2) are activated by blue light.

Cells expressing Halorhodopsin are silenced by yellow light.

Common approach done is to insert the exposed tip of fibre optic cable into the brain tissue of an animal model.

Newer approach replaces this fibre optic probe with small array of discrete light emitting diode(LED).

This approach eliminates the need for a permanent opening in the cranium.

One key limitation in this approach is the inability to turn on individual pixels and also high power consumption.

Hence a new concept is introduced “FLEXIBLE OLED COLOR DISPLAY”.

They can be used on thin biocompatible plastic substrate to selectively activate individual pixels.

OLED Organic light emitting diode.

They are coated glass plates.

Organic compounds used are hydrocarbons.

Fabricated on plastic substrate.

these glass plates are tightly sealed to provide protection from moisture and oxygen.

Plates are of thickness 1/1000th of human hair, providing capability to bend over a wide variety of degrees.

They doesn't produce heat when turned on.

OLED technology produces self-luminous displays that doesn't require backlighting and hence they are more power efficient.

OLED requires only less power, i.e. 2-10 v.

They use substances that emit RED,GREEN and BLUE or WHITE light.

FLAT PANEL DISPLAY TECHNOLOGY Active matrix, thin film

transistor(TFT) array technology.

Interconnection wires enables to turn on individual pixels.

32 by 32 discrete LED array requires 1024 interconnections.

32 by 32 TFT active matrix array requires only 64 interconnections.

They cause heating problems in tissues due to the simultaneous turning on of large number of LED’s.

FLEXIBLE OLED DISPLAY TECHNOLOGY FOR OPTOGENETICS

Discrete array LED consists of one LED per pixel.

Active matrix OLED displays consists of two TFT’s and one capacitor(2TIC) per OLED pixel.

OLED,TFT and pixel capacitor is integrated on the same substrate.

It emits bright light when a forward bias is applied between a transparent anode and reflecting cathode.

Conventional TFT-based flat panel OLED displays are produced on fragile and rigid glass substrate.

Fragile glass substrate is replaced by a flexible plastic substrate of 125 micrometer thickness.

Flexible OLED is very thin and transparent sheet of plastic.

Constructed by sequential layering and patterning Nano scale thin films on its surface.

EXPERIMENTAL DETAILS AND DEVICE FABRICATION

the light emitted should be bright enough to induce optical stimulation.

Blue light in the range 450-460nm is the optimum wavelength.

Fluorescent blue OLED device structures consists of injection, transport and blocking layers along with emission layer.

Cathode used is a reflective aluminum surface and anode is a transparent Indium Tin Oxide(ITO).

Emissive layer used is a single host doped with a blue fluorophore.

Electroluminescence (EL) optical spectra is obtained using Ocean optics HR4000 CG spectrometer.

Luminance versus voltage (L-V) curve was collected using a Newport optics 818-UV photodiode.

RESULTS AND DISCUSSION

High light intensity pulsed blue OLED development A minimum of 1mW/mm2 of instantaneous pulsed

irradiance at a wavelength of 450nm is required.

The intensity is 0.1mW/mm2 for bottom-emitting blue OLED at 7v DC bias condition.

Pulsing the supply voltage of OLED.

A thin 30 micro metre flexible metal foil is bonded to the back of reflective cathode.

From the figure the required 1mW/mm2 of instantaneous light intensity is achieved at 13v,at 20Hz pulse with a 10ms pulse width.

Flexible OLED display biocompatibility

Biocompatibility and long term in-vitro durability of flexible OLED display were evaluated.

Ability to grow immortalized epithelial cells on the surface of full TFT-process plastic flexible display substrate.

Blue OLED’s requires ETHANOL(EtOH) sterilization. That doesn't make any change in the optical characteristics.

Operating temperature at the surface of the blue optical emitters under 1mW/mm2 pulse mode should be compatible with the living brain tissue.

ADVANTAGES Paper like readability.

Thin, light form factor.

Twistable

DISADVANTAGES Very low refresh rate.

Very slow zoom.

Ghost images

APPLICATIONS SHELF LABEL

Price information can be updated

Requires no battery

Uses energy from RF wave

E-books

Smart card display

Flexible as normal credit cards

CONCLUSIONS Benefit to economy and simplify everyday life

More applications in future.

Additional modifications done to accelerate the marketing.