Showing posts with label Hi-Tech. Show all posts
Showing posts with label Hi-Tech. Show all posts


Lab on a Chip: What is this?

This digiknol is really not for every one as this is high tech or miniaturization technology. But you have to acknowledge that every electronics and some other fields are based on this miniaturization.

Scientists dream, as other people do. However, they dream for the welfare and betterment of humanity as a whole. When dream has a deadline, it is called a goal. Lab-on-a-chip has become a future goal for the scientists and researchers.

Lab-on-a-Chip technology is a rapidly extending area of science with applications in biotechnology, clinical diagnostics, chemical analysis, and pharmaceutics.

Looking back at the history, we see that IBM launched the first computer with a hard disk drive (HDD) in 1956. The HDD weighed over 1000 kg and stored only 5MB of data. IBM needed an airplane at that time to transport that HDD storage device. Now we can place several GB data on our fingertip. The race of miniaturization started with the development of transistor and photolithography, and nowadays we have come to an era where scientists and engineers are trying to build a laboratory on a tiny chip.
The term “Lab-on-a-chip (LOC)” feels like an exaggeration, but it is a fact. LOC is a chip of only millimeters to a few square centimeters in size capable of performing several functions that are normally done in laboratory.
Hype was created with the introduction of the term LOC. Expectations started building up. It turned out to be the dream of scientists to fabricate fully functional laboratory on a small piece of substrate that may be a glass, Silicon or any polymer like PDMS. A normal chemical analysis laboratory has several functions to perform that include mixing, separation, identification, and storage of chemicals and interpretation of results.

A schematic of how laboratory functions are confined in a chip
When we go to a blood test laboratory, they take sample of our blood. Then, several functions are performed that make them able to deduce the results. Similarly, LOC also requires mixers, liquid flow channels, separators, storage wells, sensors, etc to complete the whole cycle from sampling to results. LOC is often called a subset of MEMS for good reasons because the components of a normal lab-on-a-chip like wells, mixers, micro pumps and a few others were borrowed from the MEMS technology. At the beginning of the 1990s, the LOC research started to seriously grow when the funding agencies realized the potential benefits hidden in these chips.

-How lab-on-a-chip is fabricated?

The root of the fabrication processes for LOC can be easily tracked down in the well-developed semiconductor fabrication technologies. The invention of photolithography gave a boost to miniaturization of devices back as far as in 80’s. The same photolithography is also being applied in the manufacturing of LOC. However, semiconductor technology is based on the Silicon that is not a material of interest as a substrate for performing biological test.

Attention was paid to Glass, PDMS and ceramics that have the properties desirable for LOC like specific optical characteristics, biocompatibility, and lower production costs. As rightly said that “necessity is the mother of invention”, engineers also developed new methods that were easily implementable with the materials like PDMS, glass etc. These methods include Hot embossing (or imprinting), injection molding, soft lithography etc. Details of these methods are out of the scope of this article. Therefore, summing up all these facts, we can say that fabrication process for LOC is a mixture of old and new techniques.

-Current status and future of LOC.

Currently, LOC is in active research phase. The total market for biochips was $2.4 billion in 2008, which rose to $2.6 billion in 2009. Expected market growth rate for biochips (LOC, DNA chip, Protein chip) in future is almost 17.7% to reach $5.9 billion by 2014, according to BCCresearch. Some prototypes have been demonstrated that are fully functional but manufacturing of LOC have not started yet on commercial basis. There are various challenges with the scaling down of traditional chemical principles. Mixing of two or more streams of fluids in micro size channels, and the signal to noise ratio (SNR) are the two major hurdles faced by the researcher in implementation of the technology to daily life. Nevertheless, the prospects are immense.

Successful implementation of the technology will enable us to have small cell-phone-size devices to carry out medical examinations like blood test, urine analysis and DNA analysis in real time. Nowadays, these tests take from hours to weeks from sampling to results. Even, the technology will enable us to wear laboratory in form of wristwatch to check our body functions and parameters in real time and free of cost.

LOC needs only Pico liters of sample for testing purpose. For the sake of comparison, a drop of water is millions time larger than the liquid required for LOC. Complete mixing of two such a small liquid is the biggest issue in LOC. is possible with the help of LOC. DNA analysis,

LOC may hold the key to the future of the in-vitro analysis. These devices could one day guide us to a pinhead-sized implant or skin-mounted device able to instantly figure out the presence of disease bacteria or biochemical agents, Effective Drug delivery, DNA analysis. Lab-on-a-chip technology may soon become an important part of global health improvements through the development of point of care (PoC) testing devices.
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How AMOLEDs and Super-AMOLEDs are Fabricated?

 How AMOLEDs and Super-AMOLEDs are Fabricated?

Well, how do you want me to justify this post?

I can go as deeper as you wish; In fact, I can write this post right from the core of clean room where everything is done regarding display panels fabrication taking benefits from my educational and research backgrounds. However, not every person reading this post is a tech guy. You might only be interested in seeing display rather than being curious about what is inside. However, I can bet seeing and praising a display is much better if you know at least something about how these displays are made. Apart from just general knowledge, it also helps to choose you a better display according to your needs.

So, in this post I am going to write how the AMOLED (active matrix OLED) are fabricated and  about differences in fabrication processes in AMOLED, and Super AMOLED display. 

The type of display your Smartphone has is typically described by an alphabet soup – LTPS, AMOLED, SLCD, Super AMOLED and TFT LCD all represent different technologies used in the production of display panels. Knowing what each type does, its benefits and drawbacks will help you understand just how good (or not) your phone is.


AMOLED is actually ACTIVE MATRIX ORGANIC LIGHT EMITTING DIODE. So, AMOLED is just an OLED screen with the matrix being in Active state. Alternatively, let me go one-step further. AMOLED is an LED screen but it’s an organic LED instead of inorganic.

An active matrix OLED display consists of a matrix of OLED pixels that initiate light upon electrical activation that have been stuck or integrated onto a thin film transistor (TFT) array by using solution-processing techniques. Thin film transistor (TFT) operates as a series of switches to control the current flowing to each individual pixel. 

The first step is to make the backplane or TFT that is essentially very much similar to semiconductor fabrication root if Si is used as semiconducting material.

Ultra high purity cleaning of the substrate is the first step towards fabrication of AMOLED display.
After cleaning, doped Si precursor and SiO2 inslulating layers are applied on the substrate. Presently the plasma enhanced chemical vapor deposition (PECVD) is the only viable technique for this purpose to be used in production lines.

One important thing is worth mentioning here that nowadays Si is being replaced by amorphous indium-gallium-zinc-oxide because of its merits over Si. Samsung SDI’s development of a 12.1″ WXGA AMOLED highlighted the potential of this technology. The company used amorphous indium-gallium-zinc-oxide (a-IGZO) to replace silicon as the semiconducting layer of the TFT backplane.

Subsequently, Photolithography to define patterns, etching to create aspect ratios and doping to create transistors is done similar to traditional IC fabrications process. For AMOLED display, at least two transistors are needed for every pixel.

Afterwards, ITO (Indium tin oxide) which is a transparent material, is sputtered onto the TFT arrays that connects these arrays to the “outside world”.

Another cleaning step followed by buffer layer deposition by spin coating or solution processing makesthe backplane ready for further steps.

Next is the application of organic layers on the backplane. Light emitting polymers LEPs are used for this purpose. These can be applied by using spin coating or simple printing techniques also do the trick.
After application of organic layers, it’s time to make cathode and subsequent steps to finish the processing. Usually, if compared to LCD production, this stage starts from a thin calcium layer an Aluminuim foil to enhance conductivity and to act as a cathode.

AMOLED fabrication is complete upto this point. Its time to make the screen touch sensitive and to protect it from the atmosphere. 

A touch sensing glass panels is used if the display is intended as a touch screen display. Then the final transparent layer is applied to protect the AMOLED.

After encapsulation of the organic film is complete, the panels can be taken out of the clean room and packaging can be carried on for shipment.
AMOLED (Lower) Vs Super AMOLED (Upper)

Because of the fabrication process, AMOLED can be difficult to view in direct sunlight. AMOLED panels are typically three layers, the AMOLEDs, the touch-panel sensor layer made of glass and then the top glass protective surface with air in between each layer. The diffusion of light through all three layers causes the AMOLED light to be diffused and difficult to see.

Note that no anti reflecting layer is used in the fabrication of AMOLED panels that generated the biggest criticism for this display --- LOW VISIBILITY IN DIRECT SUNLIGHT.


So how to make the display crispy in direct sunlight? Simple. Make it super-AMOLED guys.

Samsung came up with a new strategy. The problem was the number of layers once the AMOLED fabrication part is complete. Samsung joined the touch sensitive layer and the top protective layer in one single layer that helped to eliminate the gap and air between those two layers. By reducing the number of layers and removing one air gap, light dispersal is reduced, making these AMOLED displays easier to see in bright light.

The “Active matrix” describes how each OLED is addressed or controlled. The alternative is a passive matrix display where rows or columns of OLEDs are addressed rather than individual pixels. As a result, AMOLED displays are not only brighter, use less power, they are also faster.

The Samsung i9000 Galaxy S series, including the Captivate, Epic 4G, Fascinate, and Vibrant, the Windows Phone 7 Omnia 7 ,  Nexus S and Focus along with many other phones uses super AMOLED display.

The following Promotional video from Samsung depicts the difference in AMOLED and super AMOLED display.


Polymer Light-Emitting Diodes (PLED): A Promising Display Technology of the Near Future

HPolymer light-emitting diodes (PLED) that uses  light-emitting polymers (LEP) are the next generation display types that promise excellent results as well as cost and power efficiency. Moreover, PLEDs are very easy to fabricate a large area panel that facilitates the production of large display devices like TVs. Acording to PLED has shown their vision in taking LED technology to a new level.

Display industry is evolving at a very high rate. Researchers and Engineers are the backbones of this industry that are actively giving new ideas for future display industry. The most common types of displays include CRT, LED OLED, AMOLED, S-LCD, and Super-AMOLED etc. Super AMOLED is currently in very much active phase and Samsung as well as some other companies are shifting their products Display paradigm towards super AMOLEED screens. However, it is not easy to produce Super AMOLED display panels. Manufacturers, keeping in view the trends of industry and users, always focus alternatives.

Some Technical details of PLEDs
The story began in the Cavendish Laboratory of Cambridge University in 1989, when it was discovered that 'organic' LEDs could be fabricated using conjugated polymers.

Philips Engineer with 13'' Prototype polyLED TV.
Polymer light-emitting diodes (PLED) or light-emitting polymers (LEP), involve an electroluminescent conductive polymer that gives off light when attached to an external voltage. They are used as a thin film for full-spectrum color displays. Polymer OLEDs are quite efficient and require a relatively small amount of power for lighting. Polymers can be processed in solution, and spin coating is a simple method of depositing thin polymer films. This method is more suited to forming large-area films. Classifiable polymers employed in PLED displays include derivatives of poly(p-phenylene vinylene) and polyfluorene. Whereas, Substitution of side chains onto the polymer backbone may determine the color of emitted light or the stability and solubility of the polymer for performance and ease of processing.

Schematic illustration of a polymer light emitting diode (PLED). Philips themselves predicted that PLED-based TVs and computer displays will be on the market by the 2011.

So we can say that, in comparison with OLED, PLEDs have relatively simple structure, with the light-emitting polymer (LEP) layer combines the host, emitter and charge transport affairs in a single solution-processed film of the device. 

 According to Cambridge Display technologies:
One of the most electrifying developments in the display industry in the last 15 years has been the discovery and development of polymer light emitting diodes (P-OLEDs).
Littelfuse and Sigmaalgrich are already providing materials and substrates for Research of PLED.

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