PLASTIC MEMORY INTRODUCTION :
Imagine a scenario where the memory stored in your digital camera or personal digital assistant is partially based one of the most flexible materials made by man: plastic.
Scientists at HP Labs and Princeton University are excited a new memory technology that could store more data and cost less than traditional silicon-based chips for mobile devices such as handheld computers, cell phones and MP3 players.
A conducting plastic has been used to create a new memory technology with the potential to store a megabit of data in a millimetre-square device - 10 times denser than current magnetic memories. The device should also be cheap and fast, but cannot be rewritten, so would only be suitable for permanent storage.
The device sandwiches a blob of a conducting polymer called PEDOT (POLYETHYLENE DIOXYTHIOPENE) and a silicon diode between two perpendicular wires. Substantial research effort has focused on polymer-based transistors, which could form cheap, flexible circuits, but polymer-based memory has received relatively little attention.
The beauty of the device is that it combines the best of silicon technology - diodes - with the capability to form a fuse, which does not exist in silicon," says Vladimir Bulovic, who works on organic electronics at the Massachusetts Institute of Technology.
However, turning the polymer INTO an insulator involves a permanent chemical change, meaning the memory can only be written to once. Its creators say this makes it ideal for archiving images and other data directly from a digital camera, cellphone or PDA, like an electronic version of film negatives.
INTRODUCTION OF PEDOT:
PEDOT's ability to conduct electricity means it is already used widely as the anti-static coating on camera film. But until now, no one suspected that it could be converted into an insulator.
The material is a blend of a negatively-charged polymer called PSS-and a positively-charged one called PEDT+. Having distinct, charged components allows it to conduct electricity and means that it is water soluble.
The team is not sure why it stops conducting when high currents pass through. But Princeton researcher Stephen Forrest suspects that the heat produced by a high current gives the PSS- layer sufficient energy to snatch a positively-charged hydrogen ion from any water that has dissolved on its surface, forming a neutral PSSH.
Without the negatively-charged PSS- to stabilise it, PED+ in turn grabs on to an extra electron and also becomes neutral, converting PEDOT into an insulating polymer.
Flash memory (sometimes called "flash RAM") is a type of constantly-powered nonvolatile memory that can be erased and reprogrammed in units of memory called blocks. It is a variation of electrically erasable programmable read-only memory (EEPROM) which, unlike flash memory, is erased and rewritten at the byte level, which is slower than flash memory updating. Flash memory is often used to hold control code such as the basic input/output system (BIOS) in a personal computer. When BIOS needs to be changed (rewritten), the flash memory can be written to in block (rather than byte) sizes, making it easy to update. On the other hand, flash memory is not useful as random access memory (RAM) because RAM needs to be addressable at the byte (not the block) level.
An EEPROM (also called an E2PROM) or Electrically Erasable Programmable Read-Only Memory, is a non-volatile storage chip used in computers and other devices to store small amounts of volatile (configuration) data. When larger amounts of more static data are to be stored (such as in USB flash drives) other memory types like flash memory are more economic. SEEPROM, meaning Serial EEPROM, is an EEPROM chip that uses a serial interface to the circuit board.
BASIC PROPERTY OF PLASTIC:
While experimenting with a polymer material known as PEDOT, Princeton University researcher Sven Moller determined that although the plastic conducts electricity at low voltages, it permanently loses its conductivity when exposed to higher voltages. Together with colleagues from Hewlett-Packard Laboratories, he developed a method to take advantage of this property to store digital information, which can be stored as collections of ones and zeros
The PEDOT-based memory card consists of a grid of circuits comprising polymer fuses. A large applied current causes specific fuses to "blow," leaving a mix of functioning and nonfunctioning connections. When a lower current is later used to read the data, a blown fuse blocks current flow and is read as a zero, whereas a working fuse is interpreted as a one. Because the storage method involves a physical change to the device, it is a so-called WORM--write once, read many times--technology. "The device could probably be made cheaply enough that one-time use would be the best way to go," says study co-author Stephen Forrest of Princeton University.
The team predicts that one million bits of information could fit into a square millimeter of material the thickness of a sheet of paper. A block just a cubic centimeter in size could contain as many as 1,000 high-quality digital images, the scientists suggest, and producing it wouldn't require high-temperatures or vacuum chambers.
formula of the plastic polymer, PEDOT. .
Â¢ Fig 1A) Write - Read -Erase cycle. A -6V pulse is applied to bring the memory in its written
applied to erase to
state. Subsequently the memory is read at -0.5V. A two-terminal device in which an organic Further a +6V pulse is
semiconducting polymer is sandwiched
between two electrodes, indium doped tin memory. oxide (ITO) and aluminum. The Â¢ Fig 1B) A schematic experimental devices contain two polymer overview of a memory cell layers. The first layer consist of PEDOT:PSS to which an inorganic salt (e.g. lithium triflate) and plasticizer (ethylene carbonate, EC) have been added. The second layer consists of poly(3-hexylthiophene) (P3HT) doped with the plasticizer. Motion of the ions present in the device under influence of an electric field is expected to induce switching between a high and a low conduction state, the so called ON and OFF state of a memory device.
COMPARISION WITH FLASH MEMORY:
#1 - Plastic memory is fast. Lab-built devices with a 1GB storage capacity have yielded read/write cycle times that are 10 times faster than CompactFlash, which are typically 2-10MB/s read, 1-4MB/s write.
#2 - It requires far fewer transistors, typically only 0.5M (million) for 1GB of storage (!!) compared to silicon's 1.5-6.5B (billion).
#3 - It costs about 5% as much to manufacture compared to silicon-based memory.
#4 - It can be stacked vertically in a product, yielding 3D space usage; silicon chips can only be set beside each other.
#5 - It has very low power consumption.
#6 - The control circuitry only occupies 1-5% of total transistor area.
#7 - It maintains memory even when the power is turned off. Nothing new compared to flash, but worth mentioning.
1) One million bits of information could fit into a square millimeter of material the thickness of a sheet of paper. A block just a cubic centimeter in size could contain as many as 1,000 high-quality digital images.
2) Technology could potentially store more data than flash, and perhaps even become fast enough to store video.
3)Scientists suggest, and producing it wouldn't require high-temperatures or vacuum chambers.
4)Unlike a CD, reading data stored on this memory block does not involve any moving parts or a laser. Instead it can be plugged directly into a circuit.
5)It's a very cheap technology which gives it a upper hand over other technology.
6)A PEDOT-based machine could solve the problem of virus hackers, who rely on the fact they cannot afford to leave a trace out of fear of being caught for their dirty work. With PEDOT-based solutions, Jackson and Perlov said hackers would not be able to erase their IP addresses.
1) It can be read many times but it can be write only ones.
2) The biggest challenge is developing production technique.
3) This technology is still under research, so it will take about 5yrs to launch in the market.
COMPANIES INVOLVED IN THE RESEARCH OF THIS