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Going Organic
UCLA Materials Scientist Uses Semi-Conducting Polymers
to Build Next Generation of Electronic Devices
By Christopher Sutton
For more than ten years, researchers in academia and industry have been trying to build electronic devices from semi-conducting polymers like plastic – using organic materials to create components that are more flexible, cheaper and easier to manufacture than their silicon counterparts.
Yang Yang, a materials science professor in the UCLA Henry Samueli School of Engineering and Applied Science, is one researcher whose work on organic transistors and printable conducting polymers has kept him on the front lines of this wide-ranging effort. Recently, his research has begun to bear fruit, resulting in a number of patents and a promising start-up Yang co-founded last year.
“I’m excited. I have never been personally involved in launching a start-up company, and the experience has been very valuable,” said Yang. “In fact it has given me good lessons about the ‘real-world’ dynamics of technology development, and I’ve been able to pass this experience to the students I teach.”
When he joined UCLA in 1997, Yang began working on an organic plastic light-emitting device, which would light up when he passed a current through it.
“But devices like that have existed for at least 15 years,” said Yang, “so I began to concentrate on organic electronic memory devices with low cost, non-volatile memory.”
A lot of memory. Yang’s organic memory devices, which he began to work on four years ago, can store far more memory than flash memory devices on the market today. Flash memory in a typical USB device has a writing speed in sub-milliseconds, or one thousandth of a second. Yang’s device operates in nanoseconds, easily ten thousand times faster than traditional flash memory. This means that a digital camera, for example, could take pictures ten thousand times more quickly.
“Our memory devices greatly increase the speed of data storage, making it possible for people to experience faster PDAs, cameras, even movie downloads, though they would still be limited by the speed of their Internet connection,” said Yang.
Yang builds his electronic devices with organic components that he fabricates using wet coating processes, such as a unique inkjet printing method that he invented. Patterns are transferred onto plastic substrates and printed just like newspapers are printed on a press, making Yang’s method an attractive alternative to the costlier manufacturing processes of silicon wafers in clean rooms.
“Lithography is used to produce silicon chips,” said Yang. “But lithography is expensive and with organic electronics, the lithography process is actually quite harmful to the materials used. Our process dissolves organic materials into a solvent that can be loaded into an inkjet printer, and printed to the plastic substrate to form a circuit or wire.”
Regular inkjet printing, while it provides the patterning capability for a polymer solution and is compatible with flexible substrates, produces polymer films composed of many small dots and pinholes, making them intrinsically non-uniform. Those pinholes prevent the fabrication of high-quality polymer electronic devices.
Yang’s revolutionary hybrid design combines an inkjet-printed layer with a uniform, spin-coated polymer layer. The uniform layer serves as a buffer to seal the pinholes, and the inkjet layer holds the desired pattern. The sandwich device structure is completed with a final electrode deposited on top. Any pattern can be designed on a computer and the specifications loaded directly to the printer, eliminating the need for a clean room.
In 2003, Yang teamed up with Walter Mosher, chairman and chief technology officer of health-care product-maker Precision Dynamics Corporation to establish ORFID, a company that has built its technology platform based on inventions made in Yang’s lab.
In the summer of 2004, UCLA’s Office of Intellectual Property Administration licensed two patents to ORFID, which derives its name from ‘organic radio frequency identification.’ The two patents relate to Yang’s hybrid inkjet printing technology and to the devices created from the printing method.
Yang serves as Chairman of ORFID’s Science and Engineering Advisory Board, and sits on the company’s board of directors.
Organic electronics hold several advantages over silicon-based technologies, including greater versatility – organic electronics are flexible, meaning they can be built into a greater array of products.
Yang offered one scenario to explain how flexibility can lead to some novel uses: “Being a parent, one thing I always worry about when I take my son to theme parks like Disneyland is that if I turn around, my child might walk away or become lost. If my child wore a wristband, much like the ones used in hospitals, equipped with tracking capability, I’d know my child’s location at all times.”
That tracking capability would be derived from radio frequency identification – RFID – chips that transmit information to handheld readers. This technology is already being used to find lost pets and some theme parks are experimenting with RFID bracelets for patrons who want to know where their children are at all times.
In fact, Yang’s organic electronic devices, and the low-cost method of printing the circuits and other components that make up those devices, will have a wide-ranging impact on the growth of RFID technology and all the applications such technology make possible. For example, organic memory can be used in RFID technology to make inventory tracking of equipment or merchandise easier, faster and more likely error-free.
“Imagine you run a Wal-Mart store and you ask an employee to determine how many cans of tomato paste are left in stock,” posits Yang. “There will be errors as he counts every item, and even using a scanner it’s time-consuming, and the information will be outdated.”
But what if the cans of tomato paste themselves could report such information? “In ten minutes, the employee would know the inventory situation not only in the store but in the entire warehouse,” Yang said.
The same advantages could be realized in more dynamic environments, like aid shipments for humanitarian missions, or the movement of materiel for troops.
Another area being changed by organic electronics is full-color displays. Organic light-emitting devices (OLEDs) are beginning to replace liquid-crystal displays (LCDs) in laptops, in part because OLED displays emit brighter light and maintain viewing clarity from any angle. Other devices, such as cellular phones, game players and personal digital assistants, increasingly use OLED displays.
OLEDs can be printed onto flexible plastic foils rather than the more fragile, heavier glass surface upon which LCDs are deposited, and OLEDs offer better quality, crisper color and faster speed.
The materials and engineering advances emerging from Yang’s lab at UCLA, which currently has 21 students, are leading to the development of an entirely new class of organic semiconductor materials and RFID applications. As busy as the last year has been for Yang and his research team, even more exciting days may yet be ahead.
The research group’s web site is http://www.seas.ucla.edu/yylabs/. For more information about ORFID, please visit http://www.orfid.com/.
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