Featured Research

from universities, journals, and other organizations

Scientists Discover How To Make Nanostructures Assemble Themselves

Date:
November 19, 1999
Source:
Princeton University
Summary:
Princeton researchers have created ultrasmall plastic structures with a method that is cheaper and more versatile than previous techniques. The discovery has yielded surprising insights into the behavior of materials at very small scales, while spawning many basic research questions. It also could pave the way to a new generation of miniature products, from computer memory chips and video components to devices for sorting DNA molecules.

Technique could yield new generation of miniature electronics

PRINCETON, N.J. -- Princeton researchers have created ultrasmall plastic structures with a method that is cheaper and more versatile than previous techniques. The discovery has yielded surprising insights into the behavior of materials at very small scales, while spawning many basic research questions. It also could pave the way to a new generation of miniature products, from computer memory chips and video components to devices for sorting DNA molecules.

Professor of electrical engineering Stephen Chou and graduate student Larry Zhuang found that they could coax a flat sheet of plastic resin to assemble itself into a minute, perfectly ordered array of pillars -- with remarkably little specialized equipment. The pillars are a little more than half a micron (a millionth of a meter) in height and width. Viewing one of these pillars next to the head of a pin is like looking at a stack of about 15 quarters next to the dome of the U.S. Capitol. Chou expects that refinements of the technique will yield even smaller structures.

The researchers discovered the technique accidentally while working on another nano-fabrication process called imprinting. In that process, also invented by Chou, a pattern, or mask, is pressed into soft plastic polymer, like pressing minute fingers into wet plaster. The researchers were pressing a mask into polymer when dust prevented the two pieces from coming together. Afterwards, when they examined the polymer, they found that it contained a pattern of pillars even though the mask never touched it. Not only had the pillars grown by themselves, they had arranged themselves into a perfectly ordered array.

"It was a very surprising discovery," says Chou. "No one had ever seen such a thing."

Suddenly Chou had an entirely new production technique: simply bring the two pieces close together and let the pattern assemble itself. He dubbed the new approach LISA, for Lithographically Induced Self Assembly. Princeton University has filed for U.S. and international patents on the process, which Chou first described at the International Symposium on Cluster and Nanostructure Interfaces in October. He expects to publish the results in the December issue of the Journal of Vacuum Science and Technology.

The pillar pattern could be perfect for many applications, says Chou. The first use, he says, is likely to be in accelerating the development of organic light-emitting devices, which are the basis for the next generation of flat-panel displays and other video equipment. LISA would allow each dot of light, or pixel, to consist of a cluster of much smaller dots, instead of just being a single block of polymer material. That change would give the displays increased life spans and improved color reproduction, while making construction simpler and cheaper, says Chou.

A longer-term, but potentially further-reaching application is in the design of ultrasmall circuits. LISA could solve the increasingly difficult problem of attaching wires to ever-shrinking electronic devices. "Using the LISA process, you can fabricate your wires first, then it will assemble your devices between the wires on its own," says Chou. One example is the construction of DRAM memory chips for computers. "It's basically a paradigm shift in how you make memory."

Chou also believes LISA could be valuable to biophysicists at Princeton and elsewhere, who have found that passing DNA strands through a minute array of posts provides a cheap and simple way of sorting the molecules by size.

LISA is much better suited to mass production than the most common nano-fabrication technique, a slow and expensive process called photolithography, says Chou. So far LISA cannot make features as small as those produced by photolithography, but that may change. One hope is to set up a repeating process where a relatively large mask makes many pillars, which would then be used as masks to make a new set of even smaller pillars. "In principle, you can get smaller and smaller and smaller things," says Chou.

The LISA method complements Chou's earlier discovery of the imprinting technique. Imprinting has become a valuable tool because the arduous photolithography process only needs to be done once in making the mask - after that, nanostructures can just be stamped out. As a result, the cost is reduced more than 1,000-fold and opportunities arise for mass-produced products. LISA is even simpler: a carefully engineered mask is not necessary. The mask merely defines the outline of the pillar array.

"Here the polymer will form itself, without a mask. It's really wonderful," says Chou. Another advantage is that LISA could work with a wide variety of materials. Currently, Chou is testing LISA in the same material used in Plexiglas, but he believes the technique will work with metals and other non-polymer materials. Imprinting and photolithography work only in plastic polymers.

Despite many follow-up experiments, Chou is not entirely certain of the physics at work in making the pillars rise up toward the mask. In general, he believes it arises from inter-play between the electrostatic attraction of the mask and the hydrodynamic instability of the polymer. "There are just tons of new questions you need to ask," says Chou, "But it doesn't surprise us because we know we are working in a regime that no one has tried."

###

Please Note: Pictures are available at: www.princeton.edu/pr/pictures/other/LISA/


Story Source:

The above story is based on materials provided by Princeton University. Note: Materials may be edited for content and length.


Cite This Page:

Princeton University. "Scientists Discover How To Make Nanostructures Assemble Themselves." ScienceDaily. ScienceDaily, 19 November 1999. <www.sciencedaily.com/releases/1999/11/991119080041.htm>.
Princeton University. (1999, November 19). Scientists Discover How To Make Nanostructures Assemble Themselves. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/1999/11/991119080041.htm
Princeton University. "Scientists Discover How To Make Nanostructures Assemble Themselves." ScienceDaily. www.sciencedaily.com/releases/1999/11/991119080041.htm (accessed July 23, 2014).

Share This




More Matter & Energy News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
Powered by NewsLook.com
Boeing Ups Outlook on 52% Profit Jump

Boeing Ups Outlook on 52% Profit Jump

Reuters - Business Video Online (July 23, 2014) Commercial aircraft deliveries rose seven percent at Boeing, prompting the aerospace company to boost full-year profit guidance- though quarterly revenues missed analyst estimates. Bobbi Rebell reports. Video provided by Reuters
Powered by NewsLook.com
Europe's Car Market on the Rebound?

Europe's Car Market on the Rebound?

Reuters - Business Video Online (July 23, 2014) Daimler kicks off a round of second-quarter earnings results from Europe's top carmakers with a healthy set of numbers - prompting hopes that stronger sales in Europe will counter weakness in emerging markets. Hayley Platt reports. Video provided by Reuters
Powered by NewsLook.com
9/11 Commission Members Warn of Terror "fatigue" Among American Public

9/11 Commission Members Warn of Terror "fatigue" Among American Public

Reuters - US Online Video (July 22, 2014) Ten years after releasing its initial report, members of the 9/11 Commission warn of the "waning sense of urgency" in combating terrorists attacks. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins