Featured Research

from universities, journals, and other organizations

MIT Team Develops New Way To Create Microscopic Patterns On Surfaces

Date:
December 2, 1998
Source:
Massachusetts Institute Of Technology
Summary:
The microscopic 3-D stripes of material that Assistant Professor Paula T. Hammond is depositing on thin gold wafers represent a new technique for creating patterns--and structures--on surfaces. The technique, which Professor Hammond pioneered some two years ago, involves "printing" a pattern onto a surface, then taking advantage of a material's electrical properties to build up layers of that material over the pattern.

Could become alternative to conventionalprocedures such as photolithography

CAMBRIDGE, Mass.--The microscopic 3-D stripes of material that AssistantProfessor Paula T. Hammond is depositing on thin gold wafers represent anew technique for creating patterns--and structures--on surfaces. Thetechnique, which Professor Hammond pioneered some two years ago, involves"printing" a pattern onto a surface, then taking advantage of a material'selectrical properties to build up layers of that material over the pattern.

Because the technique is relatively easy and inexpensive it couldbecome an alternative to conventional patterning procedures such as thephotolithography used in the manufacture of computer chips. One potentialapplication: printing electronic circuitry on treated paper or plasticsurfaces. "This would be much harder to do with photolithography and wouldalso be more expensive," Professor Hammond explained.

In the December 18 issue of the journal Advanced Materials,Professor Hammond and graduate student Sarah L. Clark, both of theDepartment of Chemical Engineering, report new advances in the work. Theseinclude the automation of the process and the ability to create morecomplex patterns using changes in processing conditions.

HOW IT WORKS

The technique specifically allows the researchers to create layersof polymer--materials made of repeating subunits--over a pattern (such as astripe). They can currently create stripes that are only about 3 1/2micrometers, or millionths of a meter, wide (a human hair is about 75micrometers in diameter). Layers of an inert material are deposited betweenthe stripes.

Professor Hammond's technique is a variation of one calledlayer-by-layer assembly, in which polymers with different charges aresequentially absorbed onto a surface. "For example, a polymer that'spositively charged will attract and absorb one that's negatively charged,"Professor Hammond said.

Layer-by-layer assembly, however, produces continuous polymerfilms. Professor Hammond is the first to create patterns. "Continuous films[like those produced via the original layer-by-layer technique] haveseveral applications, but those applications can be greatly increased ifyou can pattern the surface, tell the [polymer] film where to go,"Professor Hammond said.

Her variation begins by "stamping" a surface with the pattern ofinterest using microcontact printing, a technique developed at Harvard byProfessor Hammond's thesis advisor, Professor George Whitesides. ProfessorHammond took microcontact printing in another direction: she found that"ink" with specific properties would selectively attract certain polymers.Meanwhile the spaces between the stamped patterns, which she fills with theinert material, repel the polymer.

From there, just as with the original layer-by-layer deposition,Professor Hammond coaxes polymers of alternating charges to form layersover the pattern. Layers of inert material continue to fill in the gaps.

UNEXPECTED TWIST

In an unexpected twist, Professor Hammond's team has found thatchanging such things as the salt content or pH of the system can cause thepolymer and the inert material to switch allegiances. Stripes thatpreviously attracted the polymer now attract the inert material, and viceversa.

"This was a surprise," Professor Hammond said. Remembering themoment when her team first discovered the switch, initially with respect tosalt content, she continued: "We had to back up and say, 'wait a minutenow!' We had to check and double-check, until we could say, 'yes, this hashappened.'"

The researchers have since been instigating "reversals" to buildever more complicated structures. For example, as reported in AdvancedMaterials they can now produce "blankets" of polymer over the entiresurface, covering both the layers of polymer and the layers of inertmaterial. (In this case the reversal is incomplete, allowing polymer tospread over both types of material.) "It's really getting fun now,"Professor Hammond said.

The Advanced Materials paper also reports how the researchers havenow automated the process by adapting a machine originally designed forstaining slides used in biological studies. Among other advantages,automation means less time handling samples and better-controlledconditions. This has resulted in more uniform patterns, as well as anincrease in the number of layers that can be deposited. The researchershave also shown that the technique is reproducible (they have created up toten samples at a time).

Other members of Professor Hammond's research team are graduatestudents David M. DeWitt and Xueping Jiang, both of the Department ofChemical Engineering. Martha F. Montague, MIT SB 1998, was also on the team.

The work is funded by the Office of Naval Research and the MITCenter for Materials Science and Engineering.


Story Source:

The above story is based on materials provided by Massachusetts Institute Of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Massachusetts Institute Of Technology. "MIT Team Develops New Way To Create Microscopic Patterns On Surfaces." ScienceDaily. ScienceDaily, 2 December 1998. <www.sciencedaily.com/releases/1998/12/981202075758.htm>.
Massachusetts Institute Of Technology. (1998, December 2). MIT Team Develops New Way To Create Microscopic Patterns On Surfaces. ScienceDaily. Retrieved August 30, 2014 from www.sciencedaily.com/releases/1998/12/981202075758.htm
Massachusetts Institute Of Technology. "MIT Team Develops New Way To Create Microscopic Patterns On Surfaces." ScienceDaily. www.sciencedaily.com/releases/1998/12/981202075758.htm (accessed August 30, 2014).

Share This




More Matter & Energy News

Saturday, August 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Australian Airlines Relax Phone Ban Too

Australian Airlines Relax Phone Ban Too

Reuters - Business Video Online (Aug. 26, 2014) Qantas and Virgin say passengers can use their smartphones and tablets throughout flights after a regulator relaxed a ban on electronic devices during take-off and landing. As Hayley Platt reports the move comes as the two domestic rivals are expected to post annual net losses later this week. Video provided by Reuters
Powered by NewsLook.com
Hurricane Marie Brings Big Waves to California Coast

Hurricane Marie Brings Big Waves to California Coast

Reuters - US Online Video (Aug. 26, 2014) Huge waves generated by Hurricane Marie hit the Southern California coast. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Chinese Researchers Might Be Creating Supersonic Submarine

Chinese Researchers Might Be Creating Supersonic Submarine

Newsy (Aug. 26, 2014) Chinese researchers have expanded on Cold War-era tech and are closer to building a submarine that could reach the speed of sound. Video provided by Newsy
Powered by NewsLook.com
Breakingviews: India Coal Strained by Supreme Court Ruling

Breakingviews: India Coal Strained by Supreme Court Ruling

Reuters - Business Video Online (Aug. 26, 2014) An acute coal shortage is likely to be aggravated as India's supreme court declared government coal allocations illegal, says Breakingviews' Peter Thal Larsen. 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