Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A Misunderstanding Leads to Method for Making Nanowells

07.03.2011
A safe, simple, and cheap method of creating perfectly etched micron and smaller size wells in a variety of substrates has been developed by researchers in Penn State’s Department of Chemical Engineering. Similar patterned surfaces are currently made using complex and expensive photolithography methods and etch processes under clean room conditions and used in the fabrication of many optical, electrical, and mechanical devices.

The nanowell discovery was made in the labs of Darrell Velegol and Seong Kim by Velegol’s graduate student, Neetu Chaturvedi, and Kim’s graduate student, Erik Hsiao. An article detailing their research, “Maskless Fabrication of Nanowells Using Chemically Reactive Colloids,” appeared in the online edition of the journal Nano Letters in January 2011.

In collaboration with Chaturvedi, Hsiao was working on a project to adhere polystyrene on a silicon wafer to create nanostructures with known dimensions. When Hsiao asked her to heat one of his samples, a miscommunication led her to heat the polystyrene and silicon wafer at low temperature in water in the autoclave normally used for biological samples rather than in the vacuum furnace. When they looked at the samples under the atomic force microscope (AFM), they noticed holes had formed beneath the polystyrene particles.

Further examination under the scanning electron microscope (SEM) showed them perfectly etched, pyramidal shaped holes in the substrate below the places where the amidine-functionalized polystyrene latex colloid particles had adhered to the silicon dioxide on the surface of the silicon wafer.

“We saw three holes in the sample at the first AFM imaging and didn’t know what it meant since we expected pancake-like polymer patches on the sample,” said Hsiao. They took the sample to their advisers, who were both surprised by the etched wafer. By going over the steps the students had taken, the researchers realized that the wells were produced when the water hydrolized the amidine group in the particle, and through a series of chemical reactions, created a hydroxide ion that etched the well into the silicon wafer. The holes were uniform and their size and depth were totally dependent on the size of the original polystyrene particle, although the orientation of the silicon crystal affected the shape of the wells. In one orientation (100), the wells were perfect four-sided inverted pyramids. In the other orientation (111), the wells were perfect hexagons. The four researchers called them nanowells, because the bottom dimension of the wells was only a couple of nanometers across. They soon realized that they had discovered a new maskless method for creating structures in silicon without the elaborate steps normally required in the clean room.

“We’re delivering hydroxide ions directly to where we want to etch,” Velegol explained. “It’s much safer and cheaper than electron beam and X-ray lithography. It’s so safe that you could practically eat these particles without any harm.”

“We think this is a quite general discovery,” Kim added. “It’s a way to deliver chemistry locally rather than in bulk. Many metals, ceramics, and other materials can be etched with this technique.”

Another potential benefit of the discovery is the ability to create patterns on curved surfaces, something that is difficult to do with conventional photolithography. Since the particles are suspended in water, they can adhere to the surface of any shape and space themselves evenly over the surface. The researchers are just beginning to come up with intriguing ideas for how to use the simple technique.

Many breakthroughs come from accidents, Velegol remarked, because once something is known, people work on it very rapidly until they have filled in all the pieces and there is less to discover. Accidents are out of the pattern. “It’s one of those situations like Pasteur said where chance favors the prepared mind. We would never even have thought to try this kind of chemistry. But Neetu had been working with these colloids for several years, and Erik had experience with the AFM, so they were well prepared to take advantage of the accident,” Velegol concluded.

Neetu Chaturvedi, Ph.D., recently defended her thesis and is now a researcher with DuPont. Erik Hsiao is a graduate student in chemical engineering. Darrell Velegol is professor of chemical engineering and Seong Kim is associate professor of chemical engineering. Both are faculty in the Materials Research Institute where the AFM and SEM work was performed. Contact them by email at velegol@psu.edu and shkim@engr.psu.edu. This work was supported by the National Science Foundation (Grant Nos. IDR-1014673 and CMMI-1000021).

The Materials Research Institute facilitates and coordinates Penn State’s interdisciplinary research activity in materials science and engineering. The Millennium Science Complex, the university’s largest facility for scientific research, is scheduled to open in July 2011. It will bring together the Materials Research Institute and the Huck Institutes of the Life Sciences in the integration of the physical and life sciences with engineering.

| Newswise Science News
Further information:
http://www.psu.edu

Further reports about: Nanowells SEM chemical engineering chemical reaction silicon wafer

More articles from Materials Sciences:

nachricht A materials scientist’s dream come true
21.08.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

nachricht Novel sensors could enable smarter textiles
17.08.2018 | University of Delaware

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>