Part of the  

Solid State Technology

  Network

About  |  Contact

Headlines

Headlines

Research Alert: March 18, 2014

Creating a graphene-metal sandwich to improve electronics

Researchers have discovered that creating a graphene-copper-graphene “sandwich” strongly enhances the heat conducting properties of copper, a discovery that could further help in the downscaling of electronics.

The work was led by Alexander A. Balandin, a professor of electrical engineering at the Bourns College of Engineering at the University of California, Riverside and Konstantin S. Novoselov, a professor of physics at the University of Manchester in the United Kingdom. Balandin and Novoselov are corresponding authors for the paper just published in the journal Nano Letters. In 2010, Novoselov shared the Nobel Prize in Physics with Andre Geim for their discovery of graphene.

In the experiments, the researchers found that adding a layer of graphene, a one-atom thick material with highly desirable electrical, thermal and mechanical properties, on each side of a copper film increased heat conducting properties up to 24 percent.

“This enhancement of copper’s ability to conduct heat could become important in the development of hybrid copper — graphene interconnects for electronic chips that continue to get smaller and smaller,” said Balandin, who in 2013 was awarded the MRS Medal from the Materials Research Society for discovery of unusual heat conduction properties of graphene.

Whether the heat conducting properties of copper would improve by layering it with graphene is an important question because copper is the material used for semiconductor interconnects in modern computer chips. Copper replaced aluminum because of its better electrical conductivity.

Surface characteristics influence cellular growth on semiconductor material

Changing the texture and surface characteristics of a semiconductor material at the nanoscale can influence the way that neural cells grow on the material.

The finding stems from a study performed by researchers at North Carolina State University, the University of North Carolina at Chapel Hill and Purdue University, and may have utility for developing future neural implants.

“We wanted to know how a material’s texture and structure can influence cell adhesion and differentiation,” says Lauren Bain, lead author of a paper describing the work and a Ph.D. student in the joint biomedical engineering program at NC State and UNC-Chapel Hill. “Basically, we wanted to know if changing the physical characteristics on the surface of a semiconductor could make it easier for an implant to be integrated into neural tissue – or soft tissue generally.”

The researchers worked with gallium nitride (GaN), because it is one of the most promising semiconductor materials for use in biomedical applications. They also worked with PC12 cells, which are model cells used to mimic the behavior of neurons in lab experiments.

In the study, the researchers grew PC12 cells on GaN squares with four different surface characteristics: some squares were smooth; some had parallel grooves (resembling an irregular corduroy pattern); some were randomly textured (resembling a nanoscale mountain range); and some were covered with nanowires (resembling a nanoscale bed of nails).

Very few PC12 cells adhered to the smooth surface. And those that did adhere grew normally, forming long, narrow extensions. More PC12 cells adhered to the squares with parallel grooves, and these cells also grew normally.

About the same number of PC12 cells adhered to the randomly textured squares as adhered to the parallel grooves. However, these cells did not grow normally. Instead of forming narrow extensions, the cells flattened and spread across the GaN surface in all directions.

More PC12 cells adhered to the nanowire squares than to any of the other surfaces, but only 50 percent of the cells grew normally. The other 50 percent spread in all directions, like the cells on the randomly textured surfaces.

“This tells us that the actual shape of the surface characteristics influences the behavior of the cells,” Bain says. “It’s a non-chemical way of influencing the interaction between the material and the body. That’s something we can explore as we continue working to develop new biomedical technologies.”

First methodology to analyze nanometer line pattern images

In the study, the researchers grew PC12 cells on GaN squares with four different surface characteristics: some squares were smooth; some had parallel grooves (resembling an irregular corduroy pattern); some were randomly textured (resembling a nanoscale mountain range); and some were covered with nanowires (resembling a nanoscale bed of nails).

Very few PC12 cells adhered to the smooth surface. And those that did adhere grew normally, forming long, narrow extensions. More PC12 cells adhered to the squares with parallel grooves, and these cells also grew normally.

About the same number of PC12 cells adhered to the randomly textured squares as adhered to the parallel grooves. However, these cells did not grow normally. Instead of forming narrow extensions, the cells flattened and spread across the GaN surface in all directions.

More PC12 cells adhered to the nanowire squares than to any of the other surfaces, but only 50 percent of the cells grew normally. The other 50 percent spread in all directions, like the cells on the randomly textured surfaces.

“This tells us that the actual shape of the surface characteristics influences the behavior of the cells,” Bain says. “It’s a non-chemical way of influencing the interaction between the material and the body. That’s something we can explore as we continue working to develop new biomedical technologies.”

Tags: , , ,

Leave a Reply