Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stanford makes flexible carbon nanotube circuits more reliable and power efficient

18.03.2014

Engineers invent a process to 'dope' carbon filaments with an additive to improve their electronic performance, paving the way for digital devices that bend.

Engineers would love to create flexible electronic devices, such as e-readers that could be folded to fit into a pocket. One approach they are trying involves designing circuits based on electronic fibers, known as carbon nanotubes (CNTs), instead of rigid silicon chips.

Flexible CNT Chip

Stanford engineers have developed an improved process for making flexible circuits that use carbon nanotube transistors, a development that paves the way for a new generation of bendable electronic devices.

Credit: Bao Lab, Stanford University

But reliability is essential. Most silicon chips are based on a type of circuit design that allows them to function flawlessly even when the device experiences power fluctuations. However, it is much more challenging to do so with CNT circuits.

Now a team at Stanford has developed a process to create flexible chips that can tolerate power fluctuations in much the same way as silicon circuitry.

"This is the first time anyone has designed a flexible CNT circuits that have both high immunity to electrical noise and low power consumption, " said Zhenan Bao, a professor of chemical engineering at Stanford with a courtesy appointment in Chemistry and Materials Science and Engineering.

The group reported its findings in the Proceedings of the National Academy of Sciences. Huiliang (Evan) Wang, a graduate student in Bao's lab, and Peng Wei, a previous postdoc in Bao's lab, were the lead authors of the paper. Bao's team also included Yi Cui, an associate professor of materials science at Stanford, and Hye Ryoung Lee, a graduate student in his lab.

In principle, CNTs should be ideal for making flexible electronic circuitry. These ultra thin carbon filaments have the physical strength to take the wear and tear of bending, and the electrical conductivity to perform any electronic task.

But until this recent work from the Stanford team, flexible CNTs circuits didn't have the reliability and power-efficiency of rigid silicon chips.

Here's the reason. Over time, engineers have discovered that electricity can travel through semiconductors in two different ways. It can jump from positive hole to positive hole, or it can push through a bunch of negative electronic like a beaded necklace. The first type of semiconductor is called a P-type, the second is called and N-type.

Most importantly, engineers discovered that circuits based on a combination of P-type and N-type transistors perform reliably even when power fluctuations occur, and they also consume much less power. This type of circuit with both P-type and N-type transistors is called complementary circuit. Over the last 50 years engineers have become adept at creating this ideal blend of conductive pathways by changing the atomic structure of silicon through the addition of minute amounts of useful substances – a process called "doping" that is conceptually akin to what our ancestors did thousands of years ago when they stirred tin into molten copper to create bronze.

The challenge facing the Stanford team was that CNTs are predominately P-type semiconductors and there was no easy way to dope these carbon filaments to add N-type characteristics.

The PNAS paper explains how the Stanford engineers overcame this challenge. They treated CNTs with a chemical dopant they developed known as DMBI, and they used an inkjet printer to deposit this substance in precise locations on the circuit.

This marked the first time any flexible CNT circuit has been doped to create a P-N blend that can operate reliably despite power fluctuations and with low power consumption.

The Stanford process also has some potential application to rigid CNTs. Although other engineers have previously doped rigid CNTs to create this immunity to electrical noise, the precise and finely tuned Stanford process out performs these prior efforts, suggesting that it could be useful for both flexible and rigid CNT circuitry.

Bao has focused her research on flexible CNTs, which compete with other experimental materials, such as specially formulated plastics, to become the foundation for bendable electronics, just as silicon has been the basis for rigid electronics.

As a relatively new material, CNTs are playing catch up to plastics, which are closer to mass market use for such things as bendable display screens. The Stanford doping process moves flexible CNTs closer toward commercialization because it shows how to create the P-N blend, and the resultant improvements in reliability and power consumption, already present in plastic circuits.

Although much work lies ahead to make CNTs commercial, Bao believes these carbon filaments are the future of flexible electronics, because they are strong enough to bend and stretch, while also being capable of delivering faster performance than plastic circuitry.

"CNTs offer the best long term electronic and physical attributes," Bao said.

Tom Abate | EurekAlert!
Further information:
http://www.stanford.edu

Further reports about: CNT CNTs Engineering N-type circuitry filaments fluctuations materials transistors

More articles from Power and Electrical Engineering:

nachricht Nano-scale process may speed arrival of cheaper hi-tech products
09.11.2018 | University of Edinburgh

nachricht Nuclear fusion: wrestling with burning questions on the control of 'burning plasmas'
25.10.2018 | Lehigh University

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>