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 Linear potentiometer LRW2/3 - Maximum precision with many measuring points
17.05.2017 | WayCon Positionsmesstechnik GmbH

nachricht First flat lens for immersion microscope provides alternative to centuries-old technique
17.05.2017 | Harvard John A. Paulson School of Engineering and Applied Sciences

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: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>