Home > Press > Stanford makes flexible carbon nanotube circuits more reliable and power efficient: Engineers invent a process to 'dope' carbon filaments with an additive to improve their electronic performance, paving the way for digital devices that bend
|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
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.
Stanford makes flexible carbon nanotube circuits more reliable and power efficient: Engineers invent a process to 'dope' carbon filaments with an additive to improve their electronic performance, paving the way for digital devices that bend
Stanford, CA | Posted on March 18th, 2014
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.
For more information, please click here
Copyright © Stanford School of Engineering
If you have a comment, please Contact
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
News and information
Graphene reduces wear of alumina ceramic March 26th, 2015
FEI Technology Award of the German Neuroscience Society Goes to Benjamin Judkewitz of the University of Berlin: Bi-annual award honors excellence in brain research during the German Neuroscience Society’s Annual Meeting, held 18-21 March 2015 March 26th, 2015
SUNY Poly & M+W Make Major Announcement: Major Expansion To Include M+W Owned Gehrlicher Solar America Corporation That Will Create up to 400 Jobs to Develop Solar Power Plants at SUNY Poly Sites Across New York State March 26th, 2015
Hong Kong Investors Bullish on Dais Analytic Invest $5.75M, Provide $60M Contract, and Create New Joint Venture Company March 26th, 2015
Haydale Announce Dedicated Graphene Inks Manufacturing Capability March 25th, 2015
Caltech scientists develop cool process to make better graphene March 18th, 2015
Breakthrough in OLED technology March 2nd, 2015
Improved fire detection with new ultra-sensitive, ultraviolet light sensor February 17th, 2015
SUNY POLY CNSE to Host First Ever Northeast Semi Supply Conference (NESCO) Conference Will Connect New and Emerging Innovators in the Northeastern US and Canada with Industry Leaders and Strategic Investors to Discuss Future Growth Opportunities in NYS March 25th, 2015
NXP and GLOBALFOUNDRIES Announce Production of 40nm Embedded Non-Volatile Memory Technology: Co-developed technology to leverage GLOBALFOUNDRIES 40nm process technology platform March 24th, 2015
Building shape inspires new material discovery March 24th, 2015
EEE Photonics Society’s Fourth Annual Optical Interconnects Conference Seeks to Bring Together the Latest Advanced Optical Interconnect Technologies, Systems & Architectures for the Next Generation of Supercomputers & Datacenters March 23rd, 2015
Carbon nanotube fibers make superior links to brain: Rice University invention provides two-way communication with neurons March 25th, 2015
Iranian Scientists Eliminate Expensive Materials from Diabetes Diagnosis Sensors March 25th, 2015
Effect of Carbon Nanotubes on Properties of Cement Composites Studied in Iran March 23rd, 2015
First proof of isolated attosecond pulse generation at the carbon K-edge March 20th, 2015
Industrial Nanotech, Inc. Announces Next Large Order from the Oil and Gas Industry March 26th, 2015
Quantum compute this -- WSU mathematicians build code to take on toughest of cyber attacks: Revamped knapsack code offers online security for the future March 26th, 2015
Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015
Square ice filling for a graphene sandwich March 26th, 2015