Navigation Links
Tiny channels carry big information
Date:12/14/2010

They say it's the little things that count, and that certainly holds true for the channels in transmembrane proteins, which are small enough to allow ions or molecules of a certain size to pass through, while keeping out larger objects. Artificial fluidic nanochannels that mimic the capabilities of transmembrane proteins are highly prized for a number of advanced technologies. However, it has been difficult to make individual artificial channels of this size until now.

Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have been able to fabricate nanochannels that are only two nanometers (2-nm) in size, using standard semiconductor manufacturing processes. Already they've used these nanochannels to discover that fluid mechanics for passages this small are significantly different not only from bulk-sized channels, but even from channels that are merely 10 nanometers in size.

"We were able to study ion transport in our 2-nm nanochannels by measuring the time and concentration dependence of the ionic conductance," says Arun Majumdar, Director of DOE's Advanced Research Projects Agency Energy (ARPA-E), who led this research while still a scientist at Berkeley Lab. "We observed a much higher rate of proton and ionic mobility in our confined hydrated channels up to a fourfold increase over that in larger nanochannels (10-to-100 nm). This enhanced proton transport could explain the high throughput of protons in transmembrane channels."

Majumdar is the co-author with Chuanhua Duan, a member of Majumdar's research group at the University of California (UC) Berkeley, of a paper on this work, which was published in the journal Nature Nanotechnlogy. The paper is titled "Anomalous ion transport in 2-nm hydrophilic nanochannels."

In their paper, Majumdar and Duan describe a technique in which high-precision ion etching is combined with anodic bonding to fabricate channels of a specific size and geometry on a silicon-on-glass die. To prevent the channel from collapsing under the strong electrostatic forces of the anodic bonding process, a thick (500 nm) oxide layer was deposited onto the glass substrate.

"This deposition step and the following bonding step guaranteed successful channel sealing without collapsing," says Duan. "We also had to choose the right temperature, voltage and time period to ensure perfect bonding. I compare the process to cooking a steak, you need to choose the right seasoning as well as the right time and temperature. The deposition of the oxide layer was the right seasoning for us."

The nanometer-sized channels in transmembrane proteins are critical to controlling the flow of ions and molecules across the external and internal walls of a biological cell, which, in turn, are critical to many of the biological processes that sustain the cell. Like their biological counterparts, fluidic nanochannels could play critical roles in the future of fuel cells and batteries.

"Enhanced ion transport improves the power density and practical energy density of fuel cells and batteries," Duan says. "Although the theoretical energy density in fuel cells and batteries is determined by the active electrochemical materials, the practical energy density is always much lower because of internal energy loss and the usage of inactive components. Enhanced ion transport could reduce internal resistance in fuel cells and batteries, which would reduce the internal energy loss and increase the practical energy density."

The findings by Duan and Majumdar indicate that ion transport could be significantly enhanced in 2-nm hydrophilic nanostructures because of their geometrical confinements and high surface-charge densities. As an example, Duan cites the separator, the component placed between the between the cathode and the anode in batteries and fuel cells to prevent physical contact of the electrodes while enabling free ionic transport.

"Current separators are mostly microporous layers consisting of either a polymeric membrane or non-woven fabric mat," Duan says. "An inorganic membrane embedded with an array of 2-nm hydrophilic nanochannels could be used to replace current separators and improve practical power and energy density."

The 2-nm nanochannels also hold promise for biological applications because they have the potential to be used to directly control and manipulate physiological solutions. Current nanofluidic devices utilize channels that are 10-to-100 nm in size to separate and manipulate biomolecules. Because of problems with electrostatic interactions, these larger channels can function with artificial solutions but not with natural physiological solutions.

"For physiological solutions with typical ionic concentrations of approximately 100 millimolars, the Debye screening length is 1 nm," says Duan. "Since electrical double layers from two-channel surfaces overlap in our 2-nm nanochannels, all current biological applications found in larger nanochannels can be transferred to 2-nm nanochannels for real physiological media."

The next step for the researchers will be to study the transport of ions and molecules in hydrophilic nanotubes that are even smaller than 2-nm. Ion transport is expected to be even further enhanced by the smaller geometry and stronger hydration force.

"I am developing an inorganic membrane with embedded sub-2 nm hydrophilic nanotube array that will be used to study ion transport in both aqueous and organic electrolytes,' Duan says. "It will also be developed as a new type of separator for lithium-ion batteries."


'/>"/>

Contact: Lynn Yarris
lcyarris@lbl.gov
510-486-5375
DOE/Lawrence Berkeley National Laboratory
Source:Eurekalert  

Related biology news :

1. CSHL researchers identify gene that helps plant cells keep communication channels open
2. Journal of General Physiology explores mysteries of TRP channels in latest Perspectives series
3. New research helps explain how connexin hemichannels are kept closed
4. International collaboration by scientists culminates in novel ion channels database
5. Researcher says microchannels could advance tissue engineering methods
6. Nervy research: Researchers take initial look at ion channels in a model system
7. MDC researchers develop new tool to investigate ion channels
8. A lab-on-a-chip with moveable channels
9. Chloride channels render nerve cells more excitable
10. Earthworm activity can alter forests carbon-carrying capabilities
11. Polarized light guides cholera-carrying midges that contaminate water supplies
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Tiny channels carry big information
(Date:6/7/2016)... June 7, 2016  Syngrafii Inc. and San ... relationship that includes integrating Syngrafii,s patented LongPen™ eSignature ... This collaboration will result in greater convenience for ... union, while maintaining existing document workflow and compliance ... ...
(Date:6/2/2016)...   The Weather Company , an IBM Business (NYSE: ... capability in which consumers will be able to interact with ... via voice or text and receive relevant information about the ... Marketers have long sought an advertising solution that can create ... relevant and valuable; and can scale across millions of interactions ...
(Date:5/24/2016)... patient care by providing unparalleled technology to leaders of the medical imaging industry.  As ... added to the range of products distributed by Ampronix. Photo - ... ... ... ...
Breaking Biology News(10 mins):
(Date:12/5/2016)... 2016  Eisai Inc. announced today final results ... rufinamide, which were presented at the 2016 Annual ... from December 2-6 in Houston, Texas ... and cognitive data showed that patients who received ... tolerability profiles, cognitive development and behavior, compared to ...
(Date:12/4/2016)... Dec. 3, 2016  In five studies being presented ... Annual Meeting and Exposition in San Diego ... to improve the delivery of life-saving treatments to patients ... are designed to carry therapies directly to the sites ... could provide a substantial advantage over traditional, systemic methods. ...
(Date:12/2/2016)... 2016 Amgen (NASDAQ: AMGN ) and ... submission of a Marketing Authorization Application (MAA) to the European ... Avastin ® (bevacizumab). The companies believe this submission is ... "The submission of ABP 215 to the EMA ... oncology portfolio," said Sean E. Harper , M.D., executive ...
(Date:12/2/2016)... ... December 01, 2016 , ... Aerocom Healthcare ... American hospitals, will present its chain-of-custody solution for tracking and securing medications at ... Nev., Dec. 4-8, 2016. , Aerocom has a proven solution for tracking medications ...
Breaking Biology Technology: