Tag Archives: M.P. Anantram

A bioelectronic future made possible with DNA-based electromechanical switch

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DNA-based electronics are discussed in the context of a Dec. 14, 2015 news item by Beth Ellison for Azonano about research into electromechanical switches at the University of California at Davis,

Researchers from the University of California, Davis (UC Davis) and the University of Washington have shown the possibility of using DNA-based electromechanical switches for nanoscale computing.

DNA is considered to be the molecule of life, and researchers have shown considerable interest in utilizing DNA as a nanoscale material in various applications.

A Dec. 14, 2015 UC Davis news release on EurekAlert, which originated the news item, provides more detail,

In their paper published in Nature Communications, the team demonstrated that changing the structure of the DNA double helix by modifying its environment allows the conductance (the ease with which an electric current passes) to be reversibly controlled. This ability to structurally modulate the charge transport properties may enable the design of unique nanodevices based on DNA. These devices would operate using a completely different paradigm than today’s conventional electronics.

“As electronics get smaller they are becoming more difficult and expensive to manufacture, but DNA-based devices could be designed from the bottom-up using directed self-assembly techniques such as ‘DNA origami’,” said Josh Hihath, assistant professor of electrical and computer engineering at UC Davis and senior author on the paper. DNA origami is the folding of DNA to create two- and three-dimensional shapes at the nanoscale level.

“Considerable progress has been made in understanding DNA’s mechanical, structural, and self-assembly properties and the use of these properties to design structures at the nanoscale. The electrical properties, however, have generally been difficult to control,” said Hihath.

New Twist on DNA? Possible Paradigms for Computing

In addition to potential advantages in fabrication at the nanoscale level, such DNA-based devices may also improve the energy efficiency of electronic circuits. The size of devices has been significantly reduced over the last 40 years, but as the size has decreased, the power density on-chip has increased. Scientists and engineers have been exploring novel solutions to improve the efficiency.

“There’s no reason that computation must be done with traditional transistors. Early computers were fully mechanical and later worked on relays and vacuum tubes,” said Hihath. “Moving to an electromechanical platform may eventually allow us to improve the energy efficiency of electronic devices at the nanoscale.”

This work demonstrates that DNA is capable of operating as an electromechanical switch and could lead to new paradigms for computing.

To develop DNA into a reversible switch, the scientists focused on switching between two stable conformations of DNA, known as the A-form and the B-form. In DNA, the B-form is the conventional DNA duplex that is commonly associated with these molecules. The A-form is a more compact version with different spacing and tilting between the base pairs. Exposure to ethanol forces the DNA into the A-form conformation resulting in an increased conductance. Similarly, by removing the ethanol, the DNA can switch back to the B-form and return to its original reduced conductance value.

One Step Toward Molecular Computing

In order to develop this finding into a technologically viable platform for electronics, the authors also noted that there is still a great deal of work to be done. Although this discovery provides a proof-of-principle demonstration of electromechanical switching in DNA, there are generally two major hurdles yet to be overcome in the field of molecular electronics. First, billions of active molecular devices must be integrated into the same circuit as is done currently in conventional electronics. Next, scientists must be able to gate specific devices individually in such a large system.

“Eventually, the environmental gating aspect of this work will have to be replaced with a mechanical or electrical signal in order to locally address a single device,” noted Hihath.

Here’s a link to and a citation for the paper,

Conformational gating of DNA conductance by Juan Manuel Artés, Yuanhui Li, Jianqing Qi, M. P. Anantram, & Joshua Hihath. Nature Communications 6, Article number: 8870 doi:10.1038/ncomms9870 Published 09 December 2015

This paper is open access.

Step closer to integrating electronics into the body

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The Sept. 20, 2011 news item (Proton-based transistor could let machines communicate with living things) on Nanowerk features a rather interesting development,

Human devices, from light bulbs to iPods, send information using electrons. Human bodies and all other living things, on the other hand, send signals and perform work using ions or protons.

Materials scientists at the University of Washington have built a novel transistor that uses protons, creating a key piece for devices that can communicate directly with living things.

Here’s a diagram from the University of Washington Sept. 20, 2011 article about the proton transistor by Hannah Hickey,

 

On the left is a colored photo of the UW device overlaid on a graphic of the other components. On the right is a magnified image of the chitosan fibers. The white scale bar is 200 nanometers. (Marco Rolandi, UW)

Here’s a little more about the proton transistor (from the Hickey article),

In the body, protons activate “on” and “off” switches and are key players in biological energy transfer. Ions open and close channels in the cell membrane to pump things in and out of the cell. Animals including humans use ions to flex their muscles and transmit brain signals. A machine that was compatible with a living system in this way could, in the short term, monitor such processes. Someday it could generate proton currents to control certain functions directly.

A first step toward this type of control is a transistor that can send pulses of proton current. The prototype device is a field-effect transistor, a basic type of transistor that includes a gate, a drain and a source terminal for the current. The UW prototype is the first such device to use protons. It measures about 5 microns wide, roughly a twentieth the width of a human hair.

As for the device (from the Hickey article),

The device uses a modified form of the compound chitosan originally extracted from squid pen, a structure that survives from when squids had shells. The material is compatible with living things, is easily manufactured, and can be recycled from crab shells and squid pen discarded by the food industry.

There is a minor Canadian connection,

Computer models of charge transport developed by co-authors M.P. Anantram, a UW professor of electrical engineering, and Anita Fadavi Roudsari at Canada’s University of Waterloo, were a good match for the experimental results.

If I understand this correctly, the computer models were confirmed by the experimental  results, which means the computer models can be used (to augment the use of expensive experiments) with a fair degree of confidence.

I am finding this integration of electronics into the body both fascinating and disturbing as per my paper, Whose electric brain? More about that when I have more time.