Tuesday, October 02, 2007

Bacteria Breakthrough For Microdot Printed Circuits

You can see above a not-to-scale graphic showing "how catalyst (blue hollow-ended beads) dangles from patterned stamp, while dye particles (gold balls) are bonded to DNA chains to make DNA coating visible. After stamp (blue) presses into DNA coating (yellow) at center the catalyst detaches dye and DNA chain's tip (bottom right). That disruption creates patterning in DNA coating (top right)." Credits: graphic by Alexander Shestopalov, caption by Duke University - Here is a link to a larger version of this graphic.

Bacteria Breakthrough For Microdot Printed Circuits

An E. Coli infection to the human body is not a good thing. The infection may create symptoms that include severe abdominal cramping, bloody diarrhea, and sometimes nausea with vomiting.

Bacteria, however, has enzyme properties that allow one to improve the preciseness of the surface pattern of a printed circuit one-hundred fold of traditional inking methods.

This discovery will have a tremendous effect on the depth of computer processes that can be placed on a single chip, in that, this inkless technique could be used to build complex nanoscale devices with unprecedented precision to create microdevices such as labs-on-a-chip.

This excerpted from Wikipedia –

1) After the discovery of microtechnology (~1958) for realizing integrated semiconductor structures for microelectronic chips, these lithography-based technologies were soon applied in pressure sensor manufacturing (1966) as well.

Due to further development of these usually CMOS-compatibility limited processes, a tool box became available to create micrometre or sub-micrometre sized mechanical structures in silicon wafers as well: the Micro Electro Mechanical Systems (MEMS) era (also indicated with Micro System Technology - MST) had started.

2) Lab-on-a-chip (LOC) is a term for devices that integrate (multiple) laboratory functions on a single chip of only millimeters to a few square centimeters in size and that are capable of handling extremely small fluid volumes down to less than pico liters. Lab-on-a-chip devices are a subset of MEMS devices and often indicated by "Micro Total Analysis Systems" (┬ÁTAS) as well.

Microfluidics is a broader term that describes also mechanical flow control devices like pumps and valves or sensors like flowmeters and viscometers. However, strictly regarded "Lab-on-a-Chip" indicates generally the scaling of single or multiple lab processes down to chip-format, whereas "┬ÁTAS" is dedicated to the integration of the total sequence of lab processes to perform chemical analysis.

Reference Here>>

Over time, this can have an effect on the general miniaturization of electronic devices. Hand held devices just may become finger held devices.

This excerpted EurekAlert! from Duke University –

Using catalysts to stamp nanopatterns without ink
Contact: Monte Basgall, Duke University - Public release date: 26-Sep-2007

Using enzymes from E. coli bacteria, Duke University chemists and engineers have introduced a hundred-fold improvement in the precision of features imprinted to create microdevices such as labs-on-a-chip.

Their inkless microcontact printing technique can imprint details measuring close to 1 nanometer, or billionths of a meter, the Duke team reported in the Sept. 24, 2007 issue of the Journal of Organic Chemistry.

"This has a lot of potential, because we don't have the resolution issue," said Robert Clark, a professor of mechanical engineering and materials science and dean at Duke’s Pratt School of Engineering. “The really important part is that with a biological catalyst there’s no ink involved,” added Duke chemistry professor Eric Toone.

Clark, Toone and three graduate students authored the report on their study, which was funded by the National Science Foundation (NSF).

In traditional microcontact printing -- also called soft lithography or microstamping -- an elastic stamp’s end is cast from a mold created via photolithograpy – a technique used to generate microscopic patterns with light. Those patterns are then transferred to a surface by employing various biomolecules as inks, rather like a rubber stamp.
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A shortcoming of traditional microcontact printing is that pattern transfer relies on the diffusion of ink from the stamp to the surface. This same diffusion spreads out beyond the limits of the pattern as the stamp touches the surface, degrading resolution and blurring the feature edges, Clark and Toone said.

Because of this mini-blurring, the practical limit to defect-free patterning is “in excess of 100 nanometers,” said the report, whose first author, Phillip Snyder, is a former Toone graduate student now working as a postdoctoral researcher in Whitesides’ group.

A 100 nanometer limit of resolution is about 1,000 times tinier than a human hair’s width. While that seems very precise, the Duke team now reports it can boost accuracy limits to less than 2 nanometers by entirely eliminating inking.

Clark and graduate student Matthew Johannes crafted a microstamp out of a gel-like material called polyacrylamide, which compresses more uniformly than the silicone material known as PDMS which is normally used in microstamping.

In lieu of ink, Snyder, Toone and graduate student Briana Vogen suspended a biological catalyst on the stamp with a molecular “tether” of amino acids. For this proof-of-principle demonstration, Toone’s team chose as a catalyst the biological enzyme exonuclease I, derived from the bacterium E. coli.

In one set of experiments, the polyacrylamide stamp pattern bearing the tethered enzymes was then pressed on a surface of gold that had been covered with a uniform coating of single-stranded DNA molecules. The DNA molecules had also been linked to fluorescent dye molecules to make the coating visible under a microscope.

Wherever the enzyme met the DNA, the end of the DNA chain and its attached dye were broken off and removed. That created a dye-less pattern of dots on the DNA coating, each dot measuring about 10 millionths of a meter diameter each.

The microdots are very precise because the catalyst that created them could not shift its position more than the length of its chemical tether -- less than 1 nanometer, the Duke team reported. "Whether the stamp was left on for a short period of time, or for days, the pattern did not change,” Clark said.

The inkless microstamp could also re-use the same suspended catalyst molecule repeatedly. “Enzymes can deteriorate with extended use,” Clark acknowledged. “But because of our tether attachment chemistry, we can easily wash the old enzyme off, put on a new one and keep going,” Clark said.

In follow-up research, Clark and Toone are now evaluating more durable microstamping materials attached to longer lasting catalysts that are non-enzymatic.
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“Soft lithography has really revolutionized the field of surface science over the last 30 years,” said Toone. “And I honestly believe that using catalysts instead of diffusive processes is going to become the way that soft lithography is done in the future.”
This discovery illustrates that it's a very small world, after all!

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