Think Small, Really Small

July 10, 2004
Developing Your Potential: Controlling the (Micro) Universe

Control systems drive actuators of various designs. Some control thousands of amps of electricity, some trigger minute current flows that cascade through computerized pathways, while others drive robots that build things. But the one attribute that most of these control systems share is that they work with tangible, "holdable," macroscopic things. But that is beginning to change.

The emerging science of nanotechnology works with things at the unbelievable scale of a few billionths of an inch (nanometers). For comparison, a typical bacterium is about 1,000 nanometers across, while the smallest virus particles measure 20 nanometers.

But that is old stuff compared to what Sandia National Labs is now doing—they've created a robot.

That doesn't sound particularly groundbreaking—until you realize that this robot, complete with feet and a prehensile tail for mobility, is a single molecule called a "motor protein!" Voila! One step towards being able to construct and control things at the atomic and molecular level.

Another, perhaps more interesting way of building things at the nanoscale is called SELF-assembly, where chemical reactions cause atoms and molecules to automatically come together in the desired configuration.

 "The emerging science of nanotechnology works with things at the unbelievable scale of a few billionths of an inch."

Researchers at NASA and USC have recently developed specialized molecular memory out of nanowires by causing them, 10 nanometers in diameter and 2,000 nanometers long, to spontaneously form.

Then, in a subsequent process of dipping the nanowires into a special solution, researchers caused each nanowire to self-assemble different layers upon itself to create molecular transistors along the wire. In fact, these molecules were rather special transistors.

Most typical transistors can define two states: Off or On (zero or one). But these nanowire transistors can assume one of eight states, allowing each transistor to hold three-bits of data rather than the traditional single bit. That trick further improves the storage capacity of this already ultra-dense memory to, potentially, 20 Gbit/cm2!

Another benefit of self-assembly is that, unlike the energy-intensive manufacturing techniques that we currently use to layer and carve-out transistors on chips, building things up from atoms generates little waste and takes but a fraction of the energy. For moreon this, check out recent publications from USC's Engineering Department and the American Society for the Advancment of Science's EurekAlert

In another direction, researchers are co-opting the techniques that nature has thoughtfully laid out for us to learn from. As described in an April 22, 2004 National Science Foundation press release, Duke University's Ashutosh Chilkoti and his team have used an ink made from enzymes to carve 400 nanometer wide troughs on a silicon chip without the heat, energy, and time required by traditional methods. You can find additional insights here.A different approach towards self-assembly is to use the stuff of life itself, DNA, to perform complex processes. According to Ehud Shapiro of Israel's Weizmann Institute of Science, reported in the April 24, 2004 edition of "... [DNA computers] harness the software-like ability of DNA strands to store information. Enzymes "read" chemical sequences on the DNA in a way that allows the computer to perform calculations." And these are but the tip of the nanotech iceberg. Federal funding is expected to reach $1 billion in 2005, while private funding may exceed that level of investment.

Nanotechnology is a technological race that, when won, promises to have far more of an impact on how we work, live, and play than the semiconductor and "computing" revolutions of the past 35 years. As these technologies mature; as the things we build shrink to nanometer sizes and create machines like the Sandia robot, and as self-assembled drugs become the norm within just a few years, the challenge on how to control (and keep control) of the processes and the environment will be substantial—and different from the challenges and solutions of today. Remember, the best relay-logic designer had little value to offer once the microcontroller took over, unless she looked in new directions. That's the control industry's challenge. That's your challenge!

Meanwhile, think small and don't blink!

Jeffrey R. Harrow

Principal, The Harrow Group

[email protected]

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