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Volume 2, Issue 4
May/June 2002

Outline List

In This Issue
Marrying Microsystems and Nanoscience

Let There Be (Sun)Light

If You Can See This, You're Too Close

A BiD for Better Design

Berkeley Engineering History: The Release of SPICE




Lab Notes, Research from the College of Engineering

The science-fiction fantasy of nanotechnology — building novel structures, devices, and materials at the atomic or molecular scale — is becoming a reality. For the great potential of nanoscience and nanotechnology to be fully realized, however, research efforts must cross many disciplines, from electrical engineering, mechanical engineering, materials science, and computer science to bioengineering, chemistry, and physics.

Nowhere is this cross-disciplinary approach fostered more than at UC Berkeley. Each month, Lab Notes is proud to present the work of nanotechnology researchers from the College of Engineering and our collaborators across the campus.

Marrying Microsystems and Nanoscience
by David Pescovitz

illustration of cantilever reactions

In this illustration, the cantilever on the left bends as PSAs (prostate cancer markers) bind to it. The other cantilevers remain straight because the molecules they're exposed to are not PSAs. The laser measures the deflection of each cantilever.
Image courtesy Kenneth Hsu/UC Berkeley & the Protein Data Bank

The Book of Life is now open in front of us in the form of our genetic code. But for the Human Genome Project to live up to its potential in the fight against disease, we must understand the proteins encoded by the genome, an endeavor known as proteomics.

"As mechanical engineers, we're tackling proteomics through the mechanics of molecules," says Mechanical Engineering professor Arun Majumdar.

And so far, this unique approach has paid off. The researchers' biochemo-optomechanical (BioCOM) chip uses an array of diving board-like cantilevers that bend in the presence of proteins characteristic of prostate cancer, the No. 2 killer of men in this country. Thanks to its innovative engineering, the BioCOM detects the prostate-specific antigens (PSAs) at levels 20 times less than necessary to catch the cancer in its earliest stages. Eventually, the cantilever approach could lead to a drug discovery chip with the ability to analyze thousands of compounds, highlighting those that may be useful weapons against a specific disease.

"In this post-genomic era, the high-throughput analysis of proteins and nucleic acids is of primary importance," Majumdar says. "This could lead to fast screening and molecular profiling for many diseases and a possible cancer chip for detecting cancer."

The BioCOM is one of several UC Berkeley projects at the intersection of nanotechnology and MEMS, micro-electromechanical systems being mass manufactured in a process similar to the way microchips are made.

"We are bridging the length scale between the nanoscale and the microscale," says Majumdar, who collaborated on the project with graduate students and researchers from Berkeley, USC and Oak Ridge National Laboratory.

The BioCOM's silicon nitride cantilevers, each half the width of a human hair, are coated with certain antibodies that only bind to specific proteins, for example, PSAs. As the proteins bind to the cantilevers, they push and pull to make room for each other. This change in conformation causes the cantilever to bend. A laser measures this deflection, which may only be a few nanometers depending on the amount of protein in the sample.

Prof. Majumdar with microscope

This scanning thermal electron microscope, the most advanced of its kind, will enable Arun Majumdar to create three-dimensional thermal maps of transistors and other miniature devices. (Click for larger image.)
Peg Skorpinski photo

"You have to be quantitative," Majumdar says. "It is the balance of the protein in your cell, its expression, that determines if the cell is cancerous or diseased in some other way."

Traditional "one analyte at a time" assays require molecules to be flagged with fluorescent tags for identification, a problem in drug discovery as the similarity in size between the drug molecule and the tag may inhibit binding. Majumdar's mechanical approach negates the need for tags while enabling samples to be processed en masse.

"If you have an array of thousands of pixels, you can functionalize each pixel with molecules from drug libraries to see what candidate drugs bind to which target," Majumdar says.

Your Turn

Will the BioCOM chip and nanotechnology innovations like it change our lives? How soon?

We want to hear from you...

The BioCOM is only one of several innovative projects in Majumdar's Nanoengineering Laboratory. His group is also studying the thermal conductivity of nanowire arrays grown by researchers in Berkeley's College of Chemistry. Understanding heat transport in nanowire arrays could lead to tiny solid-state refrigerators to cool high-performance microprocessors or thermoelectric devices that convert waste heat into power. And in another bio-nano effort, Majumdar is looking at how complementary strands of DNA might be used as transports and glue for assembling inorganic nanoparticles into desired patterns. Once the nanoparticles are properly connected, the DNA is burned off.

"We are not only looking at how mechanical engineering can help biology, but at how biology can help us," Majumdar says. "The biological toolbox is already there; we just have to learn how to use it."

Arun Majumdar's home page

UC Berkeley Nano-Engineering Laboratory

Lab Notes is published online by the Public Affairs Office of the UC Berkeley College of Engineering. The Lab Notes mission is to illuminate groundbreaking research underway today at the College of Engineering that will dramatically change our lives tomorrow.

Editor, Director of Public Affairs: Teresa Moore
Writer, Researcher: David Pescovitz
Designer: Robyn Altman

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© 2002 UC Regents. Updated 5/1/02.