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Big Promise in Thinking Small

Researchers are building tiny robots in hopes of opening exciting new frontiers in medicine, computing and many other fields.


The idea: Armies of robotic insects.

The possibilities: Farmers "infest" crops with thousands of sensor ants to report soil and weather conditions in the farthest reaches of the fields. For the espionage-oriented, deploy electronic dust motes to cross enemy lines on the wind, unnoticed. Or, more mundanely, plant one on little Jimmy's sneaker and know where he is at all times.

The world of MEMS, or microelectromechanical systems, is progressing toward self-sufficient micro-robots. On an even smaller scale, NEMS, the nanoscale equivalent, are popping onto the scene and gaining national attention.

Researchers are convinced that these small devices, particularly nanostructures, will open new frontiers in medicine, sensor technology and computing and even change how we control matter.

Last month, the National Science Foundation announced a Nanoscale Science and Engineering initiative to provide an estimated $74 million in funding for nanotechnology research. President Clinton has requested up to $495 million for nanotechnology research in his fiscal 2001 budget. He acknowledged in a speech at Caltech in January that, "Some of our research goals may take 20 or more years to achieve, but that is precisely why there is an important role for the federal government."

In June, graduate student Edwin Jager and his colleagues at Sweden's Linkopings Universitet unveiled the first micro-robot--actually an arm--to operate underwater, an important feature for biological uses.

In fact, by design, the tiny limb must operate in salty water containing electrolytes, similar to body fluids. By making ions--electrically charged particles--flow through its miniature "muscles" and "joints," the scientists cause shrinking or swelling that correspond to contracting or extending a tiny arm, wrist and hand.

Jager constructed the arm--no bigger than this dash--using photolithography, a.k.a. microchip-building technology.

Talented hands and chemistry created a flat version of the arm by applying layers of gold and a conducting polymer on a silicon wafer in specific patterns and then etching out desired shapes. Then a "glue" layer was dissolved to release the 3-D functioning arm. Using this process, 140 arms were made on one quarter of the 10-centimeter wafer: Each arm consisted of an elbow joint still attached to the wafer, a wrist joint and two to four finger joints, each independently controlled.

Each arm can lift and move a "boulder-sized" glass bead--relatively speaking, of course. It can sort beads onto conveyor tracks. Although there is not a huge market for sorting of teeny-tiny beads, the movements could be applied to human cells one day, Jager said.

"It's always been science fiction, you know, robots in the body . . . and now it's real. This is one step, one demonstration of the possibilities of microsystems technology," Jager said.

Scaling down to the parts of a cell, for repairing individual cells or DNA, requires thinking even smaller, down to the nanometer. The concept of "nano" has crept into everyday slang as in, "give me a nanosecond," but to scientists "nano" means working on the scale of one billionth of a meter. For reference, a nanoparticle used in the lab compared with a paper clip stood on end is like a ladybug compared with 20 stacked Eiffel Towers.

"I worked at the micron scale [before], and the jump to nanoscale is a whole new way of working. It's a frontier," said Sheffer Meltzer of USC's Laboratory for Molecular Robotics.

Not visible through even the highest powered optical microscope, nanoparticles can be seen only with a scanning probe microscope, which detects the tiniest deflection as a probe moves over a nanoparticle obstruction. It translates the deflections into an artificial visual image so that researchers can "see" their work.

They can also use the microscope to manipulate nanoparticles--a prerequisite for any future nanomachines.

Aristides Requicha, head of the multidisciplinary USC lab, and his colleagues have made considerable strides in nanofabrication. After discovering how to move nanoparticles in two dimensions, the next goal was to add the third dimension.

To tackle 3-D construction, the lab developed a method using "nanocement." Researchers position particles on the first "floor," then grow layers of oxidized silicon around them, anchoring them in place. Then, the next layer of particles is added and linked to the first layer with chemical "glue." When construction is completed, the cement layers are dissolved to leave a free-standing 3-D nanostructure.

The USC lab is also working toward single-molecule chemical sensors and single-electron transistors and has a National Science Foundation grant to pursue a "DNA editing" project. The lab has achieved particle pushing underwater--necessary for constructing nanorobots to work inside the body.

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