Edwin W. H. Jager*, Olle Inganas, and Ingemar Lundstrom, "Microrobots for Micrometer-Size Objects in Aqueous Media: Potential Tools for Single-Cell Manipulation," Science, Vol. 288, No. 5475, pp. 2335 - 2338 (June 30, 2000).
Conducting polymers are excellent materials for actuators that are operated in aqueous media. Microactuators based on polypyrrole-gold bilayers enable large movement of structures attached to these actuators and are of particular interest for the manipulation of biological objects, such as single cells. A fabrication method for creating individually addressable and controllable polypyrrole-gold microactuators was developed. With these individually controlled microactuators, a micrometer-size manipulator, or microrobotic arm, was fabricated. This microrobotic arm can pick up, lift, move, and place micrometer-size objects within an area of about 250 micrometers by 100 micrometers, making the microrobot an excellent tool for single-cell manipulation.
Department of Physics and Measurement Technology, Division of Applied Physics, Linkopings universitet, S-581 83, Linkoping, SWEDEN.
* To whom correspondence should be addressed.. E-mail: firstname.lastname@example.org .
Could Prove Medical Boon
Randolph E. Schmid,
Associated Press Writer
2:55 PM EDT; June 29, 2000; Washington, D.C. (AP) -- Robots the size of the punctuation in this sentence could one day be used to move single cells or capture bacteria, their Swedish inventors say. The tiny robots are shorter than a hyphen and no wider than the period at the end of this sentence, according to Edwin W. H. Jager of Sweden's Linkoping University. The robots might be used as microsurgical instruments, explained Jager, "Maybe not (in the same) shape and form of these robots, but tools using the same micromuscle technology." Or, he added, these microrobots might be used to build other microdevices, just as cars are built by robots. In medicine, the robots could move a single cell from one point to another, he said. In experiments his team has used the robots to pick up and move tiny glass beads invisible to the unaided eye. Their work is reported in Friday's issue of the journal Science.
The microrobots are made of layers of polymer and gold and somewhat resemble a human arm. Currently, they remain in one spot, but Jager said he could foresee a time when they are made mobile. The robots have flexible elbow and wrist joints and the research team made them in various forms with hands made up of two to four fingers. Importantly, Jager noted, these devices can work while submerged in such liquids as blood, urine, and cell-culture medium, suggesting possible uses in biotechnology. Stuck on the end of a catheter, the microrobots might increase the range of surgeons.
Jager's co-authors, Olle Inganas and Ingemar Lundstrom, said in a statement that "one day, the robots might be usable to pick up tiny biological items and move them to an analysis station, and in groups to assemble microstructures." To make the microrobots move, the team used conducting polymers in the joints. These polymers will absorb charged particles called ions from the surrounding liquid, or shed them, depending on the electrical charge applied through tiny wires connected to the robot. Absorbing or shedding ions causes the polymers to swell or shrink, while the gold layer remains the same thickness. By properly arranging the polymers and gold layers the swelling or shrinking of the robot joints causes them to bend when various charges are applied, similar to changes in heat causing the movement of a thermostat. Bending of the polymer-gold layers causes the robot arm to flex at its elbow, bend the wrist, and close and open the fingers to grasp it. "Previous microrobots have included such things as electronic devices featuring rods and levers, artificial flying insects, and a walking silicon microrobot, but none could operate in water," Jager pointed out. His microrobots are 670 microns tall by [170 - 240] microns wide.