With no guide wires or tethers, scientists at Duke University have been able to maneuver microrobots using electrical field, leading them in an intricate dance that could eventually allow them to work cooperatively to perform assorted tasks. Self assembly is a hot new field that will only grow with time and as interest in nanoresearch heats up. The little microrobots will likely someday allow for such self assembly, but for now they're content to dance the night away.
The tiny robots pirouette in video captured by researchers over a 1 mm dance floor -- the robotic dance was set to the Strauss waltz. The new robots are 100 times smaller than any previous robots of their kind, measuring just microns. And they weigh less than a hundredth of the previous smallest bots.
Bruce Donald, a Duke Professor of computer science and biochemistry, who led the project states, "It's marvelous to be able to do assembly and control at this fine a resolution with such very, very tiny things."
The new machines are sometimes known as microelectromechanical system (MEMS) microrobots. They are small enough that they can navigate over chip surfaces, allowing them to assist in tiny on-chip labs, such as chemical sensors. The little devices turn and pivot by using a boom like arm, which is drawn down to the surface by electric charges. Researchers compare the mechanism to a dirt biker using their heel to navigate around a turn.
As well as taking new records in size and weight, the new bots also are the first microrobots to perform a group maneuver under the same control position. By using slight variations in the bots' different dimensions and stiffness and mathematical modeling, researchers can use a single varying electrical field to allow the robots to execute organized sets of commands.
The team’s research is presented in a report to the Hilton Head Workshop on Solid State Sensors, Actuators and Microsystems in South Carolina. In the report presented on June 1 and 2, Donald's team summarizes the breakthrough stating, "Our work constitutes the first implementation of an untethered, multi-microrobotic system."
How the tiny robots are built and controlled will be explained in more detail in a paper in the upcoming edition of the Journal of Microelectromechanical Systems.
Professor Donald brings a great deal of experience to the table. He has been working on miniature MEMs robots since 1992. The research led him to Cornell and then at Stanford and Dartmouth and finally to Duke. Professor Donald had initial success with creating micro-robots which simulated cillia, rocking back and forth to move tiny computer chips or other objects. He describes, "[The robots] move objects such as microchips on top of them in the same way that a singer in a rock band will crowd surf. We made 15,000 silicon cilia in a square inch."
The next step was a 2006 February report in the Journal of Microelectromechanical Systems, in which Donald and colleague Christopher Levey, Dartmouth College physicist, and Donald’s graduate student Igor Paprotny detailed the current design. The new robot, finally built and fully working measures a mere 60 microns (µm) wide, 250 microns (µm) long and 10 microns (µm) high. They scavenged their power from a charged surface. The microrobots are propelled by their “scratch-drive” motion actuator -- the arm that swings the main body around its end point. The result is the microrobot movies in tiny steps of 10 to 20 nm, but can move very fast, taking up to 20,000 steps a second.
The concept of one signal controlling many responses is analogous to the way cells use proteins to respond specifically to chemical signals, says Donald. Professor Donald has worked extensively in computational biochemistry and biology. The culmination of his and his teams work is the ability of allowing multiple separate robots to be hided into a "team huddle". These huddles could lead to something greater; says Donald, "Initially, we wanted to build something like a car that could drive around at the microscopic scale. Now what we’ve been able to do is create the first microscopic traffic jam."
However the microrobots' progress has taken time; the bots in larger form first were designed by Donald between 1997 and 2002, but it took three more years to move under global control and additional three years to move more than one independently at once. Donald explains the challenges, stating, "The hard thing was designing how multiple microrobots can all work independently, even while they receive the same power and control."
The research has finally advanced to the point where it may have practical applications in fields such as medicine. The Duke Institute for Brain Sciences is sponsoring research to see if the new robots can be used to insert carbon nanotube electrodes into brain cells. The bots could also be possibly used in drug delivery.
The robotics project itself is funded by a grant from the National Institutes of Health and the Department of Homeland Security.