Micro Swimming Robots A truly microscale (characteristic length of the robot doesn't exceed 100 um) swimming robot Goal: Developing a microscale swimming robot which operates in stagnation/low velocity flow field. Approach: Although advances in micro/nano-fabrication have led to realization of various miniature mobile robots; the most significant bottleneck for further miniaturization of mobile robots down to micrometer scale is the miniaturization of the on-board actuators and power sources required for mobility. Bioactuators are far superior to man-made actuators for micro/nanorobotics purposes. They are compact, efficient, and capable of producing complicated motions. However, isolating these actuators from living organisms and reconstituting them is an elaborate process with a very low yield. To circumvent this problem, in this project we use flagellar motors inside the intact cell of S. marcescens bacteria for controlled propulsion of a microscale swimming robot. Harvesting the motility of microorganisms, we have shown the feasibility of a novel technique for on/off controlled actuation at microscale. Current Status:Bacteria, only 0.5 um in diameter and 2 um long, are propelled by rotating their corkscrew like tails known as flagella at very high speed (~ 300 Hz). These flagella are only 20 nm in diameter and are about 10 um long. Here, S. marcescens bacteria are attached to Polystyrene (PS) microspheres via electrostatic, van der waals and hydrophobic interactions. As the attached bacteria rotate their flagella they push the microsphere forward. The on/off motion of the microspheres is controlled by introducing different chemicals into the experimental environment. To stop the motion, copper ions are introduced. These ions bond to the rotor of the flagellar motor and prevent its motion. To resume the motion we introduce another chemical called ethylenediaminetetraacetic acid (EDTA), which traps the copper ions attached to the rotor of the flagellar motor, allowing it to resume its motion. Benefits: We envision this robot having the capability to swim to inaccessible areas in human body and perform complicated user directed tasks such as diagnosis of diseases at early stages and targeted drug delivery. Videos: Video 1: 10 micron PS bead propelled by the attached S. marcescens bacteria. Video 2: Swimming Robot travelling through viscous fluid. Members: Metin Sitti Former Members: Eugene Cheung, Bahareh Behkam Publicity: New Scientist Papers: B. Behkam and M. Sitti, ''Bacterial Flagella-Based Propulsion and On/Off Motion Control of Microscale Objects,'' Applied Physics Letters, 90 (1):1-3. pdf. B. Behkam and M. Sitti, "Toward Hybrid Swimming Microrobots: Propulsion by an Array of Bacteria", Proceedings of IEEE 2006 International Conference of Engineering in Medicine and Biology,pp. 2421-2424, 2006.pdf B. Behkam and M. Sitti, "Design methodology for biomimetic propulsion of miniature swimming robots", Transactions of the ASME Journal of Dynamic Systems Measurement and Control,128 (1): 36-43 MAR 2006.pdf B. Behkam and M. Sitti, "Modeling and Testing of a Biomimetic Flagellar Propulsion Method for Microscale Biomedical Swimming Robots", Proceeding of 2005 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2005, pp. 37 - 42..pdf B. Behkam and M. Sitti, "E. Coli Inspired Propulsion for Swimming Microrobots", Proceedings of 2004 ASME International Mechanical Engineering Conference and Exposition, Anaheim, CA, 2004.pdf Funded by NSF (IIS-071335)

[swimming robot schematic] [Phase-contrast optical microscope images of a mobile 10 um PS bead with several S. marcescens attached to it at (a) t=0 and (b) t=6 s. PS bead's path is shown with rings.]