CPS-Medium: Dense Networks of Bacteria Propelled Micro-Robotic Swarms
New computational framework and physical platform for designing stochastic micro-robotic swarms

Goal: To develop and control dense networks of bacteria-driven swimming micro-robots

Approach: When scaling down robots to the micro-scale, developing a reliable and efficient source of actuation becomes a critical issue. To address this issue, we employ a bio-hybrid approach. We make use of the highly efficient flagellar motors of bacteria. When the bacteria are attached to micro-objects, they act as on-board actuators, providing a propulsive force and torque which results in net motion of the object. We aim to manipulate the overall motion of the micro-robots by controlling the attachment and motility of the bacteria. This single micro-robot approach can be extended to a swarm of bio-hybrid micro-robots, which can be controlled by utilizing the cooperative behavior of the bacteria.

Benefits: Flagellated bacteria provide a promising and powerful source for advanced micro-actuation for micro-mechanism systems. We envision that swarms of these bio-actuated devices will be used in minimally invasive medical diagnosis and targeted drug delivery applications. Furthermore, these bacteria-driven micro-robots could also be applied in searching and remote sensing applications.

Current Status: Serratia marcescens bacteria (0.5 um in diameter and 2 um long) are propelled by rotating their corkscrew-like tails known as flagella at very high speeds (~ 100 Hz). Each flagellum is 20 nm in diameter and about 10 um long. The bacteria are attached to polystyrene (PS) microbeads via electrostatic, van der waals, and hydrophobic interactions. The propulsive force and torque provided by the bacteria result in a translational and rotational motion of the bead. We have developed a defocused optical tracking method, enabling us to track the bead motion in 3-D. We are also developing methods to improve the steering control of the beads. We have demonstrated that the speed and directionality of the motion can be improved by patterning the microbeads, which isolates the bacterial attachment to specific sites on the bead. We are also exploring the use of chemical gradients to improve the directionality of the motion. This method utilizes the chemotactic response of bacteria, which directs bacteria toward or away from a chemical source.

Videos: (newest to oldest)

• Video 1: Chemotactic Steering Response of Bacteria Propelled Micro-spheres (2012) [YouTube video]
• Video 2: 30 micron size PS bead rotation due to bacterial propulsion (2011) [YouTube video]
• Video 3: 10 micron PS bead propelled by the attached S. marcescens bacteria [link]
• Video 4: Swimming robot travelling through viscous fluid [link]

Media Appearances: New Scientist

Members: Eric Diller, Rika Wright Carlsen, Jiang Zhuang, Matthew Edwards, Cecile Pacoret, Paul Bogdan, Guopeng Wei, Lina Gonzalez, Philip LeDuc, Radu Marculescu, Metin Sitti

Past Members: Albert Liu, Dongwook Kim, Jack Singleton, Eugene Cheung, Bahareh Behkam

Papers:

• M. Edwards, R. Carlsen, and M. Sitti, "Near and Far-Wall Effects on the Three Dimensional Motion of Bacteria-Driven Microbeads," Applied Physics Letters (Under Review).
• D. Kim, A. Liu, E. Diller, and M. Sitti, "Chemotactic Steering of Bacteria Propelled Microbeads," Biomed Microdevices 14, 1009-17, Dec 2012. [link]
• W. Ruder and P. LeDuc, "Cells Gain Traction in 3D", PNAS 109, 11060-11061, July 2012. [link]
• W. Ruder, C. Hsu, B. Edelman Jr., R. Schwartz, and P. LeDuc, "Biological colloid engineering: Self-assembly of dipolar ferromagnetic chains in a functionalized biogenic ferrofluid", Applied Physics Letters 101, 063701, 2012. [link]
• P. Bogdan, G. Wei, and R. Marculescu, "Modeling Populations of Micro-robots for Biological Applications", 2nd IEEE International Workshop on Molecular and Nanoscale Communications, Ottawa, Canada, June 2012. [link]
• D. Kim, A. Liu, and M. Sitti, "Chemotactic Behavior and Dynamics of Bacteria Propelled Microbeads", Int. Conf. on Intelligent Robots and Systems, San Francisco, 2011. [link]
• J. Singleton, E. Diller, T. Andersen, S. Regnier, and M. Sitti, "Micro-Scale Propulsion using Multiple Flexible Artificial Flagella" (invited paper), Int. Conf. on Intelligent Robots and Systems, San Fransisco, 2011. [link]
• V. Arabagi, B. Behkam, E. Cheung, and M. Sitti, "Modeling of Stochastic Motion of Bacteria Propelled Spherical Microbeads," Journal of Applied Physics 109, 114702, 2011. [link]
• B. Behkam and M. Sitti, "Bacterial Flagella-Based Propulsion and On/Off Motion Control of Microscale Objects," Applied Physics Letters, vol. 90, pp. 23902-23904, 14 Jan. 2007. Also appeared on the Virtual Journal of Nanoscale Science & Technology, vol. 15, no. 2, January 15, 2007. [link]
• B. Behkam and M. Sitti, "Towards Hybrid Swimming Microrobots: Bacteria Assisted Propulsion of Polystyrene Beads", Proceedings of IEEE 2006 International Conference of Engineering in Medicine and Biology,pp. 2421-2424, 2006. [link]
• 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. [link]
• 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. [link]
• 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.

Funded by NSF CPS-Medium Project (CNS-1135850)