Nano-engineered living bacterial motors for active microfluidic mixing.
Active micromixers with rotating elements are attractive microfluidic actuators in many applications because of their mixing ability at a short distance. However, miniaturising the impeller design poses technical challenges including the fabrication and driving means. As a possible solution inspired by macro magnetic bar-stirrers, this study proposes the use of tethered, rotating bacteria as mixing elements. A tethered cell is a genetically engineered, harmless Escherichia coli (E. coli) attached to a surface by a single, shortened flagellum. The tethered flagellum acts as a pivot around which the entire cell body smoothly rotates. Videomicroscopy, image analysis and computational fluid dynamics (CFD) are utilised to demonstrate a proof-of-concept for the micro mixing process. Flow visualisation experiments show that a approximately 3 microm long tethered E. coli rotating at approximately 240 rpm can circulate a 1 microm polystyrene bead in the adjacent area at an average speed of nearly 4 microm/s. The Peclet (Peb) number for the stirred bead is evaluated to approximately 4. CFD simulations show that the rotary motion of a tethered E. coli rotating at 240 rpm can generate fluid velocities, up to 37 microm/s bordering the cell envelop. Based on these simulations, the Strouhal number (St) is calculated to about 2. This hybrid bio-inorganic micromxer could be used as a local, disposable mixer.
Al-Fandi
M
M
Jordan University of Science and Technology, Mechanical Engineering Department, Irbid, Jordan. mohamed_alfandi@just.edu.jo
Jaradat
M A K
MA
Fandi
K
K
Beech
J P
JP
Tegenfeldt
J O
JO
Yih
T C
TC
D004926:Escherichia coli / Q000166:cytology / Q000502:physiology*; D005407:Flagella / Q000502:physiology* / Q000648:ultrastructure; D005818:Genetic Engineering / Q000379:methods; D044085:Microfluidics / Q000379:methods*; D009038:Motion; D009068:Movement / Q000502:physiology; D036103:Nanotechnology / Q000379:methods*