Microscale hybrid devices powered by biological flagellar motors

We are developing a series of micro hybrid devices based on tethered flagellar motors. Examples of the devices include a microfluidic pump and a micro ac dynamo. The microfluidic pump is realized through the tethering of a harmless strain of Escherichia coli (E. coli) cells to a microelectromechanical-systems-based microchannel. Each E. coli cell is about 3 /spl mu/m long and 1 /spl mu/m in diameter, with several flagella that are driven at the base by molecular rotary motors. The operational principle of the micro pump is based on the viscous pumping effect where continuous rotation of tethered cells in a microfluidic channel forms a fluidic conveyor belt that "drags" fluid from one end of the channel to the other. We used hydrodynamic loading to synchronize cell rotation in order to maximize the fluid pumping capability. The micro dynamo is realized through the integration of tethered flagellar motors with micro ferromagnetic beads and micro copper coils. The micro dynamo generates ac power by using the tethered cells to create a rotating magnetic field around the copper coils. Preliminary results indicate high-power density when compared to other biologically-based micro power generators. Note to Practitioners-The power supply remains a problematic area in the advancement of micro and nanoscale electromechanical systems. Flagellar motors, when tethered in microfluidic devices, provide a unique biological means to supply either mechanical or electrical power to these systems with high-power conversion efficiency. A major advantage of flagellar motor-powered systems is the absence of sophisticated control electronics since the motors are biologically self-sustained, so long as a supply of nutrients is provided to the tethered motors. Additionally, flagellar motors are relatively cost effective; they can be harvested fairly easily from cell growth using established biological protocols. However, integrating flagellar motors with artificial devices is extremely challenging. One of the major obstacles is maintaining the motility of the tethered motors in a microfabricated environment. To overcome this, research work has been focused on optimizing the chemo-mechanical behavior of the motors through genetic engineering and the development of an effective integration scheme for selective motor tethering at designated locations in a microfluidic device.