Bacterial flagellar propulsion represents an extraordinary system in nature for generating motion at the micrometer scale due to their unique molecular polymeric structure adapting to different shapes, depending on the local chemical and flow conditions. Their motion induces a local flow that can be used to propel cells as well as much larger structures through a fluid environment. This collaborative research team plans to understand, to model and to exploit the physics of flagellar propulsion for use in engineered microfluidic systems. The objective of the program is to understand the fundamental scientific principles that govern the assembly and operation of flagella-propelled devices (both single swimmers and collectively-powered devices), as well as to demonstrate the enabling technologies necessary to harness polymeric protein nanostructures such as bacterial flagellar filaments on microstructures for use in micron-scale engineered propulsion systems. This collaborative proposal between Drexel University and Brown University is the first to focus on the specific characteristics associated with the polymorphic transformation of bacterial flagellar filaments to demonstrate the ability to move larger engineered elements through a microfluidic landscape in a controlled and directed manner. Fundamental scientific merits addressed by this proposal include using nanoscale flagellar filaments in engineered systems for micron-scale propulsion. Basic questions are to be answered regarding the mechanisms leading to self-coordination of flagellar filaments in responses to a variety of external stimuli. Possible coordination of flagellar filaments to transport microstructures in various microfluidic environments will be examined, thus enabling an entirely new class of swimming robotic systems with applications to bio-engineered actuators, drug delivery systems, and machines for micron-scale transport and assembly. Demonstration of the control of bacterial flagellar filaments at micro- and nanoscales and the ability to integration information technology with bio and nanotechnology will have great impact. The program will have an intensive outreach component, including active recruitment and training of women and underrepresented minorities engineers. The program will leverage and expand existing and proven programs already in place at Brown and Drexel. The PIs will additionally conduct outreach to inner-city high school student and teacher populations in both Providence and Philadelphia through the BROWNOUT (Brown) and INSPIRE (Drexel) programs.
The goal of the research project was to develop biologically inspired swimming microrobots utilizing the polymorphic transformation of bacterial flagellar filaments as s direct fluid actuation of a nanoscale structural "machine" at low Reynolds numbers. The bacterial flagella have been chosen as an ideal material for use in an artificial microswimming robot because of its excellent mechanical properties, their ability to self-assemble from monomers of flagellin protein into long filaments, the possibility for generic engineering of the structure and their suitability for chemical modification and functionalization. Through this program we have developed and achieved the necessary understanding and techinical infrastructure: 1. We have developed and fabricated novel biologically inspired swimming microbots that use bacterial flagellar filaments undergoing polymorphic transformation both in loaded and unlodaed conditions due to various external stimuli. 2. We have successfully demonstrated that synthetic microswimmers can be controlledy by a variety of appropriate stimuli, such as electric and magnetic fields. 3. We have conducted experiments, both at the macroscale and the microscale, of model systems illustrative of the microscale robotic systems, for the purposes of understanding the detailed fluid mechanics and coupled elastic structural behavior. 4. We have developed theoretical models, suitable for describing and predicting the behavior of flagellar systems subject to viscous forces. The funding results in the publication of 7 journal papers and one book chapter. A new lecture and laboratory module was developed and the 2 high school and 15 undergraduate students participated in research experiences.
