Biologically inspired robotic microswimmers

摘要

Most of the conventional drugs have narrow therapeutic window and require localization to a specific site in the body. However, the current drug delivery systems lack in terms of target specificity and result in uptake of drugs by other cells or tissues which can lead to toxic manifestations. Biomimetics hold great promise to facilitate the cellular uptake of the drugs and as well as for drug targeting applications. The main goal of this project is to develop and test a biomimetic, micro-scale drug delivery system with active propulsion. The device is based on the propulsion systems of the naturally occurring bacteria such as Escherichia Coli or Salmonella typhimurium and utilizes flagellar filaments of genetically modified S. typhimurium. The device is comprised of the polystyrene (PS) bead coupled with many flagella conjugated magnetic beads. The PS bead replaces a drug delivery system such as drug filled vesicle or polymeric encapsulations. Besides the role of coupler for PS bead, the flagella act as fluidic actuators for device propulsion. An externally generated 3-D magnetic field using a set of electromagnetic coils in an approximately Helm Holtz configuration is utilized to induce rotation in the flagella conjugated magnetic bead. The rotating flagella create propulsion and the directed motion of the microswimmer is achieved through polymorphic transformations of the flagella filaments, as found in natural, polarly flagellated bacteria. The homogenous rotating magnetic field is generated by alternating current (AC) power supplies connected to coils, which will be controlled by LABVIEW. A high speed camera and a specific rotating magnetic field (created by adjusting the supplied voltage and frequency) will help provide real-time control of the microswimmer. The analysis of flagella hydrodynamics is performed to obtain the theoretical microswimmer velocity as a function of the rotational frequency and the number of flagella required for a single microswimmer. E--lectro-magnetic physics and COMSOL Multi-physics are used to model the magnetic control system and provide uniform magnetic field at the middle point of the coils. Understanding the flagella hydrodynamics and limitations, this project deliverable will be an accurately functionalized, controllable microswimmer prototype for biomimetic drug delivery.