The goal of this project is to develop a microfluidic platform for studying the dynamic behavior of particle suspensions in microchannels with walls covered by biomimetic synthetic cilia. The microfluidic platform will be used to test a hypothesis that synthetic ciliated surfaces can be utilized to regulate transport of microscopic particles suspended in a flowing fluid. Computer simulations predict that synthetic cilia can create circulatory secondary flows that can either direct microscopic particles towards the ciliated wall or hydrodynamically repel them, and this cilium action is defined by their tilt with respect to the flow direction. Responsive compliant cilia will be manufactured from poly(dimethyl)siloxane (PDMS) with addition of magnetically-sensitive nanoparticles using soft lithography technique. In an alternative approach to make cilia responsive to magnetic field, cilia will be first sputtered with a very thin layer of Ti and then they will be coated with Ni using electroplating or e-beam evaporation. Experiments will be conducted in microchannels with regular arrays of responsive cilia that can be bent by either an imposed fluid flow or an external magnetic field. A combination of experiments in the microfluidic test cell with direct numerical simulations will be used to probe the interactions of the synthetic cilia with flowing fluids and examine how they affect deposition of micrometer-sized particles.
By creating synthetic, controllable cilia that can be incorporated into microfluidic devices, this project will establish a new approach for regulating motion of microparticles in microfluidic systems. Synthetic ciliated surfaces can be employed in a variety of applications that involve particle transport by fluid flow. In particular, ciliated surfaces could be used to selectively attract and trap particles from fluid. This will enable the development of novel filtration and sensory methods that could detect and isolate specific synthetic particles and biological cells. The ability of synthetic cilia to repel suspended particles could be harnessed in creating new self-cleaning and antifouling surfaces.
The goal of this EAGER grant is to develop a microfluidic platform for studying the dynamics of particles suspended in a fluid flowing along surfaces covered with hair-like elastic filaments, called cilia. To this end, we developed a technology to create synthetic surfaces covered with regular arrays of microscopic elastic posts characterized by high aspect ratio. These posts are made from a polymer material with embedded magnetic nanoparticles and, therefore, can be actuated by external magnetic field. We demonstrated the actuation and characterized post deformation in magnetic field. Such synthetic biomimetic surfaces decorated with elastic posts are needed to enable fundamental investigations of the dynamics of small particles transported by a flow of a viscous fluid near ciliated surfaces and to understand the impact of the surface structure on the particle motion. We have also developed a computational model that can simulate the motion of particles near surfaces with elastic magnetic cilia. We used this model to examine how magnetically actuated cilia can regulate particle deposition on surfaces. The results of our investigations will enable the design new structured surfaces that can actively regulate transport of particles towards and away for surfaces. For example, ciliated surfaces that can repel particles and reduce their deposition could be used to protect optical sensors and solar panels from dust maintaining their cleanness and efficient operation.
