Inertial focusing microfluidics: single cell encapsulation, particle dynamics study, and rapid prototyping technique

Abstract

Inertial focusing microfluidics studies particle self-assembly in channel under certain fluidic conditions. It has been applied in cell/particle sorting, filtering, concentrating and separating. In this dissertation, a new application of inertial focusing microfluidics has been explored, particle focusing dynamics has been extensively studied under different fluidic conditions, and a novel microfluidic device rapid prototyping process has been presented. A straight channel microfluidic device designed and fabricated for cell encapsulation is presented. The device has the ability to continuously produce monodisperse microcapsules with controlled cell loading. Droplets of poly(ethylene-glycol)-diacrylate (PEGDA) containing 10.3-μm-diameter fluorescent polystyrene beads with a 60-70 μm diameter were generated and photopolymerized by UV. Production rate is higher than 200 capsules per second. Such straight channel device for cell encapsulation can be downsized by a curved inertial focusing channel. The curvature of the channel also introduces a secondary Dean vortex resulting in particle size-based sorting functionality, which is needed when cell samples have a finite size distribution. Particle dynamics is studied in a curved channel of different fluidic conditions. We investigated the continuous transition of particle behavior from the inertial force dominated regime (IFDR) to the Dean force dominated regime (DFDR). Close attention is paid to an intermediate range of Re (12.8--36.7), where novel observations were made along with numerical computations. Our research results potentially provide design and operation guidelines to achieve more accurate modeling of focusing and separation of particles. The current fabrication process of microfluidic devices is faced with several problems. The polymer material is incompatible with many common organic solvents and the fabrication process requires a physical mask and cleanroom facilities. To address these issues, a simple and cost-effective dynamic maskless on-chip microfabrication process is presented. The idea of multiple exposures utilizing Photoshop image processing technique enables scaling-up capacity (cm or larger) without compromising device resolution (sub-hundred μm). This process dramatically decreases design and fabrication time and cost. A solvent resistant material is used as the channel structural material. The bonding strength of devices thus made is 10 times higher than that of conventional polymer devices.