Microfluidics is a highly interdisciplinary research field which manipulates, controls and analyzes fluids in micro-scale for physical and bio/chemical applications. In this thesis, several aspects of fluid manipulations in micro-scale were studied, discussed and employed for demonstrations of practical utilizations.

To begin with, mixing in continuous flow microfluidic was raised and investigated. A simple method for mixing actuation based on magnetism was proposed and realized via integration of magnetically functionalized micropillar arrays inside the microfluidic channel. With such technique, microfluidic mixing could be swiftly switched on and off via simple application or retraction of the magnetic field. Thereafter, in Chapter 3 we mainly focused on how to establish sta...[ Read more ]

Microfluidics is a highly interdisciplinary research field which manipulates, controls and analyzes fluids in micro-scale for physical and bio/chemical applications. In this thesis, several aspects of fluid manipulations in micro-scale were studied, discussed and employed for demonstrations of practical utilizations.

To begin with, mixing in continuous flow microfluidic was raised and investigated. A simple method for mixing actuation based on magnetism was proposed and realized via integration of magnetically functionalized micropillar arrays inside the microfluidic channel. With such technique, microfluidic mixing could be swiftly switched on and off via simple application or retraction of the magnetic field. Thereafter, in Chapter 3 we mainly focused on how to establish stable while tunable concentration gradients inside microfluidic network using a simple design. The proposed scheme could also be modified with on-chip pneumatic actuated valve to realize pulsatile/temporal concentration gradients simultaneously in ten microfluidic branches. We further applied such methodology to obtain roughness gradients on Polydimethylsiloxane (PDMS) surface via combinations of the microfluidic network and photo-polymerizations. The obtained materials were utilized in parallel cell culture to figure out the relationship between substrate morphologies and the cell behaviors.

In the second part of this work, we emphasized on manipulations on microdroplets inside the microfluidic channel and explored related applications in bio/chemical aspects. Firstly, microdroplet-based microfluidic universal logic gates were successfully demonstrated via liquid-electronic hybrid divider. For application based on such novel scheme of controllable droplet generation, on-demand chemical reaction within paired microdroplets was presented using IF logic gate. Followed by this, another important operation of microdroplet - splitting - was investigated. Addition lateral continuous flow was applied at the bifurcation as a medium to controllably divide microdroplets with highly tunable splitting ratios. Related physical mechanism was proposed and such approach was adopted further for rapid synthesis of multi-scale microspheres.