Hydrodynamic Trapping and Encapsulation of Microparticles

Single cell measurements are hard to obtain and current technology does not allow for control of external inputs on the cell at the same time the measurements are taking place. Microfluidic technology such as hydrodynamic trapping presents a robust method capable of actively observing the cell while stressing it with inputs. Such devices are easily fabricated and span a wide range of applications related to single cell studies and bead based assays. In the following paper, a novel technique for trapping and encapsulation of single microparticles using hydrodynamic traps is proposed and its feasibility is tested in CFD simulations and PDMS devices. Simulation studies were performed to optimize the parameters such as channel width, length and height to achieve maximum trapping and cell viability. Microfluidic devices with hydrodynamic traps were fabricated in order to trap microparticles and cells. Oil was flowed after the particles were trapped in order to isolate the traps and form aqueous droplets. The single particle trapping efficiency was found to be ~99% in many of the devices tested while the oil isolation suffered due to the aqueous medium leaking out through the other side of the traps. Reversing the oil flow was not tried as complete isolation of the traps was not achieved. Although, results indicate that decreasing the Q1/Q2 ratio below 1 would result in better isolation of the traps by the oil.