Laser-Assisted Fast Prototyping of Microdevices for the Microfluidic Manipulation of Liquid and Cells

Microfabrication is an everlasting topic in the evolution of the microfluidic communities. Being fast, automated, material-versatile, and clean-room-free, laser-assisted fabrication and prototyping has drawn increasing attention in the manufacturing of microdevices and become more and more appealing to innovators interested in the commercialization of lab-on-a-chip products. In this dissertation, the power of laser assisted fabrication is exploited in the fast prototyping of various types of microdevices that enables sophisticated manipulation of liquid or cells.

An introduction of the principles, procedures and recent applications of laser assisted fabrication is presented in Chapter 1. In Chapter 2 a novel, scanner-based profiling method is described for the examination of laser ablated microstructures in PDMS and polymers. In Chapter 3, a one-way check valve is created through laser-assisted fabrication and serves as the key component of passive flow control in a finger-driven microdevice that enables precise metering and delivery of multiple reagents. In Chapter 4 the acoustic differential extraction (ADE) is reported, in which sperm cells are separated from mock sexual assault samples by ultrasonic standing waves generated in a laser-ablated glass-PDMS-glass microdevice. Laser-ablated check valves are integrated onto the microdevice to control the on-chip flow switching in the multiple steps of sperm extraction including sample infusion, washing and elution. The power of laser is further extended to glass in Chapter 5, in which the surface of glass, after being cleaned by laser beams, shows remarkable hydrophilicity that enables the direct retaining and partitioning of aqueous liquid into droplet arrays by simple action of dipping-and-pulling. Suspension of cells can be easily arrayed by this process for high-throughput bioassays. Finally, concluding remarks and future directions are outlined in Chapter 6.