Low-Cost Microfluidic Channel Fabrication for Lab-on-a-Chip Application Using Optimized SU-8 Soft Lithography

Microtechnology and microfluidic systems are areas whose growth has soared exponentially over the past few years. Offering reduced reagent consumption, high throughput, and unprecedented automation, the “lab on a chip” systems are often seen as preferable, especially because of their size, which makes them suitable for mobile field laboratories. Their highly reduced consumption of samples and reagents, system cost, size, power, and remarkably fast analysis time has proved it preferable while working on rapid on-site issues. MEMS (Microelectromechanical systems) and LOC (Lab on a chip) evolution using soft lithography have proved very useful, but often require the use of expensive, industrial equipment, a change of which is seen in this experiment.The study and optimization of epoxy-based negative photoresist (SU-8) microstructures through a low-cost process and without the need for cleanroom facility will be presented in this work. It will be demonstrated that the Ultraviolet Rays (UV) exposure equipment, commonly used in the UV glue curing industry, can replace the more expensive and less available equipment. Moreover, high transparency masks, printed in a photomask, will be used, instead of expensive chromium masks. The fabrication of well-defined SU-8 microchannels with high aspect ratios are hoped to be successfully demonstrated with those facilities. In addition, fluid flow through the micro-channels fabricated using SU-8 soft lithography will be tested and characterized using Micro-PIV (Particle Image Velocimetry) system. To show microchannel functionality, Micro PIV was used to test channel operation, proving no irregularities or blockers inside the channel. Micro PIV is a tool used to measure the velocity profile across a plane in a microfluidic device. It utilizes a volume illumination technique where the light source and the view field are introduced through the same optics. The fluid velocity in this microchannel was measured by the displacement of small tracer particles added to the channel’s fluid, which was pumped into the microchannel using a syringe pump. In this study the fabrication of a microchannel under cheaper, more affordable equipment was applied to optimize production of microfluidic structures. Micro PIV was used to determine optimal functionality of the microchannel and secure its smooth operation. It was found that the fabricated microchannel works smoothly without any leaking under different flow rate. Although in the microscopic view of the channel some irregularities were found in the side wall of the channel due to the UV light difractios. In the future, this information will be used to successfully fabricate new medical and fast acting technology like point of care testing diagnostic system.