DESIGN, SIMULATION AND FABRICATION OF MICROFLUIDIC CHANNELS

Abstract

This dissertation work involves the fabrication of deep microfluidic channels on low-cost glass substrate. These channels are enclosed within glass to substrate-glass bonding, forming closed microfluidic channel. Bi-layer molybdenum is used as mask for the wet etching of the microfluidic channels. This mask could sustain the diluted BOE attack with magnetic bead stirring for the duration of 8 hours which is longer than reported till date. The maximum etch depth obtained is 390 μm. The work also reports the influence of etch rate on channel dimensions in wet etching. It has been reported that the etching depth increases with increase in channel width attributed to micro-loading. It has been observed that compared to BOE mixed HCl, BOE combined with HNO3 has higher etch rate and smoother channels. Glass to glass bonding has been done by a unique and custom made clamp without the use of heavy weights. The fabricated glass microfluidic channel can find applications in the microfluidic heat sink in electronic circuits and in bio-fluidic sensing which utilizes optical methods. The deep channel can also find application to integrate other structures like cantilever or valves. The work also involves easy fabrication of microfluidic chip without the need of clean room by using 3D printed mould for PDMS. The design of micro channel fabricated is a combination of Y channel, and asymmetric circular split and recombine mixers for the mixing of reagents in the laminar flow regime. The channels fabricated are 300 μm in width and 80 μm in height. This in plane, passive mixing device is easy to fabricate and low cost. Experimental analysis was carried out by mixing yellow and blue color fluid which resulted in green color fluid at the output indicating successful mixing of two colored fluids. The simulation of microfluidic channel is done for different depth and width, and it has been verified that higher depth and lower width assist in good mixing. The effect of diffusion constant has been seen by simulation and it has been concluded that the channel designed in the present work is advantageous for mixing low concentration fluid and large size molecules. The dependence of mixing on Reynolds number has been simulated in the designed channel. The designed channel has been simulated for particle trapping and velocity profile. Effect of curvature and variation of design has been done for a micromixer. Finally, mathematical equations are used to find Reynolds number, time of mixing and mixing efficiency for fabricated channel. The work done is an adequate preliminary optimization, which can aid in fabrication of devices for further advanced applications which can be pathbreaking in the field of medical devices and Lab on a chip applications.