Towards the manufacturing of microfluidic devices : fluid flow in multilayer devices as a test case

Abstract

In this work, the area of microfluidics is analyzed for advances that could be made in the manufacturing of a microfluidic device, and then one area - the alignment of multilayer devices - is selected for greater focus. Microfluidics is an emerging technology receiving much attention to date for its potential in biological, chemical, and medical applications. It could bring costs savings and contamination-reducing disposable parts, but only if certain hurdles relating to the design and fabrication of the devices are overcome. In order to better understand the manufacturing issues, a survey of the applications is presented, with a focus on the functional requirements for the fabrication of the devices. Then, a survey of the techniques currently in use to create microfluidic devices is presented, again focusing on the issues related to their fabrication and scalability to large-volume manufacturing. In order to address the issues that arise during the surveys, two new directions are submitted. First, a "test device" is proposed. This test device will consist of a variety of sample features characteristic of many different types of microfluidic devices, in a range of carefully selected dimensions.

(cont.) The test device serves as a tool for evaluating different processes for relative capabilities in creating the microfluidic structures. Second, multilayer devices, an area of concern that will arise as the field moves forward, is explored further. Specifically, the impact on fluid flow parameters of alignment of the two layers, a process currently performed manually, is investigated. A theoretical model of the scenario, which acts as a pressure barrier to laminar flow in a rectangular channel, is established, identifying the parameter of interest, the coefficient of pressure loss across the multilayer joint between layers. Then a series of sample multilayer parts with target dimensions of 100 gm x 100 pm x 3 mm is constructed. The pressure loss coefficients were obtained as a function of the cross-sectional area of the joint, from as small as 0.71 for very large joints up to over 1000 for joints that are only 30 gm of the channel in width. Failure pressure for the devices was found to be on the order of 140 kPa.