Fabrication of Microfluidic Devices Containing Patterned Microwell Arrays

Abstract

A rapid fabrication and prototyping technique to incorporate microwell arrays with sub-10 μm features within a single layer of microfluidic circuitry is presented. Typically, the construction of devices that incorporate very small architecture within larger components has required the assembly of multiple elements to form a working device. Rapid, facile production of a working device using only a single layer of molded polydimethylsiloxane (PDMS) and a glass support substrate is achieved with the reported fabrication technique. A combination of conventional wet-chemical etching for larger (≥20 μm) microchannel features and focused ion beam (FIB) milling for smaller (≤10 μm) microwell features was used to fabricate a monolithic glass master mold. PDMS/glass hybrid chips were then produced using simple molding and oxygen plasma bonding methods. Microwell structures were loaded with 3 μm antibody-functionalized dye-encoded polystyrene spheres, and a sandwich immunoassay for common cytokines was performed to demonstrate proof-of-principle. Potential applications for this device include highly parallel multiplexed sandwich immunoassays, DNA/RNA hybridization analyses, and enzyme linked immunosorbent assay (ELISA). The fabrication technique described can be used for rapid prototyping of devices wherever submicrometer- to micrometer-sized features are incorporated into a microfluidic device.

Transport of biomolecules to binding partners displayed on the surface of microbeads arrayed in traps in a microfluidic cell

“…In other studies, wells at the floor of the microchannel are used to sequester and array microbeads to construct the probe library. 17,18,[22][23][24] In the well geometry, target only streams over the top part of the microbead, and at high Pe thin boundary layers cannot encircle a large portion of the microbead. As a result, diffusive transport is hindered, and one solution which is proposed is to create drains in the wells to enhance convection around the microbead.…”

“…Two common methods for arraying microbeads in a microfluidic cell are by using wells patterned into the bottom surface of the cell, e.g., Duffy et al 17 and Ramsey et al 18 or traps arranged as a microfluidic obstacle course, e.g., Nehorai et al 19,20 and our prior study on arraying lipobeads. 21 Well deposition has also been enhanced by using electric and magnetic fields to assist in the capture, [22][23][24] or by using holes placed in the well and connected to a drain to provide fluid suction (see McDevitt et al 25,26 and Ketterson 27 ).…”

Enabling Systems Biology Approaches Through Microfabricated Systems

“…To address this need, several devices have been developed that utilized hydrodynamic flow and physical obstacles 19,20 , dielectrophoresis 21,22 , microwells 23,24 , micropatterning 25 , acoustic waves 26 and droplet encapsulation 22,27–29 to precisely place individual cells in defined compartments and allow single cell measurements. Specifically, many groups have used a combination of carefully controlled flow and physically defined cell traps to offer an experimentally simple, passive and generalizable method of placing cells in defined physical locations 19,20,23 .…”

A large-area hemispherical perforated bead microarray for monitoring bead based aptamer and target protein interaction

“…11 Henley et al showed a microwell structure, which was fabricated by focused ion beam, and then, applied it for constructing the bead array to perform a sandwich immunoassay to analyze cytokines on the captured beads. 12 Sivagnanam et al reported in situ micropatterning of streptavidin-coated microbeads inside a microchannel using electrostatic self-assembly technique and used it for microbead based immunoassay to detect IgG antigen. 13 Burger et al presented a centrifugal microdevice for improving the microbead trap efficiency by implementing V-cup barriers in the channel.…”

“…16 Although the previous microbead array formats are adequate for sensitive biochemical analysis in a high-throughput manner without cross-contamination between beads, most of their designs were restricted to microwell structure. [8][9][10][11][12][13][14][15][16][17][18] Such a microwell structure mainly depends on the passive immobilization of the beads into each microwell, which is time-consuming, and suffers from the bead aggregate formation, leading to the non-uniform distribution of single beads in each chamber. In addition, the recovery of the immobilized beads is very difficult using the microwell array.…”