Pieter Oomen

Fused Deposition Modeling 3D Printing for (Bio)analytical Device Fabrication: Procedures, Materials, and Applications

In this work, the use of fused deposition modeling (FDM) in a (bio)analytical/lab-on-a-chip research laboratory is described. First, the specifications of this 3D printing method that are important for the fabrication of (micro)devices were characterized for a benchtop FDM 3D printer. These include resolution, surface roughness, leakage, transparency, material deformation, and the possibilities for integration of other materials. Next, the autofluorescence, solvent compatibility, and biocompatibility of 12 representative FDM materials were tested and evaluated. Finally, we demonstrate the feasibility of FDM in a number of important applications. In particular, we consider the fabrication of fluidic channels, masters for polymer replication, and tools for the production of paper microfluidic devices. This work thus provides a guideline for (i) the use of FDM technology by addressing its possibilities and current limitations, (ii) material selection for FDM, based on solvent compatibility and biocompatibility, and (iii) application of FDM technology to (bio)analytical research by demonstrating a broad range of illustrative examples.

Bisecting Microfluidic Channels with Metallic Nanowires Fabricated by Nanoskiving

This paper describes the fabrication of millimeter-long gold nanowires that bisect the center of microfluidic channels. We fabricated the nanowires by nanoskiving and then suspended them over a trench in a glass structure. The channel was sealed by bonding it to a complementary poly(dimethylsiloxane) structure. The resulting structures place the nanowires in the region of highest flow, as opposed to the walls, where it approaches zero, and expose their entire surface area to fluid. We demonstrate active functionality, by constructing a hot-wire anemometer to measure flow through determining the change in resistance of the nanowire as a function of heat dissipation at low voltage (<5 V). Further, passive functionality is demonstrated by visualizing individual, fluorescently labeled DNA molecules attached to the wires. We measure rates of flow and show that, compared to surface-bound DNA strands, elongation saturates at lower rates of flow and background fluorescence from nonspecific binding is reduced.

How microtechnologies enable organs-on-a-chip

Engineering cellular microenvironments that more accurately reflect the in vivo situation is now recognized as being crucial for the improvement of the in vitro viability and in vivo-like function of cells or tissues. Microfluidic technologies have been increasingly applied since the late 1990s for this purpose, with a growing number of examples of perfused cell and tissue cultures in microfluidic chambers and channels. More recently, additional microfabricated features have been implemented in microfluidic structures to achieve 3-D cell culture systems which mimic not only in vivo fluid flows, but also the structure, transport, and mechanical properties of tissue in, for example, the lung or the intestine. The ultimate challenge becomes the combination of different organ functions into single, linked-compartment devices - the body-on-the-chip.