High Density 3D Printed Microfluidics for Cell-Based Biomedical Applications - Project Summary
Concentration gradients of growth factors, other cell-signaling molecules, and nutrients drive a wide
range of critical biological processes, including immune cell migration, angiogenesis, wound healing,
cancer metastasis, and organism development. Microfluidic devices are extensively used to both create
the relevant concentration gradient, and to monitor cellular behavior in response to that gradient.
Unfortunately, most concentration gradient microfluidic devices are designed assuming exclusively
diffusional transport processes, while incorporating advective transport decoupling strategies that are
largely ineffective and/or slow. This approach results in specific and important drawbacks, including low
dynamic range in the gradient, unstable gradients over the lifetime of the measurement, and
inconsistency in the gradient between different spatial regions of the device. As a result, existing
microfluidic approaches to concentration gradient construction do not adequately mimic the diffusion-
generated concentration gradients found in-vivo. Hence, there is a large unmet need for microfluidic
devices that can rapidly create stable and flexible concentration gradients that allow sensitive
monitoring of critical cellular processes.
This renewal proposal focuses on leveraging and extending sophisticated high resolution 3D
printing technology for microfluidics to create integrated devices that generate concentration gradients
with large dynamic range that are switchable between multiple source and sink solutions with
selectable concentration and rapid set up time (few minutes) to enable temporal multiplexing of
sequences of stable concentration gradients. Research efforts will consist of three specific aims. First,
3D simulation will be employed to evaluate a wide range of concentration gradient formation
geometries based on a new opposing-flow concept for source and sink fluids with the objective of
decoupling advective from diffusive mass transport, where the former is needed to replenish source
and sink fluids while the latter is required to generate the concentration gradient. Next, a variety of
candidate geometries will be 3D printed and tested to iteratively optimize concentration gradient
dynamic range, set up time, stability, and uniformity. The best candidates will be integrated with on-chip
pumps, valves, serial diluters, and reservoirs to create integrated systems. Finally, such devices will be
used to analyze chemotaxis of metabolically engineered bacteria. The new capabilities developed over
the grant period are designed to allow important questions to be answered with respect to
developmental biology, cellular response to nutritive cues, as well as angiogenesis, and cancer growth
and invasiveness.
