Nicholas Scott Lynn Jr., Ph.D.

In brief, I work with microfluidic systems. These fluidic systems simply move liquids (sometimes gases) around from one place to another, and in some cases are simply like those you’d find in your kitchen, in other cases like those in an oil refinery - however, they are much smaller. Some you might see with your eyes, albeit poorly, and others require a powerful microscope to see.
I am not only interested in how we can manipulate fluids to flow precisely in such small systems, but more importantly, how fast the components of such fluids are transported around the fluid itself, and how quickly they might interact with a surface.
A bit wordier, I am interested in the design of microfluidic and nanofluidic systems for applications in catalysis, surface science, chemistry, and biosensing. Specified by individual fields, my research interests are in the areas of microfluidics, fluid dynamics and transport phenomena, computational fluid dynamics, mixing, microfabrication and nanofabrication, 3D printing, biosensing, biophysics, biomolecular interactions, catalysis, reactor design, and polymer chemistry.
Some of our recent research projects are detailed below.
3D printed flow cells for the mass synthesis of polymer brush interfaces.
We research how simple, 3D printed parts can be used for the synthesis of polymer brush films onto a variety of planar substrates (glass, silicon, gold) used for biosensing and biological studies. These polymer brush films are used by the Laboratory of Functional Biointerfaces as an antifouling biointerface coating for a variety of biosensors, typically those based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM). To maintain their antifouling properties, these polymer brush films must be very dense (i.e., individual polymer chains are very close to one another) and homogenous (i.e., all chains have similar lengths). The most effective method to synthesize dense and homogenous polymer brush films is surface-initiated atom transfer radical polymerization (SI-ATRP), a heterogeneous catalytic method based on the growth of individual polymer chains from initiators that are immobilized to a surface (Figure 1).
Figure 1: Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) for the synthesis of a polymer brush composed of carboxybetaine methacrylamide (CBMAA), a zwitterionic monomer having antifouling properties that can be functionalized with bioreceptors for a biosensing process.
One of the main drawbacks of the SI-ATRP is its efficiency: substrates must be immersed in a solution containing catalyst (with an appropriate ligand) and monomer, the latter in relatively high concentrations, where the entire process must be carried out under oxygen-free conditions. This becomes somewhat problematic in biosensing (and other fields), which often require 10-100 polymer-coated substrates every day. Even under optimal conditions, a standard SI-ATRP synthesis results in less than 1:10,000 monomers in solution being polymerized onto the substrate. In such cases the high cost of monomers becomes prohibitive.
To alleviate this, we have recently explored the use of simple 3D printed flow cells for the mass synthesis of polymer brush films. We started with the knowledge gained with the use of a single flow cell (having a total fluidic volume of less than 10 μL) to design a series of components that, when stacked together, form a continuous fluidic pathway connecting a variable number of substrates, depending on the number of stacked layers put together. Such a microfluidic stack reactor (Figure 2) serves not only to reduce the dead volume of a polymerization by over 100×, but was also shown to synthesize polymer brush films that were more dense with respect to those prepared via standard means.
A preprint of this work can be viewed here.
Figure 2: Microfluidic stack reactors for the mass synthesis of polymer brush films. The top side of each individual layer is designed to accommodate and align a single substrate, where the bottom side maintains a gasket that seals to the substrate on the layer below. When stacked together, where each layer is rotated 180 degrees with respect to the layer above, this arrangement maintains a single fluidic pathway connecting each substrate.