Browsing by Author "LeFevre, Thomas B."

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Coupling fluid flow to hydrogel fluidic devices with reversible “pop-it” connections
(Royal Society of Chemistry, 2021-01) Abbasi, Reha; LeFevre, Thomas B.; Benjamin, Aaron D.; Thornton, Isaak J.; Wilking, James N.
Here, we describe a simple, reversible, plug-based connector designed to couple microfluidic tubing to a hydrogel-based fluidic device, to allow for pressurized liquid flow through the system.
An inexpensive, versatile, compact, programmable temperature controller and thermocycler for simultaneous analysis and visualization within a microscope
(Springer Science and Business Media LLC, 2021-05) Cruz, Pablo Martínez; Wood, Mikayla A.; Abbasi, Reha; LeFevre, Thomas B.; McCalla, Stephanie E.
Microfluidic Lab on a Chip (LOC) devices are key enabling technologies for research and industry due to their compact size, which increases the number of integrated operations while decreasing reagent use. Common operations within these devices such as chemical and biological reactions, cell growth, or kinetic measurements often require temperature control. Commercial temperature controllers are constrained by cost, complexity, size, and especially versatility for use in a broad range of applications. Small companies and research groups need temperature control systems that are more accessible, which have a wide applicability. This work describes the fabrication and validation of an inexpensive, modular, compact, and user-friendly temperature control system that functions within a microscope. This system provides precise temperature acquisition and control during imaging of any arbitrary sample which complies with the size of a microscope slide. The system includes two parts. The first part is a compact and washable Device Holder that is fabricated from high temperature resistant material and can fit securely inside a microscope stage. The second part is a robust Control Device that incorporates all the necessary components to program the temperature settings on the device and to output temperature data. The system can achieve heating and cooling times between 50°C and 100°C of 32 seconds and 101 seconds, respectively. A Bluetooth enabled smartphone application has been developed for real-time data visualization. The utility of the temperature control system was shown by monitoring rhodamine B fluorescence in a microfluidic device over a range of temperatures, and by performing a polymerase chain reaction (PCR) within a microscope. This temperature control system could potentially impact a broad scope of applications that require simultaneous imaging and temperature control.
Light-Based 3D Printing of Hydrogels with High-Resolution Channels
(2019-01) Benjamin, Aaron D.; Abbasi, Reha; Owens, Madison; Olsen, Robert J.; Walsh, Danica J.; LeFevre, Thomas B.; Wilking, James N.
Hydrogels are soft, water-based gels with widespread applications in personal care products, medicine and biomedical engineering. Many applications require structuring the hydrogel into complex three-dimensional (3D) shapes. For these applications, light-based 3D printing methods offer exquisite control over material structure. However, the use of these methods for structuring hydrogels is underdeveloped. In particular, the ability to print hydrogel objects containing internal voids and channels is limited by the lack of well-characterized formulations that strongly attenuate light and the lack of a theoretical framework for predicting and mitigating channel occlusion. Here we present a combined experimental and theoretical approach for creating well-defined channels with any orientation in hydrogels using light-based 3D printing. This is achieved by the incorporation of photoblocker and the optimization of print conditions to ensure layer-layer adhesion while minimizing channel occlusion. To demonstrate the value of this approach we print hydrogels containing individual spiral channels with centimeter-scale length and submillimeter-scale cross-section. While the channels presented here are relatively simple, this same approach could be used to achieve more complex channel designs mimicking, for example, the complex vasculature of living organisms. The low cytotoxicity of the gel makes the formulation a promising candidate for biological applications.