Author
Paulsen, Kevin
Other Contributors
Chung, Aram; Hirsa, Amir H.; Underhill, Patrick T.; Walczyk, Daniel F.;
Date Issued
2017-12
Subject
Mechanical engineering
Degree
PhD;
Terms of Use
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.;
Abstract
Next, a modification of optofluidic fabrication is introduced to break the top-down symmetry observed in all of the original 3D particle shapes. By introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles with a process termed Four-dimensional (4D) optofluidic fabrication. After pillar induced inertial flow shaping, the time dimension is incorporated by stopping the flow and allowing denser UV-reactive fluids to settle by gravity to create asymmetric flow cross-sections. Patterned UV light illumination then polymerizes fully asymmetric 3D particles. In order to maximize the generated particle utility, a solution is then presented to enable sub-100 micron particle generation by adding a tapered reduction channel after pillar-induced inertial flow shaping that reduces the channel size 10-fold. 3D particles with dimensions 50 x 35 x 30 µm3 and minimum feature sizes of 15 µm are shown. All experimental results involving inertial flow shaping are compared to and validated with finite element based simulations. Although a limited number of particles are presented, by adjusting flow rates, pillar configurations, and photomasks, an infinite set of particle shapes are possible.; Complex shaped particles have shown great potential for applications such as drug delivery, tissue engineering, and structural materials; however, the ability to fabricate custom particle shapes with current manufacturing methods remains limited. A variety of techniques can create two-dimensional shaped particles such as cubes and cylinders, although it is expected that fully three-dimensional (3D) shaped particles can enhance their utility due to increased surface-area-to-volume ratios and altered structural properties. Here, we present a novel inertial microfluidic technology called optofluidic fabrication for the generation of complex 3D-shaped polymer particles based on two coupled processes: inertial flow shaping and ultraviolet light (UV) polymerization. While flowing at finite Reynolds numbers in microfluidic channels, secondary flows generated near pillars within the channel deterministically alter the flow cross-section of UV-reactive and inert fluid streams coflowing through the channel. The channels are then illuminated with patterned UV light to polymerize the UV curable fluid, creating particles with multi-scale 3D geometries. The effect of pillar location, number of pillars, Reynolds number, and photomask pattern is investigated for the creation of a variety of 3D particle shapes at the millimeter scale.;
Description
December 2017; School of Engineering
Department
Dept. of Mechanical, Aerospace, and Nuclear Engineering;
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Relationships
Rensselaer Theses and Dissertations Online Collection;
Access
Restricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.;