Non-spherical particle generation from 4D optofluidic fabrication

Abstract

Particles with non-spherical shapes can exhibit properties which are not available from spherical shaped particles. Complex shaped particles can provide unique benefits for areas such as drug delivery, tissue engineering, structural materials, and self-assembly building blocks. Current methods of creating complex shaped particles such as 3D printing, photolithography, and imprint lithography are limited by either slow speeds, shape limitations, or expensive processes. Previously, we presented a novel microfluidic flow lithography fabrication scheme combined with fluid inertia called optofluidic fabrication for the creation of complex shaped three-dimensional (3D) particles. This process was able to address the aforementioned limits and overcome two-dimensional shape limitations faced by traditional flow lithography methods; however, all of the created 3D particle shapes displayed top-down symmetry. Here, by introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles where we termed the process: four-dimensional (4D) optofluidic fabrication. This 4D optofluidic fabrication is comprised of three sequential procedures. First, density mismatched precursor fluids flow past pillars within fluidic channels to manipulate the flow cross sections via fluid inertia. Next, the time dimension is incorporated by stopping the flow and allowing the denser fluids to settle by gravity to create asymmetric flow cross sections. Finally, the fluids are exposed to patterned ultraviolet (UV) light in order to polymerize fully asymmetric 3D-shaped particles. By varying inertial flow shaping, gravity-induced flow shaping, and UV light patterns, 4D optofluidic fabrication can create an infinite set of complex shaped asymmetric particles.

Automated Design for Microfluid Flow Sculpting: Multiresolution Approaches, Efficient Encoding, and CUDA Implementation

“…With an experimentally identified set of four micropillar diameters and eight lateral positions in the channel (for a total of 32 different micropillar configurations, which are easily manufacturable), a variety of possible fluid flow shape transformations have been predicted and experimentally validated for an inlet configuration [2]. These manually designed micropillar sequences have since been used to tailor polymer fiber cross sections [7], create 3D particles [8][9][10], and for solution transfer around particles in flow [11]. Such applications are still quite fundamental and broad in their scope, and the full potential of pillar programming in research and industry remains untapped.…”

DIY 3D Microparticle Generation from Next Generation Optofluidic Fabrication

“…When a new particle shape is needed, a new channel with a different pillar configuration is required. Thus, instead of preparing new channels either by photolithography or 3D printing, [10,15] NG-OF uses an on-the-fly approach that creates pillars at a desired channel location by local UV polymerization (see Figure 4a and more details below) that is used for creating 3D-shaped microparticles.As mentioned, NG-OF is based on inertial flow shaping from our previous optofluidic fabrication. [10] Figure 1a shows Complex-shaped microparticles can enhance applications in drug delivery, tissue engineering, and structural materials, although techniques to fabricate these particles remain limited.…”

Computational methods and software for the design of inertial microfluidic flow sculpting devices

“…With an experimentally identified set of 4 micropillar diameters and 8 lateral positions in the channel (for a total of 32 different micropillar configurations, which are easily manufacturable), a variety of possible fluid flow shape transformations have been predicted and experimentally validated for an inlet configuration (Stoecklein et al, 2014). These manually designed micropillar sequences have since been used to tailor polymer fiber cross-sections (Nunes et al, 2014), create 3-D particles (Paulsen et al, 2015;Wu et al, 2015;Paulsen and Chung, 2016), and for solution transfer around particles in flow (Sollier et al, 2015). Such applications are still quite fundamental and broad in their scope, and the full potential of pillar programming in research and industry remains untapped.…”

“…Flow sculpting via pillar sequences has since been applied to problems in biological and advanced manufacturing fields. For example, polymer precursors can create shaped microfibers and particles (Nunes et al, 2014;Paulsen et al, 2015;Paulsen and Chung, 2016;Wu et al, 2015), and a pillar sequence can shift fluid streams away from cells in flow (Sollier et al, 2015).…”

“…The symmetry of fluid flow shapes is a natural result of the deformation induced by pillars which span the height of the channel, since there is mirror symmetry across the horizontal midline of the channel. Paulsen and Chung proposed a novel method of obviating this limitation for the fabrication of non-spherical particles (Paulsen and Chung, 2016): mismatched densities of the sculpted fluid and sheath flow would be given time for gravitationally-driven settling to break symmetry before polymerizing the fluid into particles. This method comes with several clear drawbacks.…”