3D shape evolution of microparticles and 3D enabled applications using non-uniform UV flow lithography (NUFL)

Abstract

The generation of microparticles with non-spherical morphologies has generated extensive interest because of their enhanced physical properties that can increase their performance in a wide variety of clinical and industrial applications. A flow lithographic technique based on stop flow lithography (SFL) recently showed the ability to fabricate particles with 3D shapes via manipulation of the UV intensity profile in a simple 2D microfluidic channel. Here, we further explore this flow lithographic method, called non-uniform flow lithography (NUFL), to investigate the 3D-shape tuning ability for the generation of 3D magnetic microparticles and their potential applications. We characterize the morphological microparticle shape change through variation of polymerization objective, UV intensity, and solution opacity. We also couple the particles' intrinsic anisotropic magnetic properties with an external magnetic field to create chains of bullet- and bell-shaped particles and a valve-like micromachine. In addition, in contrast to other complex and multi-step methodologies, NUFL shows a simple route for the facile creation of 3D microstructure platforms such as microneedles with fully modifiable tip morphology. This method presents intriguing possibilities for growing research within 3D microstructure assembly, micromachine systems and minimally invasive medical interventions.

Microparticles, Microspheres, and Microcapsules for Advanced Drug Delivery

“…Magnetic nanoparticles embedded into nonplanar, bullet-shaped microneedles give access to mild invasive therapy [9].…”

“…The monomer solution is pumped through a microfluidic device, where photopolymerization occurs. The polymer particles (sometimes of extreme shape) are collected after having left the device [9,119] and have been used for the controlled synthesis of bullet-shaped, 12.4µm long, magnetic and non-magnetic microparticles using stop-flow lithography, which gives the possibility of executing mild invasive drug delivery via microneedles. Wu et al [96] demonstrated that in the case of monodisperse rifampicin-PLGA core-shell microcapsules, the burst-release can be decreased with increased encapsulation efficiency, and the release can be controlled by increasing the wall thickness.…”

From shaping to functionalization of micro-droplets and particles

“…Recently, a modied ow lithography technique was proposed for the synthesis of microparticles with 3D anisotropy beyond 2D extruded shapes. [147][148][149] Habasaki et al presented vertical ow lithography (VFL), an application of stereolithography concepts to conventional ow lithography, which allowed better control over the fabrication of 3D anisotropic microparticles. 150 In VFL, the light exposure and photocurable resin ow directions were aligned to enable the stacking of multiple photopolymerized layers with controlled 2D shape and thickness (Fig.…”

Designable 3D Microshapes Fabricated at the Intersection of Structured Flow and Optical Fields

“…While flow‐lithography based particle fabrication, in which photocurable polymers are flowed through a microfluidic chip and polymerized by UV light passing through a photomask, has shown to have excellent control of particle shape along a single 2D extrusion axis, a similar level of shape control in the direction of flow is yet to be achieved . In recent years, there have been efforts to improve the complexity of particles beyond 2D extruded shapes through techniques such as hydrodynamic flow shaping and nonuniform flow lithography . However, the mechanisms enabling these methods, or inertial focusing and nonuniform UV light intensity, are not precise and are difficult to control, limiting particle shape design freedom.…”