Scanning two-photon continuous flow lithography for synthesis of high-resolution 3D microparticles

Abstract

Demand continues to rise for custom-fabricated and engineered colloidal microparticles across a breadth of application areas. This paper demonstrates an improvement in the fabrication rate of high-resolution 3D colloidal particles by using two-photon scanning lithography within a microfluidic channel. To accomplish this, we present (1) an experimental setup that supports fast, 3D scanning by synchronizing a galvanometer, piezoelectric stage, and an acousto-optic switch, and (2) a new technique for modifying the laser's scan path to compensate for the relative motion of the rapidly-flowing photopolymer medium. The result is an instrument that allows for rapid conveyor-belt-like fabrication of colloidal objects with arbitrary 3D shapes and micron-resolution features.

FlowSculpt: software for efficient design of inertial flow sculpting devices

“…Eventually, the uFlow and FlowSculpt may merge into a single software, but their current architectures have different intent from the ground-up: uFlow for visualization (with little regard for efficiency), and FlowSculpt for optimization (which would be encumbered by uFlow's processes), making integration complex and a low-priority goal. Beyond these developments in the software, FlowSculpt itself can be brought into other regimes of hierarchical design, such as tailored 3D particles via stop-flow lithography, 4,6 transient liquid molding, 5 or continuous-flow lithography, 14 enabling a new class of complex microfluidic engineering. We also anticipate that FlowSculpt will find more general use in engineering flow streams as more disciplines become aware of its capability, especially in manipulating material concentrations or distributions in microfluidic flow applications.…”

“…Many current applications of flow sculpting were devised and implemented by inertial microfluidics experts, and even then, they sculpted relatively simple flow shapes that were achieved through trial-and-error design. A clear example of this difficulty is particle fabrication via flow sculpting, which remains competitive with state-of-the-art methods such as PRINT, 12 SEAL, 13 two-photon lithography, 14 and hollow fiber templating 15 due to the ability to create multi-material shaped 3D particles at high-throughput using basic microfluidic tools such as soft lithography 16 and 3D printing. 6 However, the flow sculpting approaches currently require the target 3D particle shape to comprise of the intersection of two orthogonally extruded 2D shapes: one from the shape of the sculpted flow stream (which contains a polymer precursor with a photoinitiator), and the other from an optical mask (which shapes polymerizing ultraviolet light).…”

Formation of uniform reaction volumes using concentric amphiphilic microparticles

“…[16,17] In addition, spherical particles have more limited barcoding options, and it has been reported that the presence of surfactants leads to higher rates of transport of products of reactions through the continuous oil phase, reducing sensitivity of enzymatic assays. [18,19] A range of fabrication methodologies have been explored over the past decade to create particles with different shapes and functionalities using continuous [20][21][22][23][24] or stop flow lithography techniques [25][26][27][28] combined with hydrodynamic focusing, [29][30][31][32] magnetically tunable color printing, [12,33] vertical flows, [34] structured hollow fibers [35] or inertial forces. [36][37][38][39] Particles comprised of layers of hydrophobic and hydrophilic materials were shown to selectively interact and assemble around aqueous drops.…”

Shape design for stabilizing microparticles in inertial microfluidic flows

“…Singh, Koch & Stroock (2013) identified ring-shaped particles which do not tumble in shear flow, in contrast to the tumbling behaviour of axisymmetric particles reported by numerous earlier works; the particle shapes were derived as perturbations to a circular shape to obtain zero torques on the particle. Uspal & Doyle (2014) designed self-aligning and centreline-focusing characteristics of asymmetric particles in Hele- Shaw flowspecifically, 'dumbbell' and 'trumbbell' shapes. Further motivating study of the inverse problem in fluid particle systems is the rapidly developing capabilities of particle fabrication techniques (Paulsen 2017;Shaw et al 2018;Yuan et al 2018;Wu et al 2018). These approaches enable scalable fabrication of arbitrary-shaped microparticles, presenting an abundant landscape for the design of customized microparticles for applications in biosensing and self-assembly.…”