Chaotic mixing in three-dimensional microvascular networks fabricated by direct-write assembly

Abstract

The creation of geometrically complex fluidic devices is a subject of broad fundamental and technological interest. Here, we demonstrate the fabrication of three-dimensional (3D) microvascular networks through direct-write assembly of a fugitive organic ink. This approach yields a pervasive network of smooth cylindrical channels (approximately 10-300 microm) with defined connectivity. Square-spiral towers, isolated within this vascular network, promote fluid mixing through chaotic advection. These vertical towers give rise to dramatic improvements in mixing relative to simple straight (1D) and square-wave (2D) channels while significantly reducing the device planar footprint. We envisage that 3D microvascular networks will provide an enabling platform for a wide array of fluidic-based applications.

Structural reinforcement of microvascular networks using electrostatic layer-by-layer assembly with halloysite nanotubes

“…Scaffold preparation: Fugitive scaffolds were assembled by the direct-write process as detailed by Therriault et al 27 Ink loaded into pressurized syringes was pattern-deposited onto substrates using a robotic positioning platform (Aerotek) building a planar line pattern, then building a second layer above that and repeating to yield a three-dimensional scaffold. Multilayers were assembled onto scaffolds by alternating immersion in aqueous solutions/dispersions of 10 -2 M PDADMAC and 1mg/mL halloysite with three intermediate Milli-Q pure rinse baths in a Stratosequence6 (Nanostrata, Inc.) dipper.…”

“…7,8,[23][24][25][26] Our research group has studied networks made using direct-write assembly, in which a hydrocarbon microcrystalline wax is extruded to form the scaffold using robotically controlled deposition. 27 With appropriate methods of scaffold fabrication, the advantage of this second method is greater control over network design as channels can have non-linear shapes and linkages, but due to the absence of load-bearing glass fibers these materials experience a reduction in bulk mechanical properties. When subjected to high loads, unreinforced microchannels can provide paths for crack propagation and act as strain concentrators leading to microcrack nucleation.…”

“…Using direct-write assembly, Therriault et al have fabricated templates using robotic deposition of a fugitive microcrystalline wax in order to make self-healing microvascular materials. 27 Preliminary research suggests that these scaffold-based networks are strengthened by the addition of an alumina microparticle layer to the surface of the scaffold before prepolymer infiltration, thus transferring reinforcing layer onto the epoxy network channel walls. Fluorescence-based digital image correlation (FDIC) measurements of single channels in cross-section have shown a significant reduction in strain concentrations around surface-modified channels suggesting increased stress tolerance.…”

Design and additive manufacture for flow chemistry

“…116 The group used an additive process known as direct write assembly to fabricate a network of smooth cylindrical channels (~ 10-300 µm). The direct write assembly manufacturing process begins with the deposition of an organic ink onto a moving X-Y build platform.…”

Ultrafast active mixer using polyelectrolytic ion extractor

“…26 The zig-zag-shaped channel mixers require a relatively high Reynolds number (>80), whereas the mixers based on a modified Telsa structure exhibit good mixing efficiency even at a relatively low Reynolds number (>5) owing to the Coanda effect. Reports of 3D serpentine structures 28, 31 have also been published with various designs, most of which need the Reynolds number to be higher than 10 and the channels longer than 10 mm. Stroock et al made staggered herringbone patterned grooves on a channel wall to generate chaotic advection and obtained good mixing performance over a wide range of Reynolds numbers (1 < Re <100).…”