An unbounded approach to microfluidics using the Rayleigh–Plateau instability of viscous threads directly drawn in a bath

Abstract

We study the droplet-forming instability of a thin jet extruded from a nozzle moving horizontally below the surface of an isoviscous immiscible fluid bath. While this interfacial instability is a classic problem in fluid mechanics, it has never been studied in the context of the deposition of a thread into a reservoir, an open-sky version of microfluidics. As the nozzle translates through the reservoir, drops may form at the nozzle (dripping) or further downstream (jetting). We first focus on rectilinear printing paths and derive a scaling law to rationalize the transition between dripping and jetting. We then leverage the flexibility of our system and study the dynamics of breakup when printing sinusoidal paths. We unravel a methodology to control both the size of the drops formed by the instability and the distance that separates them.

Voxelated Bioprinting of Mechanically Robust Multiscale Porous Scaffolds for Pancreatic Islets

“…In the context of technology development, DASP is different from existing 3D printing techniques for manipulating spherical objects such as droplets and spheroids. For example, in embedded droplet printing, individual droplets are dispensed far apart from each other to form discrete patterns [17,40] or randomly stacked together to form thick structures [41] . By contrast, DASP enables on-demand deposition of individual bio-ink droplets at prescribed locations to form integrated, organized structures.…”

“…By contrast, DASP enables on-demand deposition of individual bio-ink droplets at prescribed locations to form integrated, organized structures. Moreover, DASP enables printing highly viscoelastic, non-Newtonian bio-inks in a cytocompatible environment; this contrasts with embedded droplet printing that relies on the interfacial tension between the immiscible aqueous and oil-like fluids to generate droplets, which, therefore, can handle low viscosity fluids only [17,40] . Compared to bioprinting of spheroids [18,42] where cells are often subject to direct mechanical manipulation, in DASP cells are encapsulated in a hydrogel matrix, which avoids possible high mechanical shear-induced cell damage.…”

Continuous Embedded Droplet Printing in Yield‐Stress Fluids for Pharmaceutical Drug Particle Synthesis

“…Because of these beneficial qualities, embedded droplet printing has demonstrated unique functionality in a wide variety of fluidic manipulation applications including chemical synthesis and screening, biological assays, and particle synthesis. There are many techniques for droplet generation and processing including open and off‐chip microfluidic systems, [ 13,14 ] in‐air microfluidics, [ 15 ] and droplet formation and deposition at a fluid interface. [ 16–19 ] However, embedded droplet printing is the only method (other than a microgravity environment) that allows for droplet processing in an “absolutely quiescent” state, namely the elimination of exterior convective forces as well as essentially indefinite spatial isolation of droplets from each other and from any boundaries of the bath material.…”

Direct-writing microporous polymer architectures – print, capture and release

“…14 In this paper, we demonstrate a breakthrough approach of fluid-on-fluid templating that addresses all of these challenges and enables rapid fabrication of functional, structured polymer films making these applications feasible and scalable. Extrusion of fluids within the bulk or on the surface of an elastomer matrix has been pioneered [18][19][20] to show the ability to capture and control functional materials in macro-scale patterns. Inspired by the BF method, we use the highly controlled, tuneable, direct-write benefits of drop-on-demand (DoD) inkjet printing to controllably print micron-scale droplets to a fluid surface, as illustrated in Fig.…”