Gaseous flow focusing for spinning micro and nanofibers

Ponce-Torres, A.; Ortega, Eduardo; Rubio, M.; Rubio, Alejandro; Vega, E. J.; Montanero, J. M.

doi:10.1016/j.polymer.2019.121623

Cited by 17 publications

(14 citation statements)

References 20 publications

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“…More recently, the same principle has been applied to form viscoelastic threads [236,420] for smooth printing and bioplotting [237], and to fabricate fibers with diameters ranging from a few microns down to hundreds of nanometers [421,422] (Fig. 46).…”

Section: Flow Focusing Applicationsmentioning

confidence: 99%

Dripping, jetting and tip streaming

2020

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Dripping, jetting and tip streaming have been studied up to a certain point separately by both fluid mechanics and microfluidics communities, the former focusing on fundamental aspects while the latter on applications. Here, we intend to review this field from a global perspective by considering and linking the two sides of the problem. In the first part, we present the theoretical model used to study interfacial flows arising in droplet-based microfluidics, paying attention to three elements commonly present in applications: viscoelasticity, electric fields and surfactants. We review both classical and current results about the stability of jets affected by these elements. Mechanisms leading to the breakup of jets to produce drops are reviewed as well, including some recent advances in this field. We also consider the relatively scarce theoretical studies on the emergence and stability of tip streaming in open systems. In the second part of this review, we focus on axisymmetric microfluidic configurations which can operate on the dripping and jetting modes either in a direct (standard) way or via tip streaming. We present the dimensionless parameters characterizing these configurations, the scaling laws which allow predicting the size of the resulting droplets and bubbles, as well as those delimiting the parameter windows where tip streaming can be found. Special attention is paid to electrospray and flow focusing, two of the techniques more frequently used in continuous drop production microfluidics. We aim to connect experimental observations described in this section of topics with fundamental and general aspects described in the first part of the review. This work closes with some prospects at both fundamental and practical levels.

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Section: Flow Focusing Applicationsmentioning

confidence: 99%

Dripping, jetting and tip streaming

2020

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“…In the solution, the polymer concentration is a critical parameter that strongly influences the liquid’s rheology due to stearic conformation and interaction of the polymer chains, thus resulting in formation of coils. Other methods for processing of polymer solutions include melt blow, flow focusing, and liquid atomization strategies [ 11 , 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

On the Ejection of Filaments of Polymer Solutions Triggered by a Micrometer-Scale Mixing Mechanism

et al. 2021

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Polymer filaments constitute precursor materials of so-called fiber mats, ubiquitous structures across cutting-edge technological fields. Thus, approaches that contribute to large-scale production of fibers are desired from an industrial perspective. Here, we use a robust liquid atomization device operated at relatively high flow rates, ~20 mL/min, as facilitating technology for production of multiple polymer filaments. The method relies on a turbulent, energetically efficient micro-mixing mechanism taking place in the interior of the device. The micro-mixing is triggered by radial implosion of a gas current into a liquid feeding tube, thus resulting in breakup of the liquid surface. We used poly(ethylene oxide) solutions of varying concentrations as test liquids to study their fragmentation and ejection dynamics employing ultra-high speed imaging equipment. Taking an energy cascade approach, a scaling law for filament diameter was proposed based on gas pressure, liquid flow rate and viscosity. We find that a filament dimensionless diameter, Df*, scales as a non-dimensional liquid flow rate Q* to the 1/5. The study aims to elucidate the underlying physics of liquid ejection for further applications in material production.

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“…Further processing leads to reduction of the cross section of the jet or filaments down to a size where solvent rapidly evaporates and the polymer solidifies, thus resulting in microfibers. The entire process usually occurs in a time scale of milliseconds and, in most widespread techniques, is driven by a combination of mechanical and electrical forces. − Noticeably, the driving force should be sufficiently strong to overcome capillary forces, such as surface tension, which promote breakup of the jet or filament into droplets. The interplay of forces influencing the fiber formation may be evaluated by the Ohnesorge (Oh) number, a dimensionless quantity representing the ratio of viscous to inertial forces where ρ l is the density of the liquid; R is a characteristic length scale (typically the radius of the jet or filament); and μ and σ are the solution’s viscosity and surface tension, respectively.…”

Section: Introductionmentioning

confidence: 99%

Micromixing with In-Flight Charging of Polymer Solutions in a Single Step Enables High-Throughput Production of Micro- and Nanofibers

Modesto-López

Olmedo-Pradas

2022

ACS Omega

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Controlled ejection of liquids at capillary scales is a ubiquitous phenomenon associated with significant advances in, for instance, molecular biology or material synthesis. In this work, we introduce a high-throughput approach, which relies on a micromixing mechanism to eject and fragment viscous liquids, for production of microfibers from poly(vinyl alcohol) solutions. First, filaments were generated pneumatically with a so-called flow-blurring atomizer and using liquid flow rates of up to ∼1 L/min. Subsequently, the filaments were ionized online by corona discharge and consecutively manipulated with an electric field created by disc electrodes. Such charging of the filaments and the effect of the electric field allowed for their ultrafast elongation and diameter reduction from 150 μm down to fibers of 500 nm, which after collection exhibited fabric-like texture. The approach presented herein is a general procedure with potential for scalability that, upon proper adaptation, may be extended to various polymeric materials.

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Gaseous flow focusing for spinning micro and nanofibers

Cited by 17 publications

References 20 publications

Dripping, jetting and tip streaming

Dripping, jetting and tip streaming

On the Ejection of Filaments of Polymer Solutions Triggered by a Micrometer-Scale Mixing Mechanism

Micromixing with In-Flight Charging of Polymer Solutions in a Single Step Enables High-Throughput Production of Micro- and Nanofibers

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