Scalable Generation of Strictly Monodisperse Droplets by Transverse Electrohydrodynamic Excitations

Duan, Hongxu; Yang, Weiwei; Li, Cheng; Lojewski, Brandon; Deng, Weiwei

doi:10.1080/02786826.2013.829208

Cited by 4 publications

(2 citation statements)

References 16 publications

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“…3b, produce droplets with radius CV of 0.5%. These droplets are more monodisperse than those produced through other recently developed methods, which all report polydispersity > 1% [7,12,13,14,16,17,18,19,20]. It should be noted that our measurement of droplet radius CV is limited by the precision with which we are able to measure individual droplet radii (∼ 60 nm), and so the quoted value represents an upper bound on the actual radius CV.…”

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confidence: 82%

Snap-off production of monodisperse droplets

2015

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Abstract. We introduce a novel technique to produce monodisperse droplets through the snap-off mechanism. The methodology is simple, versatile, and requires no specialized or expensive components. The droplets produced have polydispersity < 1% and can be as small as 2.5 µm radius. A convenient feature is that the droplet size is constant over a 100-fold change in flow rate, while at higher flows the droplet size can be continuously adjusted.Microfluidics applications often require emulsions with a wide range of characteristics, prompting the development of several distinct techniques for producing droplets [1,2]. One important parameter is the degree of polydispersity among droplet sizes, where smaller values are preferable for many applications. Droplets with an extremely low polydispersity are particularly desirable for basic science investigations of emulsions [3,4], vessels for tiny experiments [5,6,7], as well as calibration in both academic and industrial settings [8]. Here we present a method we have recently developed using glass capillaries and a surface tension driven 'snap-off' instability to produce droplets. This method is remarkable for its simplicity, ease of implementation, and the high monodispersity of droplets produced. An additional convenience is that there are two distinct regimes of droplet production: 1) the size of droplets is insensitive at low flow rates; while, 2) at high flow rates the droplet size is tunable.The snap-off instability of droplets in cylindrically symmetric capillaries was first described in 1970 [9], and has since been investigated further in the context of understanding the physics behind snap-off [10,11]. We took advantage of this effect to develop a versatile system for production of monodisperse droplets that is easy to assemble and operate. One important consideration is that this setup requires no flow of the continuous phase, since the pinch-off is driven by surface tension forces rather than viscous forces. Although the snap-off process has been used previously to produce droplets in flattened microfluidic geometries [12,13,14], our simple cylindrical configuration is able to produce droplets that are more monodisperse.In order to prepare monodisperse droplets we have utilised a method that is schematically depicted in Fig.

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confidence: 82%

Snap-off production of monodisperse droplets

2015

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“…Nanoscale P3HT structures were formed on PEDOT:PSS/Si substrates by electrospray deposition of the polymer solution. Electrospray (Figure ) atomized liquids and solutions into uniform‐diameter sub‐micrometer droplets with typical relative standard deviation of ≈10% . The electrospray source was a blunt stainless steel nozzle with 410 µm outer diameter and 200 µm inner diameter.…”

Section: Methodsmentioning

confidence: 99%

Nanostructured Semiconducting Polymer Films with Enhanced Crystallinity and Reorientation of Crystalline Domains by Electrospray Deposition

Zhao

Johnston

Rodriguez

et al. 2017

Macro Materials & Eng

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Self‐organization of conjugated polymer such as poly(3‐hexylthiophene) (P3HT) causes directional anisotropy in the charge carrier mobility. In contrast to an edge‐on orientation formed in thin films of P3HT made by spin coating, in this study electrospray deposition rotates the orientation while producing nanopillar structures as a result of Coulombic fission and significant evaporation of solvent from the droplets. The nanostructured films are investigated by scanning electron microscopy. Due to substantial polymer–air interfaces oriented perpendicular to the substrate, P3HT molecules adopt a face‐on orientation with respect to the substrate plane that is confirmed by grazing incidence X‐ray diffraction. Additionally, enhanced crystallinity (29% increase) is confirmed by a redshift in the UV–vis absorption spectra. Because deposition by electrospray is a scalable nanomanufacturing method, these results inform the design of low‐cost device layers for large‐surface‐area applications such as light emitting diodes and photovoltaics.

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