We numerically investigate the rheological response of a noncoalescing multiple emulsion under a symmetric shear flow. We find that the dynamics significantly depends on the magnitude of the shear rate and on the number of the encapsulated droplets, two key parameters whose control is fundamental to accurately select the resulting nonequilibrium steady states. The double emulsion, for instance, attains a static steady state in which the external droplet stretches under flow and achieves an elliptical shape (closely resembling the one observed in a sheared isolated fluid droplet), while the internal one remains essentially unaffected. Novel nonequilibrium steady states arise in a multiple emulsion. Under low/moderate shear rates, for instance, the encapsulated droplets display a nontrivial planetarylike motion that considerably affects the shape of the external droplet. Some features of this dynamic behavior are partially captured by the Taylor deformation parameter and the stress tensor. Besides a theoretical interest on its own, our results can potentially stimulate further experiments, as most of the predictions could be tested in the lab by monitoring droplets’ shapes and position over time.
We present a multilayer dropmaker geometry that enables the modular fabrication of microfluidic devices containing precisely patterned channel surface wettability. The platform is used for the scalable production of uniform double emulsion drops. , Microfluidic devices enable the production of uniform double emulsions with control over droplet size and shell thickness. However, the limited production rate of microfluidic devices precludes the use of monodisperse double emulsions for industrial-scale applications, which require large quantities of droplets. To increase throughput, devices can be parallelized to contain many dropmakers operating simultaneously in one chip, but this is challenging to do for double emulsion dropmakers. Production of double emulsions requires dropmakers to have both hydrophobic and hydrophilic channels, requiring spatially precise patterning of channel surface wettability. Precise wettability patterning is difficult for devices containing multiple dropmakers, posing a significant challenge for parallelization. In this paper, we present a multilayer dropmaker geometry that greatly simplifies the process of producing microfluidic devices with excellent spatial control over channel wettability. Wettability patterning is achieved through the independent functionalization of channels in each layer prior to device assembly, rendering the dropmaker with a precise step between hydrophobic and hydrophilic channels. This device geometry enables uniform wettability patterning of parallelized dropmakers, providing a scalable approach for the production of double emulsions.
It remains a grand challenge to prepare anisotropic crystal superstructures with sensitive optical properties in polymer science and materials ﬁeld. This study demonstrates that semicrystalline polymers develop into anisotropic hollow spherulitic crystals spontaneously at interfaces of liquid drops. In contrast to conventional spherulites with centrosymmetric optics and grain boundaries, these anisotropic spherulitic crystals have vanished boundary defects, tunable aspect ratios, and noncentrosymmetric, orientationsensitive birefringence. The experimental ﬁnding is elaborated in poly(L-lactic acid) crystals and is further veriﬁed in a broad class of semicrystalline polymers, irrespective of molecular chirality, chemical constitution, or interfacial modiﬁcation. The facile methods and general mechanism revealed in this study shed light on developing new types of optical microdevices and synthesis of anisotropic semicrystalline particles from liquid emulsions.
Here, we demonstrate use of a Mg 2+ -dependent, site-specific DNA enzyme (DNAzyme) to cleave oligos from polyacrylamide gel beads, which is suitable for use in drop-based assays. , Here, we demonstrate use of a Mg 2+ -dependent, site-specific DNA enzyme (DNAzyme) to cleave oligos from polyacrylamide gel beads, which is suitable for use in drop-based assays. We show that cleavage efficiency is improved by use of a tandem-repeat cleavage site. We further demonstrate that DNAzyme-released oligos function as primers in reverse transcription of cell-released mRNA.