HKU Shenzhen Institute of Research and Innovation HKU SIRI

Shenzhen, China

HKU Shenzhen Institute of Research and Innovation HKU SIRI

Shenzhen, China
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Loo B.P.Y.,University of Hong Kong | Loo B.P.Y.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | Wang B.,University of Hong Kong
Telecommunications Policy | Year: 2017

In this paper, a holistic analytical framework for tracing and understanding the progress of e-development is developed and adopted in an empirical case study of China's e-development since 1998. In particular, the progress is analyzed systematically by benchmarking various ICT infrastructure and e-devices, the composition of Internet users, and the key dimensions of e-government, e-working, e-commerce, and e-networking. In addition, the questions of whether the geographical digital divide in the country has been narrowed is examined. Our findings show that (1) China has made noticeable progress in the e-development since 1998; yet, progress varied in different dimensions; (2) based on the overall performance, 2004 can be considered as the watershed for China to move from the formative stage to the developmental stage; (3) during the e-development, digital disparities in China have dramatically decreased at the provincial level, however, the urban-rural digital gap widened. We suggest that other than promoting affordable ICT possession, the wider and more diversified e-applications for different walks of life will be important for China to move towards the mature stage. © 2017 Elsevier Ltd.

Zhang L.,Tsinghua University | Hao S.,Tsinghua University | Liu B.,Tsinghua University | Shum H.C.,University of Hong Kong | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2013

We demonstrate an approach to prepare zirconium dioxide (ZrO2) microspheres by carrying out a diffusion-induced sol-gel reaction inside double emulsion droplets. A glass capillary microfluidic device is introduced to generate monodisperse water-in-oil-in-water (W/O/W) double emulsions with a zirconium precursor as the inner phase. By adding ammonia to the continuous aqueous phase, the zirconium precursor solution is triggered to gel inside the emulsions. The double emulsion structure enhances the uniformity in the rate of the sol-gel reaction, resulting in sol-gel microspheres with improved size uniformity and sphericity. ZrO2 ceramic microspheres are formed following subsequent drying and sintering steps. Our approach, which combines double-emulsion-templating and sol-gel synthesis, has great potential for fabricating versatile ceramic microspheres for applications under high temperature and pressure. © 2013 American Chemical Society.

Song Y.,University of Hong Kong | Song Y.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | Sauret A.,Princeton University | Shum H.C.,University of Hong Kong | Shum H.C.,HKU Shenzhen Institute of Research and Innovation HKU SIRI
Biomicrofluidics | Year: 2013

Immiscible aqueous phases, formed by dissolving incompatible solutes in water, have been used in green chemical synthesis, molecular extraction and mimicking of cellular cytoplasm. Recently, a microfluidic approach has been introduced to generate all-aqueous emulsions and jets based on these immiscible aqueous phases; due to their biocompatibility, these all-aqueous structures have shown great promises as templates for fabricating biomaterials. The physico-chemical nature of interfaces between two immiscible aqueous phases leads to unique interfacial properties, such as an ultra-low interfacial tension. Strategies to manipulate components and direct their assembly at these interfaces needs to be explored. In this paper, we review progress on the topic over the past few years, with a focus on the fabrication and stabilization of all-aqueous structures in a multiphase microfluidic platform. We also discuss future efforts needed from the perspectives of fluidic physics, materials engineering, and biology for fulfilling potential applications ranging from materials fabrication to biomedical engineering. © 2013 AIP Publishing LLC.

Li Z.,University of Hong Kong | Mak S.Y.,University of Hong Kong | Sauret A.,Princeton University | Shum H.C.,University of Hong Kong | Shum H.C.,HKU Shenzhen Institute of Research and Innovation HKU SIRI
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

We report a new method to display the minute fluctuations induced by syringe pumps on microfluidic flows by using a liquid-liquid system with an ultralow interfacial tension. We demonstrate that the stepper motor inside the pump is a source of fluctuations in microfluidic flows by comparing the frequencies of the ripples observed at the interface to that of the pulsation of the stepper motor. We also quantify the fluctuations induced at different flow rates, using syringes of different diameters, and using different syringe pumps with different advancing distances per step. Our work provides a way to predict the frequency of the fluctuation that the driving syringe pump induces on a microfluidic system and suggests that syringe pumps can be a source of fluctuations in microfluidic flows, thus contributing to the polydispersity of the resulting droplets. © 2014 The Royal Society of Chemistry.

Song Y.,University of Hong Kong | Song Y.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | Liu Z.,University of Hong Kong | Liu Z.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | And 4 more authors.
Chemical Communications | Year: 2013

We demonstrate the manipulation of viscous all-aqueous jets by electrical charging. At sufficiently high voltages, the folding of an uncharged viscous jet is suppressed, and the jet diameter can be adjusted by varying the applied voltage or the fluid flow rates. This inspires new ways to fabricate biocompatible fibers. This journal is © The Royal Society of Chemistry 2013.

Liu Z.,University of Hong Kong | Liu Z.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | Wyss H.M.,TU Eindhoven | Fernandez-Nieves A.,Georgia Institute of Technology | And 2 more authors.
Physics of Fluids | Year: 2015

We study the dynamics of two pinned droplets under the influence of an applied electric stress. We find that at a sufficiently strong field, this stress is sufficient to induce contact of the droplets. Interestingly, upon such contact, the dynamic behavior sensitively depends on the separation distance between the droplets. Besides the classical "coalescence" regime, we identify two other dynamic regimes: "fuse-and-split" and "periodic non-coalescence." In the "fuse-and-split" regime, the droplets first fuse to form a jet, which subsequently breaks up into two droplets. In the "periodic non-coalescence" regime, the droplets contact and bounce away periodically without coalescence. Further analysis indicates that while the electric stress stretches the droplets into shapes that depend on the initial droplet separation, the surface tension stress dominates over the electric stress as soon as the droplets touch.We show that the shapes of the contacting droplets determine their subsequent dynamics. Our work provides a rationale for understanding the interplay between surface tension and electric stresses that govern the behavior of charged droplets and could inspire new methods for characterizing emulsion stability and surfactant performance. ©2015 AIP Publishing LLC.

Liu Z.,University of Hong Kong | Liu Z.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | Shum H.C.,University of Hong Kong | Shum H.C.,HKU Shenzhen Institute of Research and Innovation HKU SIRI
Biomicrofluidics | Year: 2013

In this work, we demonstrate a robust and reliable approach to fabricate multi-compartment particles for cell co-culture studies. By taking advantage of the laminar flow within our microfluidic nozzle, multiple parallel streams of liquids flow towards the nozzle without significant mixing. Afterwards, the multiple parallel streams merge into a single stream, which is sprayed into air, forming monodisperse droplets under an electric field with a high field strength. The resultant multi-compartment droplets are subsequently cross-linked in a calcium chloride solution to form calcium alginate micro-particles with multiple compartments. Each compartment of the particles can be used for encapsulating different types of cells or biological cell factors. These hydrogel particles with cross-linked alginate chains show similarity in the physical and mechanical environment as the extracellular matrix of biological cells. Thus, the multi-compartment particles provide a promising platform for cell studies and co-culture of different cells. In our study, cells are encapsulated in the multi-compartment particles and the viability of cells is quantified using a fluorescence microscope after the cells are stained for a live/dead assay. The high cell viability after encapsulation indicates the cytocompatibility and feasibility of our technique. Our multi-compartment particles have great potential as a platform for studying cell-cell interactions as well as interactions of cells with extracellular factors. © 2013 AIP Publishing LLC.

Shimanovich U.,University of Cambridge | Song Y.,University of Hong Kong | Song Y.,HKU Shenzhen Institute of Research and Innovation HKU SIRI | Brujic J.,New York University | And 3 more authors.
Macromolecular Bioscience | Year: 2015

Peptides and proteins represent attractive building blocks for the development of new functional materials due to the biocompatibility and biodegradability of many naturally abundant proteins. In nature, sophisticated material functionality is commonly achieved through spatial control of protein localisation and structure on both the nano and micro scales. We approached this requirement in an artificial setting by exploiting the propensity of proteins to self-assemble into amyloid fibrils to achieve nano scale order, and utilised aqueous liquid/liquid phase separation to control the micron scale localization of the proteinaceous component under microconfinement. We show that in combination with droplet microfluidics, this strategy allows the synthesis of core-shell microgel particles composed of protein nanofibrils. It shown that the characteristics of aqueous two-phase systems can be exploited in combination with protein self-assembly for controlling aggregation and structuring of fibrillar proteins into 3D core-shell microgels. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chan Y.K.,University of Hong Kong | Wong D.,University of Hong Kong | Yeung H.K.,University of Hong Kong | Man P.K.,University of Hong Kong | And 2 more authors.
Investigative Ophthalmology and Visual Science | Year: 2015

PURPOSE. Silicone oil (SO) has been used as a long-term intraocular tamponade in treating retinal diseases for more than half a decade. However, its propensity to form tiny SO droplets is associated with a number of complications. Currently there is no effective way to remove such droplets from the eye cavity. In this work, a novel cleaner was developed for effective removal of these droplets. METHODS. The cleaner promotes the formation of an oil-in-water-in-oil (O/W/O) doubleemulsion that consists of the unwanted droplets as the innermost oil phase. The cleaner’s ability to encapsulate SO droplets was tested using both in vitro microdevices and ex vivo porcine eye models. The efficiency of the cleaner in removing the SO droplets was quantified using the three-dimensional (3D) printed eye model. Both the volatility and in vitro cytotoxicity of the cleaner were evaluated on three retinal cell lines. RESULTS. Cleaner 1.0 is volatile and has an evaporation rate of 0.14 mL/h at room temperature. The formation of O/W/O double-emulsion indicates the encapsulation of SO droplets by the cleaner. In the 3D printed eye model, rinsing with cleaner 1.0 led to a significant reduction of leftover SO droplets compared with 13 phosphate-buffered saline (PBS; P < 0.05; n ¼ 6). Cleaner 1.0 did not cause significant cell death (3%–6%) compared with balance salt solution (BSS; 1%–3%) in all three cell lines. The reduction in the cell viability due to cleaner 1.0, relative to that of BSS, was significant only in ARPE-19 cells (27%; P < 0.05) but not in the other two cell lines (8% and 17%, respectively; P > 0.05). CONCLUSIONS. The double-emulsification approach was effective in removing remnant droplets from the eye cavities, and the cleaner was compatible with common cell types encountered in human eyes. The mechanism of toxicity of the proposed cleaner is still unknown, therefore, further in vivo animal tests are needed for full evaluation of the physiological response before the proposed cleaner can be advanced to clinical trials for retinal surgeries. © 2015 The Association for Research in Vision and Ophthalmology, Inc.

Kong T.,University of Hong Kong | Kong T.,HKU Zhejiang Institute of Research and Innovation HKU ZIRI | Wang L.,University of Hong Kong | Wang L.,HKU Zhejiang Institute of Research and Innovation HKU ZIRI | And 3 more authors.
Soft Matter | Year: 2014

In this work, we have developed a facile, economical microfluidic approach as well as a simple model description to measure and predict the mechanical properties of composite core-shell microparticles made from materials with dramatically different elastic properties. By forcing the particles through a tapered capillary and analyzing their deformation, the shear and compressive moduli can be measured in one single experiment. We have also formulated theoretical models that accurately capture the moduli of the microparticles in both the elastic and the non-linear deformation regimes. Our results show how the moduli of these core-shell structures depend on the material composition of the core-shell microparticles, as well as on their microstructures. The proposed technique and the understanding enabled by it also provide valuable insights into the mechanical behavior of analogous biomaterials, such as liposomes and cells. © 2014 the Partner Organisations.

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