261822 Controllable Microfluidic Production of Gas-in-Oil-in-Water Emulsions for Hollow Microspheres with Thin Polymer Shells

Monday, October 29, 2012
Hall B (Convention Center )
Jianhong Xu1, Ran Chen2, Pengfei Dong2, Yundong Wang3 and Guangsheng Luo2, (1)Department of Chemical Engineering, The State Key Lab of Chemical Engineering, Beijing, China, (2)Department of Chemical Engineering, The State Key Laboratory of Chemical Engineering, Beijing, China, (3)Department of Chemical Engineering, The State Key Laboratory of Chemical Engineering, Beijing, China

Controllable Microfluidic production of Gas-in-Oil-in-Water emulsions for hollow microspheres with thin polymer shells

Jian-Hong Xu,* Ran Chen, Peng-Fei Dong, Yun-Dong Wang, and Guang-Sheng Luo

(The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, China)

* Corresponding author. Tel.: +861062783870; Fax: +861062770304.

E-mail address: xujianhong@tsinghua.edu.cn

Encapsulation of microbubbles can be very useful. It helps eliminate the bubble dissolution and coarsening by separating the inner gas compartment from the outer fluid, ensuring the various potential applications of microbubbles in lightweight materials, aerated food products, waste water treatment3, ultrasound contrast agents and pharmaceuticals. Moreover, such a method can also be applied in the preparation of hollow particles, which are of great interest in areas such as energy-storage materials, catalyst supports and drug delivery carriers. Traditional ultrasonic approach provides an effective way in the encapsulation of the microbubbles, but it lacks control over the size and size distribution of the particles and the shell thickness. Here we introduce a simple and novel capillary microfluidic device by injecting a smaller capillary into another capillary and making sure that the tapered orifices align where the single-step emulsification carries on (Fig. 1). This simple microfluidic device ensures the flowing independency of the inner and middle phases and finally eliminates the defects. In this communication, we mainly introduce the application of such microfluidic device in the controllable fabrication of hollow microspheres with thin shells using G/L/L emulsion as templates.

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Fig.1 The sketch of the microfluidic capillary device and the microscope images of G/O/W droplets with different thickness of the oil layer, synthesized by tuning the flow rates of the middle phase.

We successfully produced Gas-in-Oil-in-Water double emulsions with high gas volume fraction using the simple and novel capillary microfluidic device. The size of the encapsulated microbubbles and the thickness of the oil layer can be easily controlled by adjusting the flow rates of oil and water phases. Such emulsions were used as the template for preparation of hollow core-shell microspheres with thin shells, as shown in Fig. 2.

Fig. 2 The LSCM and SEM photograph of the hollow microspheres after polymerization.

The hollow core-shell microspheres may find many applications in areas such as industrial catalysis, pharmaceuticals and delivery of cosmetics and nutrients. We believe that the approach we have demonstrated here is promising because it is suitable for the preparation of G/L/L emulsions with controllable structures, and it is a purely flow-controlled method, which is very simple to adjust the size and structure of G/L/L emulsions and hollow microspheres. Additionally, our approach is a one-step technology to realize microbubble encapsulation and hollow microspheres preparation. In the future work, we will try to explore the applications of the G/L/L emulsions in the area of the enhancement of Liquid/Liquid extraction, gas-liquid-liquid mass transfer and heterogeneous reactions.

Key words: G/L/L emulsion; microfluidic; hollow microsphere

Acknowledgement

The authors gratefully acknowledge the supports of the National Natural Science Foundation of China (21036002, 21136006), A Foundation for the Author of National Excellent Doctoral Dissertation of PR China (FANEDD 201053) and National Basic Research Program of China (2012CBA01203).


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