Microcapsules are widely found in the nature (e.g. red blood cells and some bacteria), as well as in artificial products. They are generally well-considered as liquid drop bounded by an elastic membrane which is often used to protect the core materials from the external harsh environments. Capsules of biopolymers are exhibiting a large increase of promising applications in the encapsulation and release of medical drugs, food additives, and cosmetics[1-3]. Indeed, there is also a growing interest to model the dynamics of red blood cells (RBCs) motion in vessels or circulations using artificial microcapsules. Particularly, in some cases, it requires the homogeneous physic-chemical properties of capsules, such as uniform size, same shell structure and mechanical characteristics. Therefore, the most challenging work could be to develop a facile strategy to synthesis microcapsules with controlled properties-determined parameters.

The preparation of monodisperse microcapsules involves emulsification of the disperse phase into the continuous phase which both are immiscible. There are several strategies been developed to fabricate capsules including batch methods (high-pressure valve homogenisers, static mixers, and rotor stator systems), electrospray techniques, and emulsification through membrane pores. These methods, however, require multistage emulsion processes, and capsules obtained with non-uniform properties and a largely wide distribution of sizes[4-5]. To overcome these problems, recently, microfluidic controlling techniques are introduced, by which monodisperse biopolymer capsules in micrometer size ranges are allowed to be generated in a single step.

The main purpose of this study is to develop an approach of fabricating monodisperse biopolymer microcapsules with homogeneous properties on the base of microfluidic controlling components. Thereafter, the membrane properties of obtained capsules are proposed to be measured consisting of flowing a capsule suspension into an elongation flow. The deformation of capsules in the elongation flow can be divided into two regions: linear and non-linear zones. Surface shear elastic modulus of the shell in the linear region (small deformation) and membrane wrinkles instability or plastic deformation in the non-linear region are detected, respectively. Furthermore, thanks to the microfluidic techniques, the interfacial rheological properties of microcapsules are able to be modified via the synthetic procedures, such as the concentrations of chemicals and interfacial polymerization time. Results show that the physic-chemical properties of biopolymer capsules produced by the microfluidic route are very close for the same generating lot.