Experiment And Numerical Simulation Of Microcapsules Prepared By One-Step Microfluidic Method

As an ideal carrier,microcapsules can encapsulate active substances effectively,and can realize intelligent response and controllable release of encapsulated substances under specific conditions.In the process of preparing microcapsules by traditional methods,double-emulsion template is generally obtained by high-speed shearing,whose microcapsules are prepared by further solidification.However,microcapsules prepared through these methods usually exhibits some problems of complicated operation,poor controllability and low efficiency of encapsulation.In recent years,with the development of microfluidic technology,microcapsules with uniform size,controllable shell thickness and high efficiency of encapsulation can be prepared.While preparation of microcapsules by microfluidic technology are still complicated,and highthroughput preparation of microcapsules is also difficult to achieve,which limits the wide application of microcapsules.Thus,a method to prepare microcapsules is proposed by combining microfluidic technology with gravity effect.Besides,by means of the design and optimization of parallel amplification microfluidic devices,high-throughput preparation of microcapsules can be realized.Main research contents are as follows:(1)A method for preparing microcapsules based on microfluidic one-step emulsification is proposed,which combines microfluidic technology with gravity effect.Dispersed phase and continuous phase are extruded from the inner and outer glass capillary orifices,respectively,by adopting a co-axial microfluidic device.The two-phase fluid is finally pulled away from the orifice of the glass capillary to form a double-emulsion droplet and finally falls off under the condition that inertial force and gravity overcome viscous force and interfacial tension.The sodium alginate in outer layer of the double-emulsion droplet and calcium chloride solution crosslink to form microcapsules,which encapsulates active substance by the cross-linked shell with certain mechanical strength to avoid affection by external environment.Compared with traditional methods,it only needs just one emulsification operation by this method,which improves the preparation efficiency,and exhibts excellent monodispersity and efficiency of encapsulation.(2)Combined experiments with numerical simulations,various parameters related to the microcapsules’ characteristics are systematically investgated in water-oil and water-water systems,respectively.First,the phase diagram of the microcapsules is obtained by changing the flow rate of dispered and continuous phases,whose microcapsules exhibit a single core structure and excellent monodispersity.Then,the effects of parameters such as the flow rates of dispersed and continuous phase,microfluidic device structure,interfacial tension between continuous phase and air,interfacial tension between dispersed and continuous phase,the viscosities of dispersed and continuous phase related to the characteristics of microcapsules are investigated detailedly.And each parameter is carefully analyzed in theoretical level.Finally,the microcapsules are put in an acidic or alkaline environment,respectively,in order to realize intelligent response and controllable release.Therefore,broaden the practical application of the microcapsules.(3)Based on the parallel amplification theory of microchannels,draw on the experience of the successful preparation of microcapsules by means of a single channel,a 10-channel microfluidic device is designed and manufactured by 3D printing technology,in order to realize the high-throughput preparation of microcapsules.First,according to the flow distribution law in the ladder network structure and the flow resistance calculation formula in the circular microchannel,size distribution relationship between the main channel and the branch channel is determined.Then,a 10-channel microfluidic device is designed and manufactured by photocuring3 D printing.Finally,water-core microcapsules are successfully prepared by the 10-channel microfluidic device.And it is found that the microcapsules prepared by each channel show good monodispersity and stability,keeping consistent with the microcapsules prepared by a single channel microfluidic device.During the continuous preparation for 4 hours,the diameter and shell thickness of the microcapsules do not fluctuate,proving that the high-throughput preparation of microcapsules can be realized through this method,which open an avenue for industrial production of microcapsules.