Microscopic dynamics research in the process of cell encapsulation with microfluidic chips

Cell encapsulation is of vital importance in biomedical applications, but mechanical damage during microfluidic processes compromises cell integrity and reduces encapsulation efficiency. This study constructs a dual layer spring network model, multiphase simulations, combined with experimental verification, to analyze transient microscale mechanics of L929 cells during injection and encapsulation in a microchannel. This work identifies two critical risk stages: (i) during injection, cells undergo varying degrees of compression and shear under different dispersed phase conditions; (ii) during encapsulation, cells at different neck positions are subjected to varying shear forces, leading to different encapsulation outcomes. Higher injection velocity increases cellular pressure. Both excessively high and low dispersed phase viscosities lead to elevated shear stress, whereas moderate viscosity and low injection velocity reduce shear and membrane strain, helping preserve cell integrity and enhancing encapsulation efficiency. During encapsulation, successful encapsulation largely depends on the position the cell reaches as it moves into the droplet neck. Rear neck cells face stronger shear and a higher risk of damage, while front neck cells are more easily encapsulated. Additionally, increasing the continuous phase velocity intensifies local pressure fluctuations, further raising the risk of membrane damage. Experimental results demonstrate that a flow rate ratio of 7–8 yields approximately 75% encapsulation efficiency, while ensuring stable and uniform droplet formation. This work quantifies how cell damage risk varies with encapsulation position, continuous phase velocity, and dispersed phase viscosity and flow rate. These findings offer guidance in optimizing mechanical conditions to improve cell viability and encapsulation performance.