Study On Microflow In An Alveolus Using A Microfluidic Chip

Lung is the respiratory organ of the human body.Its internal environment is directly connected to the external environment.Long-term exposure to particulate contaminants and toxic aerosols leads to chronic obstructive pulmonary disease(COPD),asthma and other diseases.However,there is a lack of understanding in the transport and deposition of micro-nanoparticles within the deep lung,which are mainly determined by the flow in the alveolus.Therefore,understanding the complex flow fields in alveoli is of great significance for studying the transport and deposition of fine particles in the deep lung.However,the existing experimental studies in vitro cannot fully realize the dynamical similarity of the flow between the experimental model and the alveoli of different generations,so the understanding of the flow field in the alveoli at all levels is not enough.In this paper,based on the precise dynamic matching,the microfluidic experiments were carried out in a microfluidic alveolar chip.The flow fields of different alveolar generations were reconstructed in a chip,and the stagnation saddle points were observed in the flow field.Before the experiments,the characteristic sizes and main respiratory parameters of alveoli and alveolar ducts were collected and calculated.Based on the Anatomical structure and size,a quasi-three-dimensional alveoli chip was designed and fabricated.The alveolar wall expands and contracts periodically,and the fluid in the alveolar duct oscillates cyclically at the same time to mimic respiratory movement.The different flow patterns in alveoli were reproduced by controlling the dynamical similarity of the flows in the chip and the real alveoli of different generations.In addition,the experiments also observed stagnation saddle points,which were the sign of chaotic flow.The occurrence rules of saddle points were analyzed.This is the first time to prove the existence of complex chaotic flow in alveoli through in vitro experiments preliminary.It was also found that the height of the quasi three-dimensional chip had a significant effect on the flow field in the alveoli.Therefore,the numerical simulation method was used to study the flow field in different height models.Different flow patterns were obtained,and the influence of model height on the flow patterns was analyzed and summarized.The stagnation saddle points were also found in the simulation flow field under the condition of fixed wall.The conditions of occurrence of saddle points are derived.In this paper,the flow fields and velocity distributions in the quasi-three-dimensional model of different heights are compared to that in the three-dimensional model.The suitable height range of the quasi-three-dimensional model to mimic 3D models was summarized.The simulation experiment proved the rationality of the above-mentioned microfluidic alveolar chip.It also provided data reference for the future design of the quasi-three-dimensional model.