Circulatory flow patterns in a dragonfly wing elucidated from a microfluidic model

Insect wings consist of a network of tubular veins and thin inter-connected membrane. Within these veins are hemolymph (blood), tracheal branches (oxygen delivery), and nerves connected to vital sensory organs on the wing. Since blood flow supplies water and nutrients to the sensory organs and other tissues and removes waste products, veins and hemolymph flow are crucial for stability, flexibility, and functionality of the delicate wing blade. However, the relationship of wing venation on hemolymph circulation remains poorly studied. Previous experiments tracking hemocytes (blood cells) in transparent veins of living specimen gave some insight into some flow patterns. To investigate detailed hemodynamics in complex wing venation, we used photo/soft-lithography to create a microfluidic wing vein model of the dragonfly, Anax junius. Blood flow was simulated by injecting dyed water into the veins using a range of flow velocities and input locations. Microbeads were used to characterize local flow patterns within the veins. Visualized flow patterns suggested that advection dominates near the wing base, whereas diffusion dominates toward the wing tip. Biomimetic wing vein devices allow for further investigation into the insect wing’s unique circulatory system and transport phenomena.