PTV-Based Measurement of a Local Flow Field in a Microfluidic Dragonfly Forewing Model

Wings are critical for insects, and blood flowing through wing veins is crucial for maintaining the function and integrity of insect wings. Insect wing circulation has been investigated by observing the motion of blood cells or injected microspheres through the veins of live insects. However, using live insects is limited in studying detailed local patterns of blood flow. To overcome the limitation, we developed a microfluidic replica of the forewing of a dragonfly (Common Green Darner; Anax junius) using a high-resolution picture of the wing, photolithography, and PDMS (polydimethylsiloxane)-based soft lithography. Phosphate buffered saline (PBS) with 20 μm-diameter polystyrene beads was steadily injected into the device. The movement of the beads in a region of interest with complicated vein geometries was imaged by high-speed video microscopy. Recorded images were processed using MALTAB-based particle tracking velocimetry (PTV) code to determine the local flow field. Our processed PTV result shows that overall flow direction was from the leading edge vein to the trailing edge vein of the wing, and from the wing base toward the wing tip. The flow directions in the region of interest were comparable to previous studies on blood circulation in dragonfly wing veins. This agreement supports our idea that microfluidic insect wing vein models can recreate the blood flow of corresponding wings in vitro and enable detailed investigation of the local flow field.