From grasshoppers to gliders: evaluating the role of hindwing morphology in gliding flight

Grasshoppers seamlessly alternate between flapping and gliding, adapting to changing conditions and conserving energy. This study examines the hindwings of the Schistocerca americana grasshoppers and determines the key elements of the wing features that can enable insect-scale flyers to use gliding as a mode of flight. Wing-specific elements include planform shape, camber profile and corrugation patterns. The study begins with a morphological study of S. americana hindwings and characterizes their aerodynamics through water channel experiments of grasshopper-inspired wing models. We then design, fabricate and evaluate, through flight testing, a grasshopper-inspired glider. Results reveal that while a corrugated wing model has the highest aerodynamic efficiency at low angles of attack, its aerodynamic efficiency decreases at higher angles of attack. In contrast, the glider with the wing model that captures the wing planform shape and has a simplified camber profile exhibits consistent aerodynamic efficiency across a wide range of angles of attack and repeatable flight performance. Therefore, we have identified that the wing planform and a simplified camber profile are key parameters when designing insect-scale gliding robots. The results lay the groundwork for advancing insect-scale robots that exploit gliding flight, offering new opportunities for untethered locomotion with low energy expenditure.