# State of the Art Review about Bio-Inspired Design and Applications: An Aerospace Perspective
## 4 Applications of Bio-Inspiration in the Aerospace Industry  
(a) Wing designs  
A design based on seagulls' capability to morph their wings to provide reasonable aerodynamic and flapping control was mimicked [62]. The gulls' variable wing action was implemented in an aircraft design using lightweight airframe components and an actuator. This control linkage-based system helped change the wing's morphology. Figure 15 depicts the morphing wing structure in an aircraft. The experimental and analytical analysis results were found to agree with each other, thus proving the bio-inspired concept. An implementation of a flapping wing mechanism attached rearwards to a fixed-wing in micro-air vehicles (MAVs) was studied in early 2005 [63]. Although the main, fixed element was found to provide most of the lift, the bio-inspired flappingwing provided more thrust and helped prevent flow separation for the main feature itself, thus improving the complete system's efficiency. A bird's wing's three-dimensional flapping motion was implemented in a MAV design using a four-bar mechanism [64]. The motive behind implementing such a plan was to replicate the spatial flapping of wings to provide a similar aerodynamic advantage. The  
Figure 15: Change in wing structure based on variable gull morphing capabilities [62]. spherical mechanism was used for flapping, which when compared with a non-spherical mechanism, provided a favorable flapping mechanism for flight applications. A humpback whale boasts a superior hydrodynamic performance by the tubercles on the leading edge of its flippers [64]. An inspired tubercle design on an aircraft's wing was developed to improve aerodynamic performance by increasing maximum lift and drag reduction. This could thus help reduce weight and fuel costs. Figure 16 depicts the implemented tubercle design on the wings and stabilizers of an aircraft. [PERSON]'s plane design and inspired bird wing design to mimic the swift and effortless wing action of birds that enabled flight was discussed [65]. The designs were based on the anatomy of birds, which made them capable of flight. A design inspired by a bird's wing's ability to change shape seamlessly, as indicated in Figure 17, depending on the flight itself was adopted to help provide enhanced performance [66]. A flexing parallelogram wing in place of a fixed, non-morphed wing element enabled an unmanned aerial vehicle (UAV) to reach its higher maximum velocity with a decrease in power requirement. The impact that the shape of an insect's flapping wing has on its aerodynamic performance was analyzed [67]. When comparing the profiles of wings with equal wingspans, the bumblebee and honeybee were noted to possess ideal wing shapes. In contrast, on comparing wing conditions with a similar wing surface, it was observed that the bumblebee  
Figure 16: Tubercles on the leading edge of the wings and stabilizers of an aircraft [64]. Figure 17: Design for a flexing parallelogram wing [66]. and the fruit fly had optimum wing shapes. Based on the shapes and other characteristics of an insect's wing, these data could be implemented successfully in larger aerodynamic applications to improve forward flight. An elastically deforming wing design was explored as flexibility and capability of the wing to deform play an essential role in improving the system's efficiency [68]. Figure 18 depicts the flapping-wing design. Wing deformations are commonly observed in insects such as dragonflies, locusts, and honeybees, with wing deformations being necessary to maintain lift. A similar synthetic, flexible wing design made of carbon fiber, Kapton, and Mylar films was analyzed. The analysis revealed that the artificial wing's elastic deformations matched closely with that of an insect, thus proving the concept of the design. A study for flight in the Martian atmosphere was numerically analysed [69].