# State of the Art Review about Bio-Inspired Design and Applications: An Aerospace Perspective
## 3 Review on Manufacturing Methods Used in Bio-Inspired Design  
Greek architecture is the key inspiration for the earliest bio-inspired manufacturing methods Historically, accounts were seen in the Bolle di saponetraArte e Mathematica that described the geometry of a soap bubble. On a theoretical basis, it expanded from mathematics to architecture [1; 2; 3; 4]. The distinction was made after identifying characteristics and noting the earliest ones being drawn from mathematics. [PERSON] described the energy distribution, and it was the onset for manufacturing bio-inspired design. The conventional manufacturing techniques lay the early onset for minimal surface production. [1; 2; 3; 4]. The Topology optimization (TO) method was used across various industries, which followed the density-based approach. It used the DFAM aspect which resulted in more specific solutions to print bio-inspired structures which have a complex geometry [13]. [PERSON] et al. focussed on the adhesive-bonded specimens in a thermal cycle using 3D printing techniques [34]. The main advantage of AM techniques was the out-of-the-plane compressive response of panels, with bio fabrication. The inability of conventional manufacturing methods to produce complex geometries, limited applications, waste-production, and limited design structures led to the adoption a new manufacturing method [35]. Due to the complexity in nature, post-processing techniques were applied after powder-based processes [35]. The utilization of the selective laser sintering (SLS) method and its combination with six-design methods were used [36]. [PERSON] et al.broadly classified the different manufacturing processes of structures as depicted in Figure 7[37]. This highlighted a hierarchical approach to manufacture bio-inspired structures, with eventual growth from the organism level to the ecosystem level. Furthermore, the material structures were converted into the mason-slurry composition, which, incorporated by carbon nano tubes (CNT), amplified the reinforcing effects. The material layers and the hierarchical structure were proven successful in various applications, especially in aerospace [38]. These paved the way for the bio-inspired composites, which provide a near-net-shape for bio-inspired materials, which displayed anisotropic properties. It provided integration between AM and the techniques [39]. With the incorporation of 4D printing, there was an onset of shape memory transformations. In addition to 3D printed materials, it responded to environmental stimuli such as pressure, temperature, etc. [33]. The main advantage of AM was the key focus on sustainable development and production of high impact complex parts with material reduction. Product life cycle management was used for an all-encompassing bio-inspired method, from the physical characteristics to the design method. DFAM, sustainability, and bio-inspired design encompass the bio-inspired product [40]. SLS with a nylon powder and adhesive bonding was the technique used for this application. [PERSON] et al. gave a detailed explanation and the characteristics of each AM technique, as shown in Figure 8[28]. The structural-material properties were enhanced by the AM techniques, which were optimized for bio-inspired design, using generative design, topology optimization, and lattice structure design, as shown in Figure 9.