# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 5 Shape Change Manipulation Using Laser Processing
Additive manufacturing samples were produced using a LPBF machine equipped with a 1070 nm fiber laser and a spot size of 55 \(\upmu\)m. The scanning strategy employed a bidirectional approach without border contour, followed by a 90\({}^{\circ}\) rotation between layers. The optimized parameters consisted of a scanning speed of 225 mm/s, a laser power of 175 W, a layer thickness of 0.03 mm, and a hatch spacing of 0.1 mm. Heat-treated, additively manufactured samples exhibited the highest total recovery strain due to smaller grain size and a higher volume fraction of precipitates. In [156], the study investigated the influence of laser energy density on the properties of Fe-Mn-Si-Cr-Ni shape memory alloys during the fabrication process, thus offering insights for optimizing intelligent structures. Fe-Mn-Si-Cr-Ni samples were produced on a 316 stainless steel substrate using the LPBF machine equipped with a 400 W Ytterbium fiber laser. The hatch spacing and layer thickness were maintained at 0.08 mm and 0.03 mm, respectively. Throughout the fabrication process, volumetric energy densities were adjusted in the range of 42 to 300 J/mm\({}^{3}\) by varying both the laser power (ranging from 100 to 360 W) and the scanning speed (ranging from 500 to 1000 mm/s). The study in [157] introduces an innovative category of buckling-induced architected Fe-SMAs (BIA Fe-SMAs) composed of Fe-Mn-Si-Cr-Ni, fabricated by 4D printing. These alloys exhibit significant energy dissipation and shape recovery capabilities, thereby enhancing their multifunctionality. The production of samples was conducted using an LPBF machine equipped with a 1070 nm fiber laser featuring a Gaussian intensity distribution, a spot size of 55 \(\upmu\)m, and a maximum output power of 200 W. For experimental investigations,the laser power was set to 175 W, the layer thickness to 0.1 mm, and the hatch spacing to 0.03 mm. The applied scanning speed varied between 225 mm/s and 300 mm/s for different groups of samples. In Figure 11, diverse potential practical applications of 4D printed BIA Fe-SMAs are visually explored, showcasing their efficiency in absorbing and dissipating energy in a reusable context. Depending on the desired characteristics, other binary or ternary alloys may be used, such as nickel-titanium-hafnium (Ni-Ti-Hf) [158]. An LPBF machine was configured with an ytterbium fiber laser with a power of 300 W, operating at a wavelength of 1070 nm and featuring a spot size of 80 \(\upmu\)m. The input parameters for the fabrication of Ni-Ti-Hf using LPBF encompassed laser power settings of 135 W and 175 W, scanning speeds of 400 mm/s, 600 mm/s, and 950 mm/s, hatch spacings of 135 \(\upmu\)m and 140 \(\upmu\)m, along with the layer thickness. The advancement of 4D printing has primarily focused on thermal shape memory alloys. Nevertheless, with magnetic shape memory alloys, such as those of the Ni-Mn-Ga system, receiving attention [159]. The choice of alloy depends on the specific application and the desired behavior of the 4D-printed object. Different alloys may offer varying levels of shape memory properties, transformation temperatures, and mechanical characteristics, making it essential to select the most suitable material for the intended purpose. Applications of shape change manipulation using laser processing can be varied. Shape memory alloys and polymers with laser-induced shape change capabilities are used in minimally invasive medical devices, such as stents and catheters, which can be inserted in a compact form and then expanded to their functional shape within the body [160,161]. Shape memory materials that respond to laser heating are applied in aerospace components, such as aircraft wings and control surfaces, to enable adaptive aerodynamics [162]. Smart materials with shape memory properties are used in robotics to create self-deploying structures and adaptive robotic components [15]. Shape memory alloys can be integrated into consumer electronics, such as smartphones, to enable adaptable form factors or user interfaces [163].