# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 5 Shape Change Manipulation Using Laser Processing  
Creating smart materials using laser processing and shape change manipulation is a modern approach that involves using laser irradiation to induce controlled changes in the shape and dimensions of a material. It is particularly useful for developing materials with shape memory properties, making it suitable for 4D processes, such as the creation of objects that can change their shape in response to various cues [135; 136; 137]. 4D printing is an emerging technology that extends the concept of 3D printing by adding an additional dimension--time. In 4D printing, the printed object is designed to change its shape  
Figure 10: (**a**) Experimental setup features a compact DLIP optical configuration, with the main beam divided into four identical sub-beams using a DOE. Inset displays four symmetrically distributed sub-beams with \(\theta\) as the incidence angle and \(\phi\) as the azimuthal angle. Interference intensity patterns are illustrated for two setup variants: (**b**) without and (**c**) with a DOE [132]. or function over time when exposed to specific environmental conditions or external stimuli. The process typically involves printing a structure using materials with special properties, such as shape-memory polymers [138; 139; 140; 141] or composites with responsive elements [142; 143; 144; 145], ceramics are also finding applications [146; 147; 148]. These materials are programmed to react to external factors like heat, moisture, light, or magnetic fields. When the printed object is subjected to the predetermined stimulus, it undergoes a transformation, changing its shape, structure, or properties. The technology holds great promise, as it allows for the creation of objects that can adapt and optimize their performance in real time. The progress in high-temperature ceramics is hindered due to their extreme melting points and the challenge of crafting complex structures. 4D printing emerges as a solution, enhancing the geometrical flexibility of ceramics. In [146], a ceramic 4D printing method combining laser machining, UV/ozone film deposition, and heat treatment is presented. It induces rapid shape and material changes, allowing versatile structures with tunable bending. Precursors transform into ZrO\({}_{2}\)-SiOC ceramics or SiOC glass, showcasing reversible reconfigurability and shape memory. The 4D printing of metallic materials often employs specific metal alloys with shape memory properties. These alloys can include, but are not limited to the following. Nitinol (Ni-Ti) is a well-known shape memory alloy that consists of nickel and titanium. It is widely used in various applications due to its excellent shape memory and superelasticity properties [149; 150; 151]. Copper-based shape memory alloys, like Cu-Al-Mg and Cu-Zn-Al, can be utilized for 4D printing applications, offering good shape memory behavior and mechanical properties [152; 153]. Fe-Mn-Si alloys, containing iron, manganese, and silicon, have emerged as a promising option for 4D printing. Recent research highlights their potential, as exemplified by [154], which demonstrated the ability to tailor the microstructure of Fe-Mn-Si shape memory alloys via changes in laser powder bed fusion parameters. Samples were produced using laser powder bed fusion (LPBF) with a 200 W fiber laser machine equipped with a quartz F-Theta lens, resulting in a laser spot diameter of 55 \(\upmu\)m. The manufacturing process involved three different scanning velocities: 100 mm/s, 250 mm/s, and 400 mm/s. The laser power was consistently maintained at 175 W for all samples. Additionally, a uniform distance between the centers of the applied tracks was chosen as 100 \(\upmu\)m. In [155], the impact of heat treatment and thermomechanical training on both conventional and additively manufactured FeMnSi-based shape memory alloys was studied.