# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 3 Harnessing Photothermal Reactions and Functional Additive Introduction  
Laser modification allows one to utilize the possibilities of photothermal reactions and encompasses the introduction of functional additives to transform material properties. The creation of smart materials through photothermal reaction energy allows for the controlled modification of material properties by using laser beams to manipulate their physical characteristics. Photothermal reactions involve the utilization of laser beams to heat materials, ultimately inducing changes in their structure and properties [41; 90]. The  
Figure 4: Differential interference contrast (DIC) microscopy images of wet-etched quartz surfaces, with an etch depth of 100 \(\mu\)m: (a) quartz surface after 4 h of etching without laser treatment before etching; (b) quartz surface after 4 h of wet etching under the same conditions as in (a) but after laser treatment before etching [77]. process begins by selecting a material capable of absorbing laser radiation, typically within a specific wavelength range [91]. The laser beam is precisely directed to the material's surface, where its energy is efficiently converted into thermal energy. The temperature increase achieved can be localized and extremely precise due to the focusing of the laser beam [92; 93]. Under the influence of laser irradiation, a photothermal reaction takes place, resulting in modifications to the material's internal structure and properties. These changes may encompass alterations to the crystalline structure, molecular orientation, or other physical parameters of the material. To achieve the desired material changes, it is crucial to control laser processing parameters, including laser beam power, duration of exposure, and the precise location of irradiation [94]. As a consequence of the photothermal reaction, the material can acquire \"smart\" properties, leading to changes in its optical, mechanical, or electrical characteristics, depending on the level or duration of laser exposure [95]. This capability enables the creation of materials with adaptive properties. Photothermal reactions play an important role in the production of materials that respond to specific therapeutic or diagnostic laser procedures [96; 97]. By initiating a photothermal reaction through laser irradiation, precise control and modification of material properties are achieved, making them \"smart\" and adaptable for a wide range of applications. The development of smart materials can also encompass the integration of specialized additives or compounds through laser processing. These functional additives have the capacity to introduce novel properties and functionalities to materials [98; 99]. For instance, in [100], a study aimed to enhance the bioactivity and wear resistance of titanium and its alloys for potential implant applications. This was achieved through laser cladding, resulting in a multilayer Ca/P (calcium/phosphorus) bio-ceramic coating on the surface of Ti6 Al4V alloy using hydroxyapatite and Ti powder as cladding precursors. The laser cladding system featured a medium-power fiber laser and a laser head connected through a QBH standard connector for efficient interchangeability. Laser cladding parameters included a 400 W laser power, 3 mm/s scanning speed, 2 mm spot diameter, and a 30% overlap rate. Figure 5 illustrates the laser cladding process employed to produce the multilayer Ca/P bio-ceramic coating. The resulting coating displayed good biocompatibility (Figure 4), similar to the commonly used Ti6 Al4V alloy for medical implants and showed in vitro bioactivity by facilitating hydroxyapatite deposition through ion exchange in an SBF solution, unlike the titanium alloy substrate. Additionally, the coating demonstrated enhanced wear resistance compared to the Ti alloy substrate. Using laser processing, various methods are available for the introduction of functional additives into materials.