# Smart Infrastructure and Additive Manufacturing: Synergies, Advantages, and Limitations
## 6 Future Perspectives and Research Directions
### Emerging Trends in Self-Sustaining, Autonomous 3D-Printed Systems  
The development of self-sustaining, autonomous 3D-printed systems is a rapidly evolving field that holds significant promise for the future of smart cities. These systems integrate advanced technologies such as AI, ML, IoT, and renewable energy sources to create structures and devices that can operate independently with minimal human intervention [224]. By incorporating automation, real-time data processing, and self-repair mechanisms, these systems contribute to sustainable urban development while reducing long-term maintenance costs and resource consumption. This section explores some of the emerging trends in this area.  
A key trend in this field is the integration of renewable energy sources into 3D-printed structures. AI-driven design optimization enables the incorporation of photovoltaic materials, wind energy harvesting, and thermal insulation coatings, allowing structures to generate and store their own energy. This not only reduces the reliance on external power sources but also contributes to the sustainability goals of smart cities [225].  
Another trend is the use of smart materials that can adapt to environmental changes. These materials alter their properties in response to stimuli such as temperature, humidity, or mechanical stress, enabling the creation of adaptive structures that optimize their performance based on real-time conditions. For example, thermochromic windows can change their transparency to regulate indoor temperatures, reducing the need for artificial heating and cooling [226].  
The integration of IoT and AI technologies is further driving the evolution of autonomous 3D-printed systems. IoT sensors embedded in printed structures collect data on structural health, energy consumption, and environmental conditions, which AI algorithms analyze to optimize performance and maintenance [227]. Predictive maintenance enabled by AI reduces downtime and lowers operational costs, ensuring infrastructure reliability in rapidly changing urban environments. Additionally, AI-powered Digital Twins (DTs) serve as virtual models of physical structures, continuously analyzing real-time data to improve predictive maintenance and resource allocation.  
Soft robotics is another area where significant advancements are being made. Three-dimensional-printed soft robots are designed for applications such as infrastructure maintenance, environmental monitoring, and disaster response [228]. Their flexibility and adaptability allow them to navigate complex environments and perform tasks that traditional rigid robots cannot. Similarly, Wire-Arc Additive Manufacturing (WAAM) is emerging as a method for constructing large-scale, self-sustaining structures. WAAM builds components layer by layer using an electric arc to melt wire material, producing highly durable and complex structures ideal for urban environments [229].  
In conclusion, the emerging trends in self-sustaining, autonomous 3D-printed systems are transforming the conceptualization and development of urban infrastructure within smart cities. By integrating renewable energy sources, smart materials, IoT, AI, and advanced manufacturing techniques, these systems offer a sustainable and efficient solution for the challenges faced by modern cities. As these technologies continue to evolve, their potential to create more resilient, adaptive, and self-sustaining urban environments will only increase.