## 6 Current Challenges and Future Prospects
### Present Obstacles Faced by AM Technologies
#### 6.2.1 Bioprinting  
Bioprinting merges 3D printing with biology to craft living tissue and organs using bioink [109; 110]. This process, made possible by specialized bioprinters, has enormous ramifications for drug testing [111], tissue engineering [112] and organ transplantation [113], changing regenerative medicine and healthcare. With precise cell and material placement [114], bioprinting holds potential for personalized medicine [115], better patient outcomes [116], and innovative therapies [117], driving scientific research forward. Bioprinting is held back by several issues that prevent it from becoming widely used. These include maintaining the health and usefulness of printed tissues [118], the limited supply and complicated nature of the necessary biomaterials [119], the need to produce larger quantities, and ethical concerns that need to be addressed. Overcoming these obstacles is essential to unlock bioprinting's full potential in healthcare and regenerative medicine [120]. Despite all of this, the future of bioprinting is bright, poised to transform healthcare and regenerative medicine. Progress in this field could result in organs, tissues, and implants tailored to individual patients, potentially shortening the wait for transplants and enhancing patient recovery and results [121]. bioprinting also enhances drug testing and personalized medicine through realistic organ models. Continued progress in biomaterials and techniques could enable printing of complex structures like blood vessels, addressing organ shortages and revolutionizing regenerative medicine [122; 123; 124]. Currently, there is increasing enthusiasm for developing highly durable, eco-friendly, biodegradable, and easily manufacturable products using various AM technologies. It is crucial to understand the environmental regulations associated with the utilization of bioprinting technologies for each manufacturing process [46; 125; 126]. This segment explores advanced additive manufacturing techniques known as 4D and 5D printing. 4D printing incorporates the dimension of time, enabling objects to transform and develop over time, while 5D printing combines complex movements and both additive and subtractive processes. These technologies create objects and materials that can change their form, traits, or capabilities in response to environmental changes [127; 128]. By using intelligent materials and innovative designs, 4D/5D printing opens new opportunities in aerospace, healthcare, robotics, and consumer products. These advancements could revolutionize manufacturing with self-building structures, adaptable gadgets, programmable textiles, and smart systems, marking a new era of innovation [46]. Despite the promise of 4D/5D printing, several challenges must be addressed for widespread adoption. Key issues include developing and integrating smart materials that respond predictably to stimuli while maintaining structural integrity, as well as ensuring their availability and scalability [129]. Improvements are needed in design, manufacturing processes, and materials understanding to precisely manage shape changes [130]. Additionally, resolving complexity and cost issues is essential to enhance accessibility and affordability. Standardization and regulatory considerations are critical for ensuring safety, reliability, and compatibility across industries. In order to fully utilize 4D/5D printing as a revolutionary manufacturing technique, certain obstacles must be overcome [46; 131; 132; 133]. The prospects of 4D/5D printing technologies are poised to revolutionize various industries and enable innovative applications. These developments may lead to the creation of complex things with environmental adaptability and customization capabilities [135]. Intelligent implants in healthcare might improve patient outcomes by adjusting to physiological changes. Shape-shifting structures in aircraft might improve fuel economy.