# New Trends in 4D Printing: A Critical Review
## 8 Future Position in Industry  
In the age of Industry 4.0, 4 DP has the potential to give the manufacturing industry a significant competitive advantage by reducing the required assembly parts and resources. Because of their biocompatibility and qualities comparable to natural materials, SMMs offer considerable promise in biomedical applications, biosensors, drug delivery systems, and tissue regeneration. The development of novel materials such as non-invasive biomedical devices is extensive, and procedures depend critically on the analysis and simulation of natural phenomena. New composite SMs are an intriguing solution in tissue engineering applications. In addition, printable materials for tissue repair and regeneration must have sufficient printability, mechanical strength, interfacial strength, and biocompatibility. However, obtaining suitable printable biomaterials remains difficult. As a result, it is critical to create novel printable biomaterials for 4 DP constructions in tissue repair and regeneration.  
In addition, this technique offers enormous promise for overcoming the numerous inherent flaws of functional components. Although 4 DP as a technology is relatively new and requires time and effort for its adoption, it has the potential to provide possibilities for many sectors. Innovative 4 DP processes can reduce the number of components and consequently the assembly time. Following the polymer revolution, SM and AM technologies are predicted to drastically cut fuel consumption and emissions in the aircraft sector.  
The use of advanced composite materials for 4D structures has received more attention, as researchers have developed structures that respond to stimuli by producing differentialstrains. Printing SMs or smart voxels leads relevant study areas and scientific communities to new multidisciplinary and convergent research paradigms. Various research initiatives on increased SMAs and SMPs are documented in the literature; however, certain issues require further research. 4 DP as a multi-material structure allows for more flexibility in shape shifting by printing passive and active bilayers. Furthermore, SMs are tailored on a laboratory scale in various research projects by merging two or three SMMs using particular form changes.  
Scientists and engineers are focusing on the improvement of multi-material design for specific applications; however, understanding of the technology should consider various factors. The 4 DP process factors and parameters impacting SMs should be thoroughly examined, as should their interrelationships, particularly as a function of time.  
Digital materials might be used for smaller interconnecting parts, which may help in the transport and assembly of large components. Materials may be turned into simple, repetitive, useful pieces rather than large, monolithic, single-use components. The expanding materials could be carefully positioned on the main structure to make joints that stretch and fold when triggered by water, generating a wide diversity of forms. The process is designed to yield larger structures that can handle more complicated transformations in the future, as well as smaller, miniaturized ones that can be employed in an aircraft's fuselage. Electroactive polymers, pressurized fluids or gases, chemical stimuli, and even light have all been successful in changing form.  
4 DP can be used in the logistics sector to reduce production and transportation costs, improving the global supply chain system. In addition to self-assembly and self-expansion abilities, self-repair is a key element. On the other hand, 4 DP might be the next generation of lean manufacturing [193]. Further advancements can be provided by 5D printing [194,195] and 6D printing [196,197]. In particular, the combination of both the print head and the component allows for reducing the fabrication time of curved surfaces without supports [197].