Structured thematic review of recent developments in 4D printing

Four-dimensional (4D) printing has emerged as a significant advancement in additive manufacturing by introducing time-dependent shape transformation and functional adaptation into printed structures. Through the integration of smart materials and external stimuli, 4D printing enables the development of responsive and self-transforming components for industrial, biomedical, and engineering applications. Despite the rapid growth of the field, recent developments remain dispersed across different research domains, making it challenging to obtain a comprehensive understanding of technological advances, manufacturing strategies, and emerging application frameworks. Therefore, a systematic review is necessary to consolidate the existing knowledge and identify the latest trends in modern 4D printing techniques for manufacturing. This study employed a Systematic Literature Review (SLR) approach in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Relevant literature was retrieved from the Web of Science and Scopus databases using the keywords “4D printing,” “additive manufacturing,” and “manufacturing.” Following identification, screening, eligibility assessment, and quality appraisal, 20 primary studies were selected for detailed analysis and synthesis. The findings revealed three major research themes. The first theme, Advanced Smart Materials and Functional Composites for 4D Printing, comprised 10 studies (50%) and highlighted developments in shape memory polymers, smart composites, self-healing materials, and multifunctional nanocomposites. The second theme, Process Design, Manufacturing Parameters, and Performance Optimization, comprised 5 studies (25%) and focused on printing parameters, residual stress control, shape recovery behavior, and manufacturing process optimization. The third theme, Applications, Intelligent Systems, and Emerging 4D Printing Frameworks, included 5 studies (25%) and covered biomedical applications, intelligent actuation systems, artificial intelligence integration, and emerging design frameworks for smart manufacturing. Overall, the reviewed literature indicates a transition from material-focused investigations toward integrated intelligent manufacturing systems that combine advanced materials, optimized processing strategies, and adaptive functionalities. Although substantial progress has been made, challenges related to scalability, material durability, process standardization, and industrial implementation remain. Future research should focus on developing robust smart materials, improving manufacturing efficiency, and strengthening the integration of artificial intelligence to facilitate the broader adoption of 4D printing in advanced manufacturing environments.