Volumetric additive manufacturing: A new frontier in layer-less 3D printing

Volumetric Additive Manufacturing (VAM) is an emerging 3D printing technology that operates by fabricating objects from all points within a medium 's volume. This technique is capable of producing parts without supporting structures and is capable of overprinting around existing structures. Notably, the approach that VAM utilises to print is time efficient compared to traditional additive manufacturing methods with printing times being measured in seconds and minutes instead of hours. As this is an emerging technique there is little comparison or synthesis reported so far in the literature, thus the primary objective of this review is to address this issue by providing a comprehensive analysis of VAM, delving into its applications, the challenges it faces, and the research advancements made in the area. This review also investigates how new methods of VAM are investigated and reported on, within the literature. In order to achieve this goal a structured literature review was conducted to thoroughly examine the current state of VAM. This review found 30 research papers, which were used to categorise different VAM methods, explore its potential in various fields, and formulate a definition for VAM to differentiate it from other additive manufacturing technologies. A key finding of this review is that while VAM offers rapid fabrication capabilities, it currently faces several constraints. These include a limited availability of commercial VAM printers, complex printing methodologies, a restricted range of compatible materials, and the need for specialised equipment. Collectively, these factors could serve as potential barriers to the broader adoption of this technology. In addition, there is a lack of homogeneity in the parameters used to investigate and report VAM which makes it difficult to compare and contrast new research works against existing published literature. As the field progresses, addressing these challenges will be essential to unlock new applications and increase adoption of this technology. This review is one of the first to explicitly focus on and address the entirety of VAM, offering valuable insights into the present state of VAM and directions for future research.