Digital Light Processing: A Review on the Printing Resolution and the Materials Options

Abstract

Digital light processing (DLP) is a 3D printing technology that utilises a patterned light field to print 3D objects layer by layer, with fine features and reasonable scales. Due to the requirements in terms of functionalities, there are critical needs to print structures with finer features and broader materials options. This review focuses on the factors that are limiting these two perspectives. Techniques and recent progress to overcome challenges will be discussed as well. In the end, a brief outlook is given to motivate future research of DLP.

3D Printing of Green and Renewable Polymeric Materials: Toward Greener Additive Manufacturing

“…The photopolymerizable resin that is required by DLP/SLA 3D printing must have the ability to cross-link upon irradiation (typically visible light) into a solid or highly viscous prototype, be compatible with the specific wavelength of light, and possess rheological characteristics allowing for layer deposition to form a cohesive prototype. ,,− For the viscosity to be sufficiently low, at room temperature, for use as an effective DLP/SLA resin, polymer molecular weights typically range from 0.6 kDa to 3.0 kDa . However, this carries the disadvantage of a brittle final product due to high cross-linking density .…”

“…These parameters include the wavelength of the light that will excite the photoinitiator used (such as Irgacure 819), or induce a free radical polymerization mechanism as well as the ability of the light to penetrate the resin. 169 This will then affect the layer height achievable for each layer during the print and the overall quality/resolution of the final part. Additionally, the translucency of the resin will affect the penetration ability of the light, as well as the speed with which the part will be produced, since a longer exposure time will be required for the light to induce the necessary cross-linking to produce the solid part.…”

“…The printing parameters are closely tied to and often dictated by the physical properties of the material being printed. These parameters include the wavelength of the light that will excite the photoinitiator used (such as Irgacure 819), or induce a free radical polymerization mechanism as well as the ability of the light to penetrate the resin . This will then affect the layer height achievable for each layer during the print and the overall quality/resolution of the final part.…”

The rise of mechanical metamaterials: Auxetic constructs for skin wound healing

“…Their application to additive manufacturing has been growing and becoming common in recent years due to its high performance in terms of resolution, printing speed, scalability, and material versatility, as it can be applied to soft materials like polymers and hydrogels, but also to metals and ceramics. [130][131][132][133][134][135][136] In DLP applied to scaffold fabrication, a digital light projector is used to shine a pattern of light onto a photosensitive material solution, which contains a base-material, such as a hydrogel or a gelatin, and a photoinitiator, which reacts when exposed to the light, thus controlling the base-material solidification. 137 The light pattern is produced by a digital micromirror device (DMD) consisting of an array of micromirrors capable of changing their orientation via micro-actuators controlled by computer that allow them to reflect the light onto the material or onto an outer zone, where it is absorbed to prevent other surface reflections that could affect the precision of the fabrication process.…”

“…Their application to additive manufacturing has been growing and becoming common in recent years due to its high performance in terms of resolution, printing speed, scalability, and material versatility, as it can be applied to soft materials like polymers and hydrogels, but also to metals and ceramics. 130 – 136 …”