Page 10 - MSAM-3-2

Materials Science in Additive Manufacturing Functional materials for AM

through small nozzles to create desired shapes. This difference from SLA lies in the light source. While SLA
process involves the extrusion of material in a continuous employs rastering lasers, DLP utilizes a projector light
stream rather than layer-by-layer deposition typical of source, enabling a different approach to layer creation.
other 3D printing methods. DIW allows for the use of A defining advantage of DLP is its capability to print an
various materials, including non-thermoplastic polymers, entire 2D layer simultaneously, thanks to the digital micro-
hydrogels, ceramics, and even living cells, in bio-printing mirror device generating a digital image to illuminate each
27
applications. The ability to print with liquid materials layer’s shape in one go. This simultaneous curing process
provides flexibility in material composition and properties, contributes to the rapid production of high-resolution
making DIW suitable for a wide range of applications in models, distinguishing DLP for its speed in manufacturing.
fields such as biomedicine, soft robotics, and electronics. 21,22 This speed advantage positions DLP as a viable choice
for applications where time-to-market is crucial, such as
Meniscus printing is a 3D printing technology wherein
liquid polymers are dispensed onto a flat surface and precision parts manufacturing and medical modeling.
shaped using surface tension to achieve the desired form. However, it is worth noting that compared to SLA, DLP
This method typically involves the controlled deposition may exhibit slightly lower resolution due to the nature of
of droplets of liquid polymer onto a substrate. The surface its projection method. Despite this minor drawback, DLP’s
efficiency in printing speed makes it an attractive option
tension of the liquid causes it to form a meniscus, which for various industries seeking to balance between speed
can be controlled to create precise shapes and structures. 23,24 and resolution in their AM processes.
Meniscus printing offers advantages in producing complex
geometries and structures with high resolution and Continuous liquid interface production (CLIP) 3D
precision. It finds applications in various fields, including printing is an AM technology that addresses the slow
biomedicine, where it can be used to create biomaterials production speed of SLA and DLP by fundamentally
for tissue engineering and drug delivery systems. changing the manufacturing process. Instead of layer-
by-layer manufacturing using photo-curable resin, CLIP
2.2. Vat photopolymerization continuously lowers a liquid resin pool to manufacture
28
Vat photopolymerization is an AM technology that objects. This continuous process offers significantly faster
selectively solidifies liquid resin contained in a vat production speeds, up to 100 times faster than conventional
using a curing device. The liquid resin typically consists layer-by-layer methods, while maintaining high accuracy.
of oligomers and monomers. When exposed to the CLIP holds promise for manufacturing innovation due to
curing light, the oligomers and monomers undergo its speed and precision, opening up new possibilities for
polymerization, forming polymer chains that harden to various industries. The primary distinction between DLP
create the desired object. The curing process occurs layer and CLIP lies in their manufacturing processes: CLIP utilizes
by layer, with each layer solidified before the next layer a continuous manufacturing process, whereas DLP employs
is added, resulting in precise and detailed models. Vat a layer-by-layer approach, as illustrated in Figure 2B.
photopolymerization utilizes various curing devices such as 2.3. Binder jetting
UV beams, digital light, and light-emitting diodes (LEDs),
offering advantages in high resolution and accuracy for the Binder jetting is an AM process that begins by evenly
resulting products. 25 spreading powder material across a build platform.
Subsequently, a binder, typically in liquid form, is precisely
Stereolithography (SLA) is a high-resolution jetted onto the powder layer, selectively solidifying it. This
AM technology that employs rastering lasers to process is repeated for each layer until the desired object is
photopolymerize liquid resin, forming 3D models. The formed. The schematic of the binder jetting process is depicted
process involves sequentially exposing the resin surface to in Figure 2C. Post-processing techniques such as sintering or
the laser to create layers, with each layer cured by UV light. infiltrating can, further, enhance the precision and strength
26
A schematic diagram of the SLA process is illustrated on of the final product. Binder jetting is known for its relatively
the left in Figure 2B. SLA is capable of producing intricate high production speeds and cost-effectiveness, making it
and complex models with high precision. It finds extensive suitable for mass production. In addition, its ability to mix
applications in industries such as advanced medical, various materials provides versatility for manufacturing
automotive, and aerospace due to its ability to fabricate functional components across different industries. 26
precise and complex prototypes and functional parts.
Digital light processing (DLP) stands out in the realm 2.4. PBF
of AM as a technology that precisely photopolymerizes Polymer materials are primarily utilized in the PBF process,
liquid resin using a projector light source. Its significant predominantly through selective laser sintering (SLS).

Volume 3 Issue 2 (2024) 4 doi: 10.36922/msam.3323