New volumetric additive techniques are overcoming traditional 3D printing’s layer-by-layer constraints. By projecting patterns into specially formulated resins, they can fabricate entire designs simultaneously through holographic and upconversion photoinitiation. This article analyzes the revolutionary implications of light-based volume manufacturing for industries seeking optimized fabrication outcomes.

Volumetric 3D Printing: Instantaneous Whole-Object Fabrication

Lawrence Livermore National Laboratory (LLNL) researchers have developed an innovative new 3D-печать method that utilizes holographic projection to fabricate objects quickly in a single step. Traditionally, 3D printing builds objects layer-by-layer which can be time-consuming for complex geometries. LLNL’s technique overcomes these limitations through a volumetric printing process inspired by medical imaging technologies.

The method works by using multiple lasers to project photonic patterns through a liquid photopolymer resin. These hologram-like images encoded with 3D object data are overlapped within the resin bath to simultaneously cure it into the desired solid structure. Where the projected laser beams intersect, the light intensity is highest and effectively ‘draws’ the object shape out of the liquid resin. This allows intricate designs to be fabricated rapidly without requiring layering or support materials.

How the Holographic Fabrication Process Works

Three laser sources project beams through different angles into the photopolymer vat containing the uncured resin solution. Digital holograms encoded with the 3D CAD file are used to spatially modulate each laser beam according to the object data. When the laser patterns intersect inside the resin bath, they add constructively to locally increase the total light intensity. This localized photopolymerization initiates curing of the molecular bonds within the resin wherever the light intensity exceeds the material’s activation threshold.

Gradually, the overlapping laser light draws out the 3D object geometry directly from the liquid into a solid structure. The process continues until the entire design is fabricated in a single shot. By projecting laser patterns from various angles, the technique achieves true volumetric printing without needing to build up layers or use supporting structures. Entire complex geometries can be produced within a matter of seconds versus hours required by conventional 3D printers.

Advantages over Traditional Layer-Based 3D-печать

Faster Printing for Complex Designs

Being able to print objects entirely at once provides a dramatic increase in print speeds compared to incremental layering methods. Complex geometries with interior structures, moving parts or topologically optimized designs can all be produced much faster without the time penalty of layer stacking. Medical and defense applications where swift manufacturing is essential can benefit greatly from this rapid volumetric approach.

No Support Structures Required

Without needing to build objects up from a base, overhangs, cavities and convoluted geometries can be freely designed without worry about support structure placement or removal. This significantly expands the range of printable shapes and simplifies post-processing. It also eliminates material waste from dissolved support supports and reduces costs.

Higher Resolution from Full Volume Curing

By curing the entire object volume simultaneously with projected light patterns, even subtle surface details can be faithfully replicated at the highest resolutions allowed by the laser setup and resin properties. This bests the layerwise curing methods where successively stacked films have differing exposures leading to z-axis elongation of features. Finer geometric detail is achievable through full-volume photopolymerization.

In summary, LLNL’s holographic 3D printing brings the advantages of projection technologies to stereolithography for a paradigm shift towards rapid, support-free fabrication of complex parts and devices. The method shows great promise for product design, biomedical implants, and industrial volume production where one-step printing can deliver substantial benefits over traditional layerwise processes. Continued refinements to resin formulations, optics and software will further advance this novel 3D printing approach.

Upconverting Resin for Stationary Volume Fabrication

Controlling Curing via Laser Scanning

Researchers at Harvard University have developed a new resin for 3D printing that contains upconverting nanoparticles. These nanoparticles are special in that they can absorb infrared light and re-emit it as higher energy blue light. When incorporated into a photosensitive resin, it allows curing to be activated by an infrared laser rather than ultraviolet light.

This has significant advantages for 3D printing. An infrared laser can be precisely focused into the resin vat to produce a tiny focal point of blue light via upconversion. By scanning the laser beam around inside the vat, this blue dot acts as a mobile “hotspot” that can selectively cure the resin wherever it strikes. This enables true volumetric printing without needing to build objects up layer-by-layer.

The 3D printing process works by loading the upconverting resin into the vat and using software to plan the laser scanning pathways according to a 3D model file. The laser then traces through these paths, causing local resin hardening at its focal point through upconversion and photoinitiation. Gradually, the entire object is fabricated simultaneously without requiring support structures. Even complex interior geometries and moving components can be produced in a single stationary print batch.

Applications and Future Development

This stationary volume printing method using an upconverting resin unlocked by infrared laser light offers several advantages over traditional layer-based 3D printing technologies:

• Vastly increased print speeds. Entire objects are fabricated at once rather than incrementally in layers, allowing production times measured in minutes instead of hours.
• No support structures. Overhangs, cavities or moving parts can be printed freely without temporary supports that require post-processing removal.
• Higher resolution details. The simultaneous curing throughout the object volume eliminates issues of z-axis feature deformation common in layered processes.

Initial applications could include rapid prototyping where speed is critical. Other uses involve precision dental models, medical implants with complex porous structures, and consumer product design with conformal cooling channels or nested parts.

Further development aims to refine the upconverting nanoparticle formulations to boost efficiency and lower laser power needs. Improving the 3D scanner and control software may allow printing finer geometric details at the limit of the laser’s focal width. New resins compatible with biological tissues could expand applications to regenerative medicine including 3D bioprinting.

In the future, instant 3D printing through upconversion promises to revolutionize how objects are manufactured layer-free and at the push of a start button. As technologies advance, stationary volume fabrication may replace conventional layer-wise 3D printing across many industries seeking greater build speeds and design freedom.

Combining Micro-CAL and Glass Resin

Researchers at the University of Tokyo have demonstrated a new technique for 3D printing microscopic glass structures using a laser-based micro-stereolithography system called micro-CAL (Continuous Activator and Liquid) combined with a specialized nano-composite glass resin.

In micro-CAL, a laser continuously scans within a liquid resin bath to locally catalyze solidification instead of building objects up layer-by-layer. For glass printing, the team formulated a hybrid resin made from inorganic nanoparticles dispersed in a photosensitive pre-ceramic polymer binder.

When the laser draws scanning patterns through this specialized glass resin using micro-CAL, it causes two photon polymerization which progressively cures the patterned resin. During post-processing heat treatment, the cured form decomposes and the inorganic filler consolidates to form solid transparent glass structures at micrometer scale resolutions.

High Resolution and Surface Quality Printing

The achieved resolution with micro-CAL 3D printing of glass significantly surpassed conventional additive manufacturing methods. Surface features as small as 50μm were reproducibly fabricated with surface roughness below 6nm over large areas, approaching the limits of optical components.

Complex 3D glass architectures such as spiral microlenses, Fresnel lenses and photonic crystals were printed, demonstrating the technique’s design flexibility. Unlike traditional lithography which can only produce 2D patterns, true 3D geometries were achieved in a single continuous process step.

Potential Applications and Impacts

This work opens new avenues for micro-optics fabrication. Areas like biomedical imaging, microfluidics and chemical sensing could leverage printed glass optics for lab-on-a-chip technologies. Other applications involve minimally invasive surgical devices, implantable optoelectronics and compact consumer products.

Adoption of micro-CAL 3D printing using a glass resin can transform capabilities across industries. Possibilities include customizable endoscopes, wearable displays, environmental sensors, and bioresearch platforms. Manufacturers may find new ways to integrate tunable photonics, microfluidic control and optical assays.

Continued developmental efforts aim to expand the glass material toolkit for specialized refractive indices and chemistries. Optimizing printing parameters toward even finer nanoscale resolution and throughput could catalyze disruptive innovations across science and technology.

Faster than Layer-Based 3D Printing

Volumetric 3D printing has emerged as a disruptive alternative to traditional layer-by-layer additive manufacturing. Both LLNL’s holographic lithography and Harvard’s upconversion-based method cure entire objects simultaneously, bypassing incremental layer stacking.

This allows production speeds measured in seconds rather than hours. LLNL projects holograms into a photopolymer resin, utilizing the combined laser interference patterns to rapidly cure complex designs. Harvard’s approach uses tunable upconverting nanoparticles sensitive to specific wavelengths within an infrared laser scanning system.

While both eliminate support structures and post-processing through stationary full-volume fabrication, each technique has unique advantages depending on the application. LLNL’s method offers wide material compatibility and high resolution capabilities suited for medical and industrial applications. Harvard’s upconversion resin system is well-suited for rapid prototyping and fabrication situations requiring fast print speeds under controlled laboratory conditions.

The difference in curing mechanisms and materials provide variable options to optimize for specific production needs based on design, resolution, throughput and processing environments.

Заключение

Volumetric 3D printing has made great strides in addressing many of the limitations of traditional layer-by-layer additive manufacturing. Methods like LLNL’s holographic lithography and Harvard’s upconversion-based approach demonstrate how projecting light patterns can fabricate complex shapes directly within photosensitive resins in a single swift step.

By eliminating incremental layer building, these technologies slash print times from hours down to mere seconds while removing constraints on geometric complexity. No longer are support structures necessary, expanding the possible range of designs. Simultaneous curing through resin volumes also improves resolution and surface quality.

While still in the research and development phase, real-world applications of stationary volume 3D printing are starting to emerge across industries like healthcare, consumer products and precision engineering. Further refining light sources, resins and process control will help maximize performance for specific manufacturing needs.

As volumetric additive techniques mature, they promise to upend traditional notions of 3D printing. The ability to print entire objects on demand at the push of a start button foreshadows a revolution in digital fabrication across supply chains both large and small. It marks an evolution towards truly instant production facilitated by new photonic materials and light-based 3D printing principles.

Вопросы и ответы

What are the key advantages of volumetric 3D printing?

Volumetric methods can fabricate complete objects simultaneously instead of incrementally layer-by-layer. This drastically reduces print times from hours to minutes while avoiding limitations on geometric complexity. Support structures are also unnecessary.

How do holographic and upconversion methods work?

Holographic lithography projects interference patterns into a photopolymer resin to rapidly cure designs. Upconversion uses nanoparticles to convert infrared light into localized blue light hotspots within a resin, guiding curing in 3D. Both fully solidify objects without layer-stacking.

What applications is it best for?

Volumes systems excel at rapid prototyping and manufacturing where speed is critical. Uses involve dental models, bioprinting, microfluidics, customized electronics and precision engineering. Refining resolution and materials could expand biomedical and optical device applications.

What are the main challenges to overcome?

Continued work is needed to increase resolution, develop specialized resins, enhance light sources and scanning systems, refine post-processing and scaling. Optimizing each component will help volume printing compete across more industries by enabling finer details and higher throughput.