Andrew J. Boydston is the Yamamoto Family Professor of Chemistry at the University of Wisconsin-Madison. As a trained chemist he worked on catalysts for the synthesis of polymers during his postdoc time and started his independent career as an assistant professor of Chemistry in 2010 at the University of Washington. In 2014 he involved in a project with colleagues at the mechanical engineering department at the University of Washington which piqued his interest in additive manufacturing and which remained one of his research lines after moving to the University of Wisconsin-Madison in 2018. He is interested in organocatalysts for polymerization reactions, mechanophores, polymers for controlled release and additive manufacturing.
Additive Manufacturing and 3D Printing
Bespoke manufacturing by design and on-demand is the ultimate goal for various fields ranging from biomaterials to structural materials. Today, additive manufacturing is a quick-moving, interdisciplinary research field. In this collection, we highlight some of the experimental and theoretical work around this topic published in Nature Communications. Discover the latest research on printing methods, devices, materials development and on advancing the printing process and post-process modifications.
Advances in inks, printing resolution, and printing methods
3D printing of metals produces elongated columnar grains which are usually detrimental to component performance. Here, the authors combine ultrasound and 3D printing to promote equiaxed and refined microstructures in a titanium alloy and a nickel-based superalloy resulting in improved mechanical properties.
Additive manufacturing technologies provide versatility but are limited in terms of printing speed and resolution. Here the authors demonstrate printing of 3D structures with submicrometer features by electrostatically deflecting a jet in electrohydrodynamic jetting.
Tomographic additive manufacturing produces complex parts with a wide range of printable materials but remains limited in terms of resolution. Here, the authors tune the étendue of the light source and accurately control the photopolymerization kinetics using an integrated feedback system, leading to the fabrication of high resolution features.
Inkfree multi-material printing is a common challenge in 3D printing. Here, the authors introduce electrohydrodynamic redox printing, a method that enables the deposition of multiple metals and their alloys with nanoscale resolution and thus the synthesis of materials with locally tuned properties.
Additive manufacturing of high entropy alloys is still an emerging field that usually relies on expensive pre-alloyed powders. Here, the authors develop a method to 3D ink-print a CoCrFeNi high entropy alloy using inexpensive blended oxide nanopowders, hydrogen reduction, and sintering.
Two photon polymerization (TPP) allows nanofabrication of three dimensional objects with complex geometries, but is considered to be slow with a limited fabrication rate. Here the authors present a TPP technique based on a digital mirror device scanner which allows for fast parallel nanofabrication with improved precision and flexibility.
Objects with varied mechanical properties can be produced by additive manufacturing, but multimaterial control along all three axes of printing is still limited. Here the authors use wavelength control during vat polymerization and demonstrate printing of objects with spatial control of the composition and stiffness.
Printing functional inks is attractive for applications in electrochemical energy storage and smart electronics, among others. Here the authors report highly concentrated, additive-free, aqueous and organic MXene-based inks that can be used for high-resolution extrusion and inkjet printing.
Although 3D bioprinting technology has gained much attention in the field of tissue engineering, there are still several significant challenges that need to be overcome. Here, the authors present silk fibroin bioink with printability and biocompatibility suited for digital light processing 3D printing.
Atomically thin black phosphorus shows promise for optoelectronics and photonics, yet its instability under environmental conditions and the lack of well-established large-area synthesis protocols hinder its applications. Here, the authors demonstrate a stable black phosphorus ink suitable for printed ultrafast lasers and photodetectors.
Ultrafast laser processing is a versatile three-dimensional photonic structuring method but it has been limited to wide band gap materials like glasses. Here, Chanal et al. demonstrate direct refractive-index modification in the bulk of silicon by extreme localization of the energy deposition.
Endowing composite materials with spatially discrete mechanical behaviours is possible by varying the internal concentration and arrangement of particles. Here, the authors demonstrate a 3D magnetic printing technique which enables the fabrication of materials with intricate internal designs.
The application of 3D printing to biomaterials presents interesting possibilities for tissue engineering. Here, the authors show that a printing medium derived from an extracellular matrix can be applied to printing tissue analogues with enhanced cell compatibility.
Biological, electronic, and robotic devices
Robert S. Langer is an Institute Professor at the Massachusetts Institute of Technology. Leading one of the largest biomedical engineering labs in the world his research covers many areas of biotechnology including tissue engineering, drug delivery, biofabrication and the development of medical devices. Mark Tibbitt is an Assistant Professor of Macromolecular Engineering at ETH Zürich. His research focuses on combining polymer engineering, synthetic chemistry, mechanical and bioengineering for biofabrication, drug delivery and mechanobiology applications.
Corals have evolved as finely tuned light collectors. Here, the authors report on the 3D printing of coral-inspired biomaterials, that mimic the coral-algal symbiosis; these bionic corals lead to dense microalgal growth and can find applications in algal biotechnology and applied coral science.
Neural cell integration into 3D bioprinted skeletal muscle constructs accelerates restoration of muscle function
3D bioprinting of skeletal muscle using primary human muscle progenitor cells results in correct muscle architecture, but functional restoration in rodent models is limited. Here the authors include human neural stem cells into bioprinted skeletal muscle and observe improved architecture and function in vivo.
A major challenge in 3D printing is the creation of hollow tubular structures. Here, the authors report on a solid particulate support for patterning a hydrogel with bacteria that produces cellulose in an oxygen dependent manner, using air diffusion through the particulate support to create hollow cellulose tubes.
Harnessing liquid-in-liquid printing and micropatterned substrates to fabricate 3-dimensional all-liquid fluidic devices
Non-equilibrium systems of immiscible liquids have significant potential to advance different technologies, but control over morphology or functionality remains unexplored. Here, the authors demonstrate an all-liquid fluidic device by exploiting surfactant assemblies to produce a semi-permeable membrane between the liquids.
The development of novel low-cost fabrication schemes for realizing stretchable transistor arrays with applicability in wearable electronics remains a challenge. Here, the authors report skin-like electronics with stretchable active materials and devices processed exclusively from ink-jet printing.
Mechanical computing based on the logic devices that utilize mechanical energy can be an alternative to conventional electronic computing. Here, Song et al. show a micromechanical logic gate, fabricated using multi-stable buckling flexures, which is capable of realizing all digital logic operations.
Rapid fabrication of reinforced and cell-laden vascular grafts structurally inspired by human coronary arteries
Bioengineering of small diameter vascular grafts that recapitulate the features of native vessels is extremely challenging. Here the authors present a combined dip-spinning and blow-spinning technology to fabricate multi-layered cell-embedded grafts with native mechanical properties.
The ability to print arbitrary colors and shapes in all three dimensions at microscopic length scales is still lacking. Here, the authors introduce a means to produce three-dimensionally-printed photonic crystals with a periodicity as small as 280 nm, achieving sub-100-nm features with a full range of colors.
Integrating cell-laden hydrogels effectively into the 3D printing process is a challenge in the creation of tissue engineering scaffolds. Here, the authors describe an additive manufacturing technique to combine polymer and cell-containing networks with 3D-printed mechanical supports.
3D-printed soft actuators have limited motion and are far from reaching the level of complexity found in biological systems. Here the authors present a multimaterial 3D printing platform for the fabrication of soft actuators displaying a wide range of motions that are programmable.
A bioprosthetic ovary created using 3D printed microporous scaffolds restores ovarian function in sterilized mice
There is a clinical need to develop a bioengineering system to support ovary transplantation. Here, the authors generate a bioprosthetic ovary using 3D printed scaffolds of varying pore architectures to support follicle survival and ovarian function in sterilized mice.
Nanoparticles capable of selectively binding target chemicals have potential for detoxification processes, but can lead to accumulation in the liver. Here the authors show a 3D-printed device containing functional nanoparticles, allowing the detox potential to be realised while holding the particles in place.
Modulating materials properties using 3D printing
Professor Julia R Greer is a materials scientist at the
The development of artificial 3D soft materials and device systems that can reproduce the nonlinear, anisotropic mechanical properties of biological tissues remains challenging. Here, the authors design a class of soft 3D network materials that can offer defect-insensitive, nonlinear mechanical responses closely matched with those of biological tissues.
Shape-morphing materials from initially flat to curved surfaces don’t tend to account for the rates of shape transformation. Here, the authors develop an algorithm for design and fabrication of plates that morph in water taking the desired 3D shape with deformation rates specified across the surface.
Flexible thermoelectric composite threads are reported for wearable thermal energy harvesting platforms where rigid materials lack compatibility. Thermoelectric thread modules are demonstrated, and pressure-dependence shows thread compression to be essential for improving electrical conductivity.
Incorporating and dispersing dense nanoparticles into metals remains a challenge. Here, the authors use nanocomposite powders containing very dense nanoparticles to print an aluminium nanocomposite with one of the highest specific modulus and yield strength among all structural materials.
Though additive manufacturing methods are highly attractive for the high-throughput fabrication of 3D electronic materials and devices, printing multimaterial devices remains a serious challenge. Here, the authors report optoelectronic multimaterial filaments for 3D-printed optoelectronics.
Fabrication of arbitrary three-dimensional suspended hollow microstructures in transparent fused silica glass
Fused silica glass has excellent optical properties, chemical and thermal stability and hardness, but its microstructuring for miniaturized applications has proven difficult. Here the authors demonstrate obtainment of precise arbitrary three dimensional hollow microstructures in fused silica glass by sacrificial template replication.
Stimuli-responsive microstructures are important in soft robotics and biosciences, but water compatible materials to fabricate 3D structures are scarce. Here, the authors demonstrate pNIPAM based hetero-microstructures with substantially different material parameters by variation of the local exposure dose in 3D laser lithography.
Spatially controlled expansion and contraction of soft tissues to achieve complex three dimensional morphologies remains challenging in man-made materials. Here the authors demonstrate encoding of 2D hydrogels with spatially and temporally controlled growth to create dynamic 3D structures.
3D printing of titanium alloys today is based on known alloy compositions that result in anisotropic structural properties. Here, the authors add lanthanum to commercially pure titanium and exploit a solidification path that reduces texture and anisotropy.
Most current methods for additive manufacturing of complex metallic 3D structures are limited to a resolution of 20–50 µm. Here, the authors developed a lithography-based process to produce 3D nanoporous nickel nanolattices with octet geometries and a resolution of 100 nm.
Superior mechanical properties in natural composites are frequently achieved by the inclusion of locally orientated reinforcing particles. Here, the authors implement this design strategy synthetically by employing a 3D magnetic printing protocol to create programmable composite architectures.
Aerogels are ultra-lightweight porous materials that possess some remarkable properties. Here, the authors use a 3D printing technique to fabricate just such a material out of graphene, exhibiting large surface area, high conductivity and supercompressibility while maintaining good structural integrity.
Insights into 3D printing processes and post-processing
Professor Peter D Lee is a materials scientist at the
Three-dimensional (3D) hydrogel printing enables production of volumetric architectures but achieving good resolutions for miniaturized features remains challenging. Here the authors demonstrate shrinking of a printed structure by immersing a 3D-printed patterned hydrogel consisting of a hydrophilic polyionic polymer network in a solution of polyions of the opposite net charge.
Understanding metal component microstructure during 3D printing remains a challenge. Here, the authors use local thermal parameters and the solidification microstructure to better understand how the printed microstructure varies with the laser scan strategy.
The impact of grain-scale residual stresses on the mechanical behaviour of 3D-printed metals and alloys remains unexplored. Here, the authors combine in situ synchrotron X-ray diffraction and computer simulations to link residual stresses in steel to its tensile behaviour.
3D printing pore-free complex metal parts remains a challenge. Here, the authors combine in-situ imaging and simulations to show thermocapillary force can eliminate pores from the melt pool during a laser powder bed fusion process.
Advances in biofabrication technology enable 3D printed constructs to resemble real tissues, but it remains unclear how cell-generated forces deform these constructs. Here the authors investigate mechanical behaviours of 3D printed “microbeams” made from mixtures of living cells and extracellular matrix.
Laser-matter interactions during laser powder bed fusion additive manufacturing remain poorly understood. Here, the authors combine in situ X-ray imaging and finite element simulations to show how detrimental pores form under printing conditions and develop a strategy to suppress them.
Understanding what happens to the liquid in melt pools during welding and metal-based additive manufacturing remains a challenge. Here, the authors directly image internal melt pool dynamics using synchrotron radiation to show surface tension affects flow speed, orientation and surface turbulence.
Orthogonal programming of heterogeneous micro-mechano-environments and geometries in three-dimensional bio-stereolithography
Tuning the mechanical properties of extracellular matrix is of great interest in tissue engineering but spatial control over stiffness in hydrogels has been demonstrated in two dimensions only. Here the authors developed a layer-by-layer printing technique which uses oxygen inhibition to control the heterogeneous stiffness in 3D printed structures.
Subtractive manufacturing of microstructures is important for many applications, yet photoresists for 3D laser lithography allow only removal after development under harsh cleavage conditions. Here, the authors introduce a set of chemoselective cleavable photoresists allowing the orthogonal cleavage of microstructures under mild conditions.
Detrimental serrated plastic flow via dynamic strain aging (DSA) in conventionally processed nickel superalloys usually occurs during high temperature deformation. Here, the authors suppress DSA via a unique microstructure obtained using additive manufacturing and propose a new dislocation-arrest model in nickel superalloys.
Thermosetting polymers are widely used in 3D printing owing to their superior mechanical stability, but once they are printed, the highly crosslinked polmyers cannot be reprocessed or repaired. Here the authors demonstrate a two-step polymerization strategy toward 3D printing of reprocessable thermosets.
Additive manufacturing of metals is now widely available, but the interaction of the metal powder with the laser remains unclear. Here, the authors use X-rays to image melt features and pore behaviour during laser melting of powders.