Progress In 3D Printing Research Articles

Where digital meets physical innovation: Reverse salients and the unrealized dreams of3Dprinting

AbstractFor more than three decades, enthusiasts have predicted that direct manufacturing enabled by 3D printing would inevitably supplant traditional manufacturing methods. Alas, for nearly as long, these utopian predictions have failed to materialize. One reason is a flawed assumption that hybrid digital‐physical systems such as 3D printing would advance as rapidly as purely digital innovations enabled by Moore's law. Instead, like other examples of cyber‐physical systems (CPSs), technological progress in 3D printing faces inherent limitations that are emblematic of the differences between CPSs and purely digital innovations. As with any complex CPS, improved performance of a 3D printing system has been limited by that of its key components—the sort of limiting problem previously defined as a reverse salient. Unlike previously studied technologies, several reverse salients for 3D printing performance have neither resolved nor signs of resolving soon. Here we analyze these key reverse salients, and show how they have hampered the suitability of 3D printing for direct manufacturing and other predicted applications. We contrast predicted versus actual capabilities for 3D printing‐enabled transformation in six key areas: product innovation, mass customization, home fabrication, distributed manufacturing, supply chain optimization and business model innovation. From this, we suggest opportunities for greater realism in future 3D printing research, as well as broader implications for our understanding of CPSs and reverse salients.

3D printed graphene aerogels using conductive nanofibrillar network formulation

Despite recent progress in 3D printing of graphene, formulation of aqueous 3D printable graphene inks with desired rheological properties for direct ink writing (DIW) of multifunctional graphene macrostructures remains a major challenge. In this work, we develop a novel 3D printable pristine graphene ink in aqueous phase using conductive nanofibrillar network formulation by controlling the interfacial interactions between graphene and PEDOT:PSS nanofibrils. The formulated inks, tailored for energy applications, provide excellent 3D printability for fabricating multilayer 3D structures (up to 30 layers) with spanning features and high aspect ratio. The 3D printed aerogels, comprising interconnected networks of graphene flakes and PEDOT:PSS nanofibrils, exhibit excellent electrical conductivity as high as ∼630 S m − 1 and can be converted into conductive hydrogels via swelling in water/electrolyte. The formulated graphene inks were used for fabricating 3D printed supercapacitor electrodes (power density of 11.3 kW kg−1 and energy density of 7.3 Wh kg−1) with excellent performance and durability.

3D-printed design of a stereotaxic adaptor for the precision targeting of brain structures in infant mice.

Experimental investigation of early postnatal brain development in infant mice (<postnatal day 10) is challenging because of the rapid expansion of their brain volume and the fragility of cranial bones. Stereotaxic adaptors that are commercially available usually evoke significant compression forces, thus limiting the accuracy of micromanipulations. Here, we took advantage of recent progress in 3D printing for the cost-effective production of stereotaxic adaptors for infant mice. Our designs offer gentle head positioning, tailored incisor placement and high precision, while also integrating evaporator and tubing components for gaseous anaesthesia. Thus, post-procedural lethality is minimized even upon time-consuming surgeries. Viral microinjections through glass capillaries are shown as proof of principle to experimentally validate targeting accuracy in mice aged 6-10days. The exact engineering workflow and printing protocol are disseminated for open-label use. Overall, we present technical details and experimental data on a stereotaxic device that can help neurobiologists working at a particularly complex developmental stage in mice.

The Dorsal Skinfold Chamber as a New Tympanic Membrane Wound Healing Model: Intravital Insights into the Pathophysiology of Epithelialized Wounds

Background: Tympanic membrane perforations (TMPs) are a common complication of trauma and infection. Persisting perforations result from the unique location of the tympanic membrane. The wound is surrounded by air of the middle ear and the external auditory canal. The inadequate wound bed, growth factor, and blood supply lead to circular epithelialization of the perforation’s edge and premature interruption of defect closure. Orthotopic animal models use mechanical or chemical tympanic membrane laceration to identify bioactive wound dressings and overcome premature epithelialization. However, all orthotopic models essentially lack repetitive visualization of the biomaterial-wound interface. Therefore, recent progress in 3D printing of customized wound dressings has not yet been transferred to the unique wound setup of the TMP. Here, we present a novel application for the mice dorsal skinfold chamber (DSC) with an epithelialized full-thickness defect as TMP model. Methods: A circular 2-mm defect was cut into the extended dorsal skinfold using a biopsy punch. The skinfold was either perforated through both skin layers without prior preparation or perforated on 1 side, following resection of the opposing skin layer. In both groups, the wound was sealed with a coverslip or left unclosed (n = 4). All animals were examined for epithelialization of the edge (histology), size of the perforation (planimetry), neovascularization (repetitive intravital fluorescence microscopy), and inflammation (immunohistology). Results: The edge of the perforation was overgrown by the cornified squamous epithelium in all pre­parations. Reduction in the perforation’s size was enhanced by application of a coverslip. Microsurgical preparation before biopsy punch perforation and sealing with a coverslip enabled repetitive high-quality intravital fluorescence microscopy. However, spontaneous reduction of the perforation occurred frequently. Therefore, the direct biopsy punch perforation without microsurgical preparation was favorable: spontaneous reduction did not occur throughout 21 days. Moreover, the visualization of the neovascularization was sufficient in intravital microscopy. Conclusions: The DSC full-thickness defect is a valuable supplement to orthotopic TMP models. Repetitive intravital microscopy of the epithelialized edge enables investigation of the underlying pathophysiology during the transition from the inflammation to the proliferation phase of wound healing. Using established analysis procedures, the present model provides an effective platform for the screening of bioactive materials and transferring progress in tissue engineering to the special conditions of tympanic membrane wound healing.

Topological photonics in 3D micro-printed systems

Topological materials have been at the forefront of research across various fields of physics in hopes of harnessing properties such as scatter-free transport due to protection from defects and disorder. Photonic systems are ideal test beds for topological models and seek to profit from the idea of topological robustness for applications. Recent progress in 3D-printing of microscopic structures has allowed for a range of implementations of topological systems. We review recent work on topological models realized particularly in photonic crystals and waveguide arrays fabricated by 3D micro-printing. The opportunities that this technique provides are a result of its facility to tune the refractive index, compatibility with infiltration methods, and its ability to fabricate a wide range of flexible geometries.

GELMA BASED 3D BIOPRINTING IN REGENERATIVE MEDICINE

Over the past few years, research and progress in 3D printing have become evident. The process of bioprinting involves the use of a bioink composed of human cells or tissue. For example, 3D printing in organ transplantation aims to develop an organ that can synchronize with other physiologic components. In the past ten years, bioprinting has made a substantial leap. It has been used in the fabrication of living tissues for its application in various areas. Moreover, this technology has also been commercialized, resulting in its significant interest from the research fraternity. Thus, this review provides a brief on the development of the field from its foundation to the current commercialization with respect to the polymer Gelatin Methacrylate.&#x0D; Keywords: 3D Bioprinting, Stem cells, GelMA, Regenerative Medicine

Fabrication and characterization of titanium-alloy 3D printed solenoid inductors and their sensor applications

Recent progress in 3D printing has brought many interests in developing functional devices in various applications by enabling the exploration of complex 3D structures. This paper presents the first fully metal printed standalone 3D solenoid microinductors using a high-power laser with a biocompatible Ti-alloy. Fine powder-based 6AL-4V Eli Titanium was directly printed using an automated gantry laser system with 60 μm resolution to form the inductors without any substrate. A substrate-less 10-turn solenoid as a testbed was printed out and characterized, and additional designs of 20 and 40 turn inductors were further explored. The wire of the inductor was designed to have a 700-micron square cross-section and a winding gap of 300 microns. The successfully fabricated 10-turn titanium-alloy solenoid inductor showed an average inductance of 130 nH, a low-frequency resistance of 0.8 ohms at 0.3 MHz, and a quality factor of 10.5 at 30 MHz respectively. Additional electrodeposition of copper to the 10-turn inductor demonstrated process compatibility with the conventional micromachining process. The standalone inductor printing method saves a significant volume from where the conventional substrate dimensions often take more than the volume of the device. Also, the standalone inductor can directly be used as a sensor device. Examples of force-displacement sensing applications were presented using the 10-turn and 19-turn round edge solenoid inductors.

Recent Progress in 3D Printing of Bioinspired Structures

Over millions of years of evolution, the species in nature have gradually possessed some bio-structures. These structures have specific mechanical, hydrodynamic, optical, and electrical properties, which provide human the valuable enlightenments to design and fabricate high-performance components and devices. However, the traditional fabrication technologies cannot accurately reproduce or imitate the complicated and exquisite bioinspired structures, which restricts the development and application of biomimetic study. Due to the emergence and development of 3D printing technologies, more bioinspired structures can be designed and fabricated. Recent progress in 3D printing of structures inspired by the species in nature, such as springtails, filefish, abalone shell, conch shell, wheat awn, plant stem and wood, etc., are reviewed in this paper and the current challenge and future development for 3D printing of bioinspired structures are discussed.

Optimal design of helical heat/mass exchangers under laminar flow: CFD investigation and correlations for maximal transfer efficiency and process intensification performances

Highly curved helical pipes (HCHPs) offer tremendous potentialities for intensified heat/mass transfer performances as they generate intense Dean-type vortices. However, these designs have not been explored so far in the literature, probably because they are difficult to build using traditional manufacturing techniques. Nowadays, thanks to a witnessed progress in 3D-printing, the fabrication of HCHPs has become achievable. Therefore, investigating their performance in terms of heat and mass transfer intensification presents significant interest from both academic and industrial points of view.In this paper, CFD simulations are carried out to determine the heat/mass transfer efficiency in helical pipes (particularly highly curved ones) under laminar flow conditions. The packing density (i.e. interfacial area) of these geometries is evaluated using a CAD software. The results reveal that HCHPs not only allow achieving much higher transfer rates than straight and classical helical pipes, but they can also be densely packed. Therefore, when appropriate designs are selected, impressive process intensification factors are achievable, with up to 8-fold volume reductions.Finally, correlations are developed for evaluating the interfacial area and the heat/mass transfer efficiency in classical and highly curved helical pipes. In future works, these correlations will be used in model-based optimization for determining the optimal designs of helically coiled heat/mass exchangers.

3D printing, international trade, and FDI

We analyze the relationship between 3D printing technology, the volume of trade, and the structure of foreign direct investment (FDI). We present a standard trade model with firm-specific heterogeneity into which we include 3D printing as a technology choice for foreign direct investment. The model generates three predictions. First, 3D printers are introduced in areas with high economic activity that face high transport costs. Second, technological progress in 3D printing leads to FDI dependent on traditional techniques gradually being replaced by FDI based on 3D printing. Third, with wider adoption, further technological progress in 3D printing leads to a gradual replacement of international trade. Empirical evidence focusing on the sectors with the highest rates of adoption supports the first hypothesis, while evidence from a case study supports the second and third. Our results suggest that the traditional strategy of poor countries for export-led industrialization is threatened by the widespread adoption of 3D printing that replaces international trade.

3D printed electrochemical energy storage devices

Recent progress in 3D printing of electrochemical energy storage devices.

3D bioprinting: an emerging technology full of opportunities and challenges

Three-dimensional (3D) printing is a novel promising technology based on 3D imaging and layer-by-layer additive fabrication. It has a profound influence on all aspects of our lives and is playing an increasing important role in many areas including engineering, manufacturing, art, education and medicine. “3D bioprinting” has been put forward with the technical progress in 3D printing and might be a possible way to solve the serious problem of human organ shortage in tissue engineering and regenerative medicine. Many research groups flung them into this area and have already made some gratifying achievements. However, it is a long way to fabricate a live organ. Many elements lead to the limitation of 3D bioprinting. This review introduces the background and development history of 3D bioprinting, compares different approaches of 3D bioprinting and illustrates the key factors of the printing process. Meanwhile, this review also points out existing challenges of 3D bioprinting and has a great prospect. Some points proposed in this review might be served as reference for the research of this field.

The Impact of 3D Printing on Trade and FDI

This paper analyzes the effects of 3D printing technologies on the volume of trade and on the structure of FDI. A standard model with firm-specific heterogeneity generates three main predictions. First, 3D printers are introduced in areas with high economic activity that also face high transport costs. Second, technological progress related to 3D printing machines leads to a gradual replacement of FDI that relies on traditional production structures with FDI based on 3D printing techniques. At this stage international trade stays unaffected. Finally, at later stages, with 3D printing machines being widely used, further technological progress in 3D printing leads to a gradual replacement of international trade. Empirical evidence indicates that countries subject to higher transport costs and with high levels of economic activity are indeed among the ones that import more 3D printers. Anecdotal evidence also supports the second and third predictions of the model.