《3D打印》:将想象变成现实

你．需要一把功能强大的锤子吗？你需要一双精致无比的鞋子吗？你需要给孩子准备奇异的玩具吗？你需要一顿丰盛的晚餐吗？只管打印出来就行了，此书带你走进3D打印的世界，认识当下这个最酷的东西——它将从想象变成现实，并带来一场深刻的社会革命。

Effect of fractures on mechanical behavior of sand powder 3D printing rock analogue under triaxial compression

In practical engineering applications,rock mass are often found to be subjected to a triaxial stress state.Concurrently,defects like joints and fractures have a notable impact on the mechanical behavior of rock mass.Such defects are identified as crucial contributors to the failure and instability of the surrounding rock,subsequently impacting the engineering stability.The study aimed to investigate the impact of fracture geometry and confining pressure on the deformation,failure characteristics,and strength of specimens using sand powder 3D printing technology and conventional triaxial compression tests.The results indicate that the number of fractures present considerably influences the peak strength,axial peak strain and elastic modulus of the specimens.Confining pressure is an important factor affecting the failure pattern of the specimen,under which the specimen is more prone to shear failure,but the initiation,expansion and penetration processes of secondary cracks in different fracture specimens are different.This study confirmed the feasibility of using sand powder 3D printing specimens as soft rock analogs for triaxial compression research.The insights from this research are deemed essential for a deeper understanding of the mechanical behavior of fractured surrounding rocks when under triaxial stress state.

《3D打印技术应用》课程项目化改革的实践与探索

《产品快速成型-3D打印技术应用》课程是工业设计专业的基础课程之一。通过对本课程的学习,学生能了解快速成型的原理及各种成熟的快速成型技术,为将来进入专业工作岗位积累知识和经验。为了改变传统的理论课程教学模式,提高学生的实际应用能力,文章对该课程进行项目化教学改革进行了实践与探索,通过深入分析课程目标,开展项目设计,精心选取与课程相关实践性强的项目开展教学实践,并对项目化改革作出评价,以期提高学生的积极性和综合能力,使《3D打印技术应用》课程教学效果得到显著提升。

Composite bioabsorbable vascular stents via 3D bio-printing and electrospinning for treating stenotic vessels

A new type of vascular stent is designed for treating stenotic vessels. Aiming at overcoming the shortcomings of existing equipment and technology for preparing a bioabsorbable vascular stent （BVS）, a new method which combines 3D bio-printing and electrospinning to prepare the composite bioabsorbable vascular stent （CBVS） is proposed. The inner layer of the CBVS can be obtained through 3D bio- printing using poly-p-dioxanone （PPDO）. The thin nanofiber film that serves as the outer layer can be built through electrospinning using mixtures of chitosan-PVA （poly （vinyl alcohol））. Tests of mechanical properties show that the stent prepared through 3D bio-printing combined with electrospinning is better than that prepared through 3D bio- printing alone. Cells cultivated on the CBVS adhere and proliferate better due to the natural, biological chitosan in the outer layer. The proposed complex process and method can provide a good basis for preparing a controllable drug-carrying vascular stent. Overall, the CBVS can be a good candidate for treating stenotic vessels.

Visual representation and characterization of three-dimensional hydrofracturing cracks within heterogeneous rock through 3D printing and transparent models

The heterogeneity of unconventional reservoir rock tremendously affects its hydrofracturing behavior. A visual representation and accurate characterization of the three-dimensional （3D） growth and distribution of hydrofracturing cracks within heterogeneous rocks is of particular use to the design and implementation of hydrofracturing stimulation of unconventional reservoirs. However, because of the difficulties involved in visually representing and quantitatively characterizing a 3D hydrofracturing crack-network, this issue remains a challenge. In this paper, a novel method is proposed for physically visualizing and quantitatively characterizing the 3D hydrofracturing crack-network distributed through a heterogeneous structure based on a natural glutenite sample. This method incorporates X-ray microfocus computed tomography （μCT）, 3D printing models and hydrofracturing triaxial tests to represent visually the heterogeneous structure, and the 3D crack growth and distribution within a transparent rock model during hydrofracturing. The coupled effects of material heterogeneity and confining geostress on the 3D crack initiation and propagation were analyzed. The results indicate that the breakdown pressure of a heterogeneous rock model is significantly affected by material heterogeneity and confining geostress. The measured breakdown pressures of heterogeneous models are apparently different from those predicted by traditional theories. This study helps to elucidate the quantitative visualization and characterization of the mechanism and influencing factors that determine the hydrofracturing crack initiation and propagation in heterogeneous reservoir rocks.

A Review on the 3D Printing of Functional Structures for Medical Phantoms and Regenerated Tissue and Organ Applications

Medical models, or ＂phantoms,＂ have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification and validation, and medical devices development. Such new applications demand high-fidelity, patient-specific, tissue-mimicking medical phantoms that can not only closely emulate the geometric structures of human organs, but also possess the properties and functions of the organ structure. With the rapid advancement of three-dimensional （3D） printing and 3D bioprinting technologies, many researchers have explored the use of these additive manufacturing techniques to fabricate functional medical phantoms for various applications. This paper reviews the applications of these 3D printing and 3D bioprinting technologies for the fabrication of functional medical phantoms and bio-structures. This review specifically discusses the state of the art along with new developments and trends in 3D printed functional medical phantoms （i.e., tissue-mimicking medical phantoms, radiologically relevant medical phantoms, and physiological medical phantoms） and 3D bio-printed structures （i.e., hybrid scaffolding materials, convertible scaffolds, and integrated sensors） for regenerated tissues and organs.

High pressure EIGA preparation and 3D printing capability of Ti-6Al-4V powder

Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,along with the mechanical properties of the as-fabricated block by laser melting deposition(LMD),were investigated.The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400μm,and the median powder size(d50)decreases with increasing gas pressure.The powders with a size fraction of 100-150μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability.The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%-0.20%.Specimens fabricated by LMD are mainly composed ofα+βgrains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength(UTS)and yield strength of approximately 1100 and 1000 MPa,respectively.Furthermore,the atomized powders have a favorable 3 D printing capability,and the mechanical properties of Ti-6 Al-4 V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.

Indirect 3D printed ceramic:A literature review

Additive manufacturing(AM),also known as 3D-printing(3DP)technology,is an advanced manufacturing technology that has developed rapidly in the past 40 years.However,the ceramic material printing is still challenging because of the issue of cracking.Indirect 3D printing has been designed and drawn attention because of its high manufacturing speed and low cost.Indirect 3D printing separates the one-step forming process of direct 3D printing into binding and material sintering,avoiding the internal stress caused by rapid cooling,making it possible to realize the highquality ceramic component with complex shape.This paper presents the research progress of leading indirect 3D printing technologies,including binder jetting(BJ),stereolithography(SLA),and fused deposition modeling(FDM).At present,the additive manufacturing of ceramic materials is mainly achieved through indirect 3D printing technology,and these materials include silicon nitride,hydroxyapatite functional ceramics,silicon carbide structural ceramics.

Femtosecond-laser direct writing 3D micro/nano-lithography using VIS-light oscillator

Here we report a femtosecond laser direct writing(a precise 3D printing also known as two-photon polymerization lithography) of hybrid organic-inorganic SZ2080^(TM)pre-polymer without using any photo-initiator and applying ~100 fs oscillator operating at 517 nm wavelength and 76 MHz repetition rate. The proof of concept was experimentally demonstrated and benchmarking 3D woodpile nanostructures, micro-scaffolds, free-form micro-object “Benchy” and bulk micro-cubes are successfully produced. The essential novelty underlies the fact that non-amplified laser systems delivering just 40-500 p J individual pulses are sufficient for inducing localized cross-linking reactions within hundreds of nanometers in cross sections. And it is opposed to the prejudice that higher pulse energies and lower repetition rates of amplified lasers are necessary for structuring non-photosensitized polymers. The experimental work is of high importance for fundamental understanding of laser enabled nanoscale 3D additive manufacturing and widens technology’ s field of applications where the avoidance of photo-initiator is preferable or is even a necessity, such as micro-optics, nano-photonics, and biomedicine.

Sintering properties of in situ Ti-TiB microlattices created by 3D extrusion printing of TiH_(2)+TiB_(2) inks

A direct 3D extrusion printing technique was used to produce Ti-TiB filaments and microlattices.The sintering properties of 3D ink extrusion and sintering of in situ Ti-TiB composite structures made from TiH_(2)+TiB_(2) ink were investigated.The sintering kinetics of TiH2+TiB2 inks was studied during densification by pressureless sintering at 1050−1200℃ for 4−24 h in Ar.The linear shrinkage,grain size,microhardness,X-ray diffraction(XRD)patterns,and microstructural evolution of the Ti-TiB composite were studied.The sintering temperature had a more pronounced influence than the sintering time on the density of the Ti-TiB composite.There were two kinds of pores,irregular and spherical,caused by the Kirkendall effect and indiffusable gases.The TiB formed by in situ synthesis existed as either separated TiB whiskers(needle-like shapes)or clusters of TiB whiskers.The results of this work could be useful for controlling microporosity through incomplete sintering within filaments,especially for the production of in situ Ti-TiB with high volume fractions of TiB or other composites.

3D gel printing of VC reinforced high vanadium high-speed steel

Due to their high hardness and high strength,VC reinforced hard materials such as high vanadium high-speed steel(HVHSS)are not suitable for machining to obtain complex shape with low cost.Therefore,3D gel printing(3DGP)was employed to print HVHSS parts,using highly loaded slurry with 60%solid content as printing slurry.After printing parameters optimization,the printing sample had good surface quality,and obvious printing lines were observed.The extruded filament was in-situ cured,thus enough to maintain the designed shape.Uniform sintering shrinkage with a shrinkage rate of about 15%was obtained in the as-sintered sample with relative density of 99%.The surface roughness decreased from 6.5μm to 3.8μm.Fine carbides(<1μm)and dense microstructure were achieved.Besides,the as-sintered sample had comprehensive performance of HRC60 in hardness,3000 MPa in bend strength,and 20−26 J in impact energy.This study proposed one promising method to directly manufacture complex-shaped hard materials without subsequent machining.

Liu Zhongjun:3D Printing Reshapes Orthopedic Surgery

THERE is a 3D printing lab in the First Ward Zone of the Department of Orthopedics at Peking University Third Hospital（PUTH）.Although not big,it’s where Professor Liu Zhongjun,director of the department,spends most of his time,when not dealing with patients and students.

基于“双创”的高职《3D打印技术》课程评价模式与教学方法研究

该文围绕专业人才培养目标,结合专业知识能力和"双创"能力的培养需求,依据课程要求和教学内容,构建了融合"双创"、形式多样、主体多元的课程评价模式,探索了项目式教学、翻转课堂、以赛促学等相结合的课程教学方法体系。

《3D打印混凝土材料性能试验方法》、《3D打印混凝土基本力学性能试验方法》标准编制工作启动

协会标准《3D打印混凝土材料性能试验方法》、《3D打印混凝土基本力学性能试验方法》编制组成立暨第一次工作会议于2019年7月26日在西安市召开。中国混凝土与水泥制品协会、中国混凝土与水泥制品协会3D打印分会、河北工业大学、东南大学、尧柏水泥集团等单位的48位代表参加了会议。

Integrated 3D bioprinting-based geometry-control strategy for fabricating corneal substitutes

Background:The shortage of donor corneas is a severe global issue,and hence the development of corneal alternatives is imperative and urgent.Although attempts to produce artificial cornea substitutes by tissue engineering have made some positive progress,many problems remain that hamper their clinical application worldwide.For example,the curvature of tissue-engineered cornea substitutes cannot be designed to fit the bulbus oculi of patients.Objective:To overcome these limitations,in this paper,we present a novel integrated three-dimensional(3 D) bioprintingbased cornea substitute fabrication strategy to realize design,customized fabrication,and evaluation of multi-layer hollow structures with complicated surfaces.Methods:The key rationale for this method is to combine digital light processing(DLP) and extrusion bioprinting into an integrated 3 D cornea bioprinting system.A designable and personalized corneal substitute was designed based on mathematical modelling and a computer tomography scan of a natural cornea.The printed corneal substitute was evaluated based on biomechanical analysis,weight,structural integrity,and fit.Results:The results revealed that the fabrication of high water content and highly transparent curved films with geometric features designed according to the natural human cornea can be achieved using a rapid,simple,and low-cost manufacturing process with a high repetition rate and quality.Conclusions:This study demonstrated the feasibility of customized design,analysis,and fabrication of a corneal substitute.The programmability of this method opens up the possibility of producing substitutes for other cornea-like shell structures with different scale and geometry features,such as the glomerulus,atrium,and oophoron.

Coaxial 3D bioprinting of organ prototyps from nutrients delivery to vascularization

Vascular networks inside organs provide the means for metabolic exchange and adequate nutrition.Similarly,vascular or nutrient networks are needed when building tissue constructs>500μm in vitro due to the hydrogel compact pore size of bioinks.As the hydrogel used in bioinks is rather soft,it is a great challenge to reconstruct effective vascular networks.Recently,coaxial 3 D bioprinting was developed to print tissue constructs directly using hollow hydrogel fibers,which can be treated as built-in microchannels for nutrient delivery.Furthermore,vascular networks could be printed directly through coaxial 3 D bioprinting.This review summarizes recent advances in coaxial bioprinting for the fabrication of complex vascularized tissue constructs including methods,the effectiveness of varying strategies,and the use of sacrificial bioink.The limitations and challenges of coaxial 3 D bioprinting are also summarized.

Self-healing materials enable free-standing seamless large-scale 3D printing

Three-dimensional(3 D)printing has had a large impact on various fields,with fused deposition modeling(FDM)being the most versatile and cost-effective 3 D printing technology.However,FDM often requires sacrificial support structures,which significantly complicates the processing and increases the cost.Furthermore,poor layer-to-layer adhesion greatly affects the mechanical stability of 3D-printed objects.Here,we present a new Print-Healing strategy to address the aforementioned challenges.A polymer ink(Cu-DOU-CPU)with synergetic triple dynamic bonds was developed to have excellent printability and room-temperature self-healing ability.Objects with various shapes were printed using a simple compact 3D printer,and readily assembled into large sophisticated architectures via self-healing.Triple dynamic bonds induce strong binding between layers.Additionally,damaged printed objects can spontaneously heal,which significantly elongates their service life.This work paves a simple and powerful way to solve the key bottlenecks in FDM 3D printing,and will have diverse applications.

State-of-the-art of 3D printing technology of cementitious material—An emerging technique for construction

In recent few years, significant improvement has been made in developing largescale 3 D printer to accommodate the need of industrial-scale 3 D printing. Cementitious materials that are compatible with 3 D printing promote rapid application of this innovative technique in the construction field with advantages of cost effective, high efficiency, design flexibility and environmental friendly. This paper firstly reviews existing 3 D printing techniques that are currently being used in commercial3 D printers. It then summarizes three latest development of largescale 3 D printing systems and identifies their relationships and limiting factors. Thereafter, critical factors that are used to evaluate the workability and printable performance of cementitious materials are specified. Easy-extrusive, easy-flowing, well-buildable, and proper setting time are significant for cementitious material to meet the critical requirements of a freeform construction process. Finally, main advantages, potential applications and the prospects of future research of 3 D printing in construction technology are suggested. The objective of this work is to review current design methodologies and operational constraints of largescale 3 D printing system and provide references for optimizing the performance of cementitious material and promote its responsible use with largescale 3 D printing technology.

Fused deposition modeling 3D printed oral famotidine pulsatile release tablets

The aim of this study was to prepare pulsatile release tablets which provide different drug delayed-release time and realize personalized administration according to the needs of patients.Fused deposition modeling(FDM)3D printing technology was introduced into the field of pharmaceutics in this study,and the feasibility to prepare core-shell pulsatile release tablets was explored by combing 3D printing technology with the traditional manufacturing technology.The core of the pulsatile tablets was a commercial tablet obtained from the traditional technology,and the drug-free shell was prepared by the FDM 3D printing technology.Three kinds of tablet shells were designed using different parameters.Furthermore,the morphology,size,weight,hardness,and in vitro drug release of the 3D printed famotidine pusatile tablets were characterized and evaluated.The results showed that the 3D printed tablets appeared intact without any defects.Different parameters of outer shell affected the size,weight,hardness,and in vitro drug release of the tablets.The tablets achieved a personalized delayed release time varying from 5 to 7 h in vitro.In this way,a new method for preparing pulsatile release tablets and a new way for the personalized administration of pulsatile tablets were explored in this study.

Compatible hybrid 3D printing of metal and nonmetal inks for direct manufacture of end functional devices

The currently available 3D printing still cannot simultaneously deal with the metal and nonmetal inks together due to their huge difference in the melting points and poor compatible printability between each other. Here through introducing the low melting point alloy Bi35In48.6Sn16Zno.4 and silicone rubber as functional inks, we proposed a compatible hybrid 3D printing method for manufacturing the desired device, the supporting substrate and the allied package structure together. The principle of pneumatic-typed 3D printing of multiple inks was described and typical physical properties of the ink Bi35In48.6Sn16Zno.4 were measured. Several key factors dominating the printing quality such as the temperature of the printing head, the air pressure exerted upon the liquid metal ink in the syringe, the moving velocity and the height of the printing head etc. were clarified. A general way of directly printing out 3D structured electronic devices consisting of both metal and nonmetal materials was demonstrated. Such hybrid objects were patterned and formed up layer by layer with Bi35In48.6Sn16Zno.4 alloy and silicone rub- ber which would become solidified after standing for a period of time under room temperature. To illustrate the compatible printability of these printing inks, a three-layer tricolor LED stereo circuit with controlled lighting capability was further man- ufactured and evaluated. The present study opens an important hybrid 3D printing way for directly manufacturing functional and structural end devices in an easy and low cost way.