3D Printing of Tough Hydrogel Scaffolds with Functional Surface Structures for Tissue Regeneration

Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties.Inspired by Chinese ramen,we propose a universal fabricating method(printing-P,training-T,cross-linking-C,PTC&PCT)for tough hydrogel scaffolds to fill this gap.First,3D printing fabricates a hydrogel scaffold with desired structures(P).Then,the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance(T).Finally,the training results are fixed by photo-cross-linking processing(C).The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa(622-fold untreated)and have excellent biocompatibility.Furthermore,this scaffold possesses functional surface structures from nanometer to micron to millimeter,which can efficiently induce directional cell growth.Interestingly,this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt,and many hydrogels,such as gelatin and silk,could be improved with PTC or PCT strategies.Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers,blood vessels,and nerves within 4 weeks,prompting the rapid regeneration of large-volume muscle loss injuries.

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.

Three-dimensional printing technique assisted cognitive fusion in targeted prostate biopsy

Objective:To explore the effect of 3-dimensional(3D)printing-assisted cognitive fusion on improvement of the positive rate in prostate biopsy.Methods:From August to December 2014,16 patients with suspected prostatic lesions detected by multiparametric magnetic resonance imaging(MRI)were included.Targeted prostate biopsy was performed with the use of prostate 3D reconstruction modeling,computersimulated biopsy,3D printing,and cognitive fusion biopsy.All patients had received 3.0 T multiparametric MRI before biopsy.The DICOM MRI files were imported to medical imaging processing software for 3D reconstruction modeling to generate a printable.stl file for 3D printing with use of transparent resin as raw material.We further performed a targeted 2-to 3-core biopsy at suspected lesions spotted on MRI.Results:For the 16 patients in the present study,3D modeling with cognitive fusion-based targeted biopsy was successfully performed.For a single patient,1e2 lesions(average:1.1 lesions)were discovered,followed by 2-6 cores(average:2.4 cores)added as targeted biopsy.Systematic biopsies accounted for 192 cores in total,with a positive rate of 22.4%;targeted biopsies accounted for 39 cores in total,with a positive rate of 46.2%.Among these cases,10 patients(62.5%)were diagnosed with prostate adenocarcinoma,in which seven were discovered by both systematic and targeted biopsy,one was diagnosed by systematic biopsy only,and two were diagnosed by targeted biopsy only.For systematic biopsy,Gleason score ranged from 6 to 8(average:7),while that for targeted biopsy ranged from 6 to 9(average:7.67).Among the seven patients that were diagnosed by both systematic and targeted biopsy,three(42.8%)were reported with a higher Gleason score in targeted therapy than in systematic biopsy.Conclusion:3D printing-assisted cognitive fusion technique markedly promoted positive rate in prostate biopsy,and reduced missed detection in high-risk prostate cancer.

Treatment of Stanford type A aortic dissection with triple prefenestration, reduced diameter, and three-dimensional-printing techniques: A case report

BACKGROUND A 63-year-old female was diagnosed with acute Stanford type A aortic dissection.The patient had pain in the chest and back for 1 wk.The computed tomography angiography(CTA)showed Stanford type A aortic dissection(Myla type III aortic arch).The intimal tear was located at the top of the aortic arch and retrograded to the ascending aorta.CASE SUMMARY Preoperatively,a three-dimensional(3D)-printed model of the aortic arch was made according to CTA data.Then,under the guidance of the 3D-printed aortic model,a pre-fenestrated stent-graft was customized,and the diameter of the stent-graft was reduced intraoperatively by surgeons.3D printing,triple prefenestration,and reduced diameter techniques were used during the surgery.The CTA examinations were performed at the 3rd mo and 1st year after the surgery;the results showed that the aortic dissection was repaired without endoleak,and all three branches of the aortic arch remained unobstructed.CONCLUSION Applying the triple pre-fenestration technique for aortic arch lesions was feasible and minimally invasive in our case.The technique provides a new avenue for thoracic endovascular aortic repair of Stanford type A aortic dissection.

The Application and Operation-Effect Analysis for Complex Tibial Plateau Fractures with 3D Printing Technique

Objective: To investigate the value of 3D printing techniques in the treatment of complex tibial plateau fractures. Methods: From September 2016 to September 2018, 28 patients with complex tibial plateau fractures were treated in our hospital. According to the odevity of hospitalized order, the patients were divided into two groups. Group A used 3D reconstruction, virtually reduction, 3D printing and demonstration of individual fracture model before operation while group B only received conventional process by use X-rays or CT image. Comparison between the two groups was made in operation time, operative blood loss, radiation frequency, surgery instrument cost and knee function score. Results: The follow-up was 14.4 months on average (ranged 6 to 22 months). There was no statistical difference of the surgery instrument cost between the 2 groups (P > 0.05). The operation time of group A was significantly shorter than that of group B (P χ2 = 0.373, P = 0.54). Conclusion: 3D printing techniques can improve surgery effect in complex tibial plateau fractures.

Preoperative evaluation of transcatheter aortic valve replacement with assistance of 3D printing technique:Reanalysis of 4 death cases

Introduction:Transcatheter aortic valve replacement(TAVR)can have some fatal complications during and after the operation.Until recently,pre-procedural imaging with cardiac computed tomography(CT),which is required to evaluate for TAVR,had its own imperfections.We aimed to determine whether 3 D printed models can predict complications when other pre-procedural imaging techniques failed.Methods:Vascular center patients with aortic valve stenosis,who died after TAVR between June 2011 and June2016,were enrolled in this retrospective study.The CT datasets of the patients were imported into a threedimensional(3 D)construction software and then printed by flexible material.To predict complications during and after operations,we designed a release test using the non-valved stent mode that was consistent with the Edwards Sapien XT valve in size and radial support force.Result:The 3 D model predicted the coronary obstruction and annular rupture in the in vitro release process,which was consistent with what happened in the actual operation.Conclusion:Three-dimensional modeling facilitates pre-operative assessment of patients receiving TAVR,with accurate simulation of intraoperative status.

Application of 3D printing technique in pedicle screw placement for the lumbar isthmic spondylolisthesis

Objective:To investigate the application value of 3D printing technique in the operation of the lumbar isthmic spondylolisthesis.Methods Totally 48 patients with lumbar isthmic spondylolisthesis treated in our department from January 2015 to April 2017 were selected in the research plan.According to the random digital table method,they were divided into the observation group and the control group,with 25 cases in the observation group and 23 cases in control group.All patients were treated with transforaminal lumbar interbody fusion(TLIF).The control group made the observation group made the operation plan with 3D printing technology,and the operation plan according to the 3D CT reconstruction image.The clinical and imaging results were compared between the two groups、including operation time、intraoperative blood loss and X-ray exposure、complications、preoperative and postoperative ODI and JOA score.Results The accuracy of the screw placement in the observation group was 95.33%,which was significantly higher than those of 84.06%in the control group,the differences were statistically significant(P<0.05).Operation time and X-ray exposure and intraoperative blood loss in observation group were less than those in the control group,the differences were statistically significant(P<0.05).There were no significant differences spondylolisthesis reduction degree、ODI and JOA scores at postoperative different point between groups(P>0.05).Conclusions 3D printing technology is helpful to the development of the lumbar isthmic spondylolisthesis surgical plan,with the advantages of shortening the operation time and X-ray exposure,reducing the blood loss,improving the accuracy of the screw placement.

3D printing encouraging desired in-situ polypyrrole seed-polymerization for ultra-high energy density supercapacitors

The tireless pursuit of supercapacitors with high energy density entails the parallel advancement of wellsuited electrode materials and elaborately engineered architectures.Polypyrrole(PPy)emerges as an exceedingly conductive polymer and a prospective pseudocapacitive materials for supercapacitors,yet the inferior cyclic stability and unpredictable polymerization patterns severely impede its real-world applicability.Here,for the first time,an innovative seed-induced in-situ polymerization assisted 3D printing strategy is proposed to fabricate PPy-reduced graphene oxide/poly(vinylidene difluoride-cohexafluoropropylene)(PVDF-HFP)(PPy-rGO/PH)electrodes with controllable polymerization behavior and exceptional areal mass loading.The preferred active sites uniformly pre-planted on the 3D-printed graphene substrates serve as reliable seeds to induce efficient polypyrrole deposition,achieving an impressive mass loading of 185.6 mg cm^(-2)(particularly 79.2 mg cm^(-2)for polypyrrole)and a superior areal capacitance of 25.2 F cm^(-2)at 2 mA cm^(-2)for a 12-layer electrode.In agreement with theses appealing features,an unprecedented areal energy density of 1.47 mW h cm^(-2)for a symmetrical device is registered,a rarely achieved value for other PPy/rGO-based supercapacitors.This work highlights a promising route to preparing high energy density energy storage modules for real-world applications.

Biomimetic 3D printing of composite structures with decreased cracking

The development of tissue engineering and regeneration research has created new platforms for bone transplantation.However,the preparation of scaffolds with good fiber integrity is challenging,because scaffolds prepared by traditional printing methods are prone to fiber cracking during solvent evaporation.Human skin has an excellent natural heat-management system,which helps to maintain a constant body temperature through perspiration or blood-vessel constriction.In this work,an electrohydrodynamic-jet 3D-printing method inspired by the thermal-management system of skin was developed.In this system,the evaporation of solvent in the printed fibers can be adjusted using the temperature-change rate of the substrate to prepare 3D structures with good structural integrity.To investigate the solvent evaporation and the interlayer bonding of the fibers,finite-element analysis simulations of a three-layer microscale structure were carried out.The results show that the solvent-evaporation path is from bottom to top,and the strain in the printed structure becomes smaller with a smaller temperaturechange rate.Experimental results verified the accuracy of these simulation results,and a variety of complex 3D structures with high aspect ratios were printed.Microscale cracks were reduced to the nanoscale by adjusting the temperature-change rate from 2.5 to 0.5℃s-1.Optimized process parameters were selected to prepare a tissue engineering scaffold with high integrity.It was confirmed that this printed scaffold had good biocompatibility and could be used for bone-tissue regeneration.This simple and flexible 3D-printing method can also help with the preparation of a wide range of micro-and nanostructured sensors and actuators.

Investigation on mechanical properties regulation of rock-like specimens based on 3D printing and similarity quantification

3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechanical properties of 3D-printed specimens to make them proportionally similar to natural rocks.This study investigates mechanical properties of 3D-printed rock analogues prepared by furan resin-bonded silica sand particles.The mechanical property regulation of 3D-printed specimens is realized through quantifying its similarity to sandstone,so that analogous deformation characteristics and failure mode are acquired.Considering similarity conversion,uniaxial compressive strength,cohesion and stress–strain relationship curve of 3D-printed specimen are similar to those of sandstone.In the study ranges,the strength of 3D-printed specimen is positively correlated with the additive content,negatively correlated with the sand particle size,and first increases then decreases with the increase of curing temperature.The regulation scheme with optimal similarity quantification index,that is the sand type of 70/140,additive content of 2.5‰and curing temperature of 81.6℃,is determined for preparing 3D-printed sandstone analogues and models.The effectiveness of mechanical property regulation is proved through uniaxial compression contrast tests.This study provides a reference for preparing rock-like specimens and engineering models using 3D printing technology.

Light-based 3D printing of stimulus-responsive hydrogels forminiature devices:recent progress and perspective

Miniature devices comprising stimulus-responsive hydrogels with high environmental adaptability are now considered competitive candidates in the fields of biomedicine,precise sensors,and tunable optics.Reliable and advanced fabricationmethods are critical formaximizing the application capabilities ofminiature devices.Light-based three-dimensional(3D)printing technology offers the advantages of a wide range of applicable materials,high processing accuracy,and strong 3D fabrication capability,which is suitable for the development of miniature devices with various functions.This paper summarizes and highlights the recent advances in light-based 3D-printed miniaturized devices,with a focus on the latest breakthroughs in lightbased fabrication technologies,smart stimulus-responsive hydrogels,and tunable miniature devices for the fields of miniature cargo manipulation,targeted drug and cell delivery,active scaffolds,environmental sensing,and optical imaging.Finally,the challenges in the transition of tunable miniaturized devices from the laboratory to practical engineering applications are presented.Future opportunities that will promote the development of tunable microdevices are elaborated,contributing to their improved understanding of these miniature devices and further realizing their practical applications in various fields.

Digital light processing based multimaterial 3D printing:challenges,solutions and perspectives

Multimaterial(MM)3D printing shows great potential for application in metamaterials,flexible electronics,biomedical devices and robots,since it can seamlessly integrate distinctive materials into one printed structure.Among numerous MM 3D printing technologies,digital light processing(DLP)MM 3D printing is compatible with a wide range of materials from hydrogels to ceramics,and can print MM 3D structures with high resolution,high complexity and fast speed.This paper introduces the fundamental mechanisms of DLP 3D printing,and reviews the recent advances of DLP MM 3D printing technologies with emphasis on material switching methods and material contamination issues.It also summarizes a number of typical examples of DLP MM 3D printing systems developed in the past decade,and introduces their system structures,working principles,material switching methods,residual resin removal methods,printing steps,as well as the representative structures and applications.Finally,we provide perspectives on the directions of the further development of DLP MM 3D printing technology.

Polar-coordinate line-projection light-curing continuous 3D printing for tubular structures

3D printing techniques offer an effective method in fabricating complex radially multi-material structures.However,it is challenging for complex and delicate radially multi-material model geometries without supporting structures,such as tissue vessels and tubular graft,among others.In this work,we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform.The 3D model fabrication is accomplished through line projection.The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume.By controlling the distance between the rod and the printing window,we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers.By controlling the width of fine slits at the printing window,we achieved the printing of structures with a minimum feature size of 10 micrometers.Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s.Additionally,it enables the printing of axial multi-material structures,thereby achieving adjustable mechanical strength.This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry,aerospace,and more.

Extrusion 3D printing of carbon nanotube-assembled carbon aerogel nanocomposites with high electrical conductivity

Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels.However,there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric features.Herein,a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon(CNT/C)aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks,in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer microgels.After extrusion printing,the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic geometries.Benefiting from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases,3D-printed CNT/C aerogels exhibit enhanced mechanical strength(fracture strength,0.79 MPa)and typical porous structure characteristics,including low density(0.220 g cm^(-3)),high surface area(298.4 m^(2)g^(-1)),and concentrated pore diameter distribution(~32.8nm).More importantly,CNT nanofibers provide an efficient electron transport pathway,imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 S cm^(-1).Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.

Electrospinning/3D printing-integrated porous scaffold guides oral tissue regeneration in beagles

The combined use of guided tissue/bone regeneration(GTR/GBR)membranes and bone filling grafts represents a classical therapy for guiding the regeneration and functional reconstruction of oral soft and hard tissues.Nevertheless,due to its displacement and poor mechanical support,bone meal is not suitable for implantation in the case of insufficient cortical bone support and large dimensional defects.The combination of GTR/GBR membrane with a three-dimensional(3D)porous scaffold may offer a resolution for the repair and functional reconstruction of large soft and hard tissue defects.In this study,a novel integrated gradient biodegradable porous scaffold was prepared by bonding a poly(lactic-co-glycolic acid)(PLGA)/fish collagen(FC)electrospun membrane(PFC)to a 3D-printed PLGA/nano-hydroxyapatite(HA)(PHA)scaffold.The consistency of the composition(PLGA)ensured strong interfacial bonding between the upper fibrous membrane and the lower 3D scaffold.In vitro cell experiments showed that the PFC membrane(upper layer)effectively prevented the unwanted migration of L929 cells.Further in vivo investigations with an oral soft and hard tissue defect model in beagles revealed that the integrated scaffold effectively guided the regeneration of defective oral tissues.These results suggest that the designed integrated scaffold has great potential for guiding the regeneration and reconstruction of large oral soft and hard tissues.

3D printing of poly(ethyleneimine)-functionalized Mg-Al mixed metal oxide monoliths for direct air capture of CO_(2)

Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from the air,lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies.A structured adsorbent is essential for the implementation of gas-solid contactors for cost-and energy-efficient DAC systems.In this study,efficient adsorbent poly(ethyleneimine)(PEI)-functionalized Mg-Al-CO_(3)layered double hydroxide(LDH)-derived mixed metal oxides(MMOs)are three-dimensional(3D)printed into monoliths for the first time with more than 90%adsorbent loadings.The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths.This structure exhibits a 32.7%higher specific surface area and a 46.1%higher pore volume,as compared to the direct printing of the MMO powder into a monolith.After impregnation of PEI,the monolith demonstrates a large adsorption capacity(1.82 mmol/g)and fast kinetics(0.7 mmol/g/h)using a CO_(2)feed gas at 400 ppm at 25℃,one of the highest values among the shaped DAC adsorbents.Smearing of the amino-polymers during the post-printing process affects the diffusion of CO_(2),resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths.The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.

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 printing in space:from mechanical structures to living tissues

3D printing stands at the forefront of transforming space exploration,offering unprecedented on-demand and rapid manufacturing capabilities.It adeptly addresses challenges such as mass reduction,intricate component fabrication,and resource constraints.Despite the obstacles posed by microgravity and extreme environments,continual advancements underscore the pivotal role of 3D printing in aerospace science.Beyond its primary function of producing space structures,3D printing contributes significantly to progress in electronics,biomedicine,and resource optimization.This perspective delves into the technological advantages,environmental challenges,development status,and opportunities of 3D printing in space.Envisioning its crucial impact,we anticipate that 3D printing will unlock innovative solutions,reshape manufacturing practices,and foster self-sufficiency in future space endeavors.

3D Printing of Periodic Porous Metamaterials for Tunable Electromagnetic Shielding Across Broad Frequencies

The new-generation electronic components require a balance between electromagnetic interference shielding efficiency and open structure factors such as ventilation and heat dissipation.In addition,realizing the tunable shielding of porous shields over a wide range of wavelengths is even more challenging.In this study,the well-prepared thermoplastic polyurethane/carbon nanotubes composites were used to fabricate the novel periodic porous flexible metamaterials using fused deposition modeling 3D printing.Particularly,the investigation focuses on optimization of pore geometry,size,dislocation configuration and material thickness,thus establishing a clear correlation between structural parameters and shielding property.Both experimental and simulation results have validated the superior shielding performance of hexagon derived honeycomb structure over other designs,and proposed the failure shielding size(D_(f)≈λ/8-λ/5)and critical inclined angle(θf≈43°-48°),which could be used as new benchmarks for tunable electromagnetic shielding.In addition,the proper regulation of the material thickness could remarkably enhance the maximum shielding capability(85-95 dB)and absorption coefficient A(over 0.83).The final innovative design of the porous shielding box also exhibits good shielding effectiveness across a broad frequency range(over 2.4 GHz),opening up novel pathways for individualized and diversified shielding solutions.

Rapid fabrication of modular 3D paper-basedmicrofluidic chips using projection-based 3D printing

Paper-based microchips have different advantages,such as better biocompatibility,simple production,and easy handling,making them promising candidates for clinical diagnosis and other fields.This study describes amethod developed to fabricate modular three-dimensional(3D)paper-based microfluidic chips based on projection-based 3D printing(PBP)technology.A series of two-dimensional(2D)paper-based microfluidic modules was designed and fabricated.After evaluating the effect of exposure time on the accuracy of the flow channel,the resolution of this channel was experimentally analyzed.Furthermore,several 3D paper-based microfluidic chips were assembled based on the 2D ones using different methods,with good channel connectivity.Scaffold-based 2D and hydrogel-based 3D cell culture systems based on 3D paper-based microfluidic chips were verified to be feasible.Furthermore,by combining extrusion 3D bioprinting technology and the proposed 3D paper-based microfluidic chips,multiorgan microfluidic chips were established by directly printing 3D hydrogel structures on 3D paperbased microfluidic chips,confirming that the prepared modular 3D paper-based microfluidic chip is potentially applicable in various biomedical applications.