3D-printable Boron Nitride/Polyacrylic Hydrogel Composites with High Thermal Conductivities

Polyacrylic acid(PAA)hydrogel composites with different hexagonal boron nitride(h-BN)fillers were synthesized and successfully 3D-printed while their thermal conductivity was systematically studied.With the content of h-BN increasing from 0.1 wt%to 0.3 wt%,the thermal conductivity of the 3D-printed composites has been improved.Moreover,through the shear force given by the 3D printer,a complete thermal conductivity path is obtained inside the hydrogel,which significantly improves the thermal conductivity of the h-BN hydrogel composites.The maximum thermal conductivity is 0.8808 W/(m·K),leading to a thermal conductive enhancement of 1000%,compared with the thermal conductivity of pure PAA hydrogels.This study shows that using h-BN fillers can effectively and significantly improve the thermal conductivity of hydrogelbased materials while its 3D-printable ability has been maintained.

Modulation of the thermal transport of micro-structured materials from 3D printing

It is desirable to fabricate materials with adjustable physical properties that can be used in different industrial applications.Since the property of a material is highly dependent on its inner structure,the understanding of structure–property correlation is critical to the design of engineering materials.3D printing appears as a mature method to effectively produce micro-structured materials.In this work,we created different stainless-steel microstructures by adjusting the speed of 3D printing and studied the relationship between thermal property and printing speed.Our microstructure study demonstrates that highly porous structures appear at higher speeds,and there is a nearly linear relationship between porosity and printing speed.The thermal conductivity of samples fabricated by different printing speeds is characterized.Then,the correlation between porosity,thermal conductivity,and scanning speed is established.Based on this correlation,the thermal conductivity of a sample can be predicted from its printing speed.We fabricated a new sample at a different speed,and the thermal conductivity measurement agrees well with the value predicted from the correlation.To explore thermal transport physics,the effects of pore structure and temperature on the thermal performance of the printed block are also studied.Our work demonstrates that the combination of the 3D printing technique and the printing speed control can regulate the thermophysical properties of materials.

A facile method to fabricate cell-laden hydrogel microparticles of tunable sizes using thermal inkjet bioprinting

This study investigates the application of a drop-on-demand(DOD)thermal inkjet(TIJ)-based bioprinting system for the fabrication of cell-laden hydrogel microparticles(HMPs)with tunable sizes.The TIJ bioprinting technique involves the formation of vapor bubbles within the print chamber through thermal energy,expelling small droplets of bio-ink onto a substrate.The study employs a heat-treated saponified gelatin-based bio-ink,HSP-GelMA.This bio-ink is modified through methacrylic anhydride functionalization and undergoes subsequent saponification and heat treatment processes.Various concentrations of SPAN 80 surfactant in mineral oil were evaluated to assess their influence on HMP size and stability.The results indicate a direct correlation,with higher SPAN 80 concentrations resulting in smaller and more stable HMPs.The study further investigates the influence of jetting volume on HMP size distribution,revealing that larger jetting volumes lead to increased HMP sizes,attributed to droplet coalescence.This is supported by our further study via a Monte Carlo simulation,which shows that the mean droplet diameter grows approximately linear with the number of dispensed droplets.In addition,the study demonstrates the capability of the TIJ bioprinting system to achieve multimaterial encapsulation within HMPs,exemplified by staining living cells with distinct cytoplasmic membrane dyes.The presented approach provides insights into the controlled fabrication of cell-laden HMPs,highlighting the versatility of the TIJ bioprinting system for potential applications in tissue engineering and drug delivery.

A Dielectric Ink Combining Acrylate and Cyanate Moieties for Inkjet 3D Printing with Good Thermal Stability

Inkjet 3D printing has potential in the additive manufacturing of electronic circuits and devices.However,inks that can be used for printing layers with T5%>300℃ or hardness>200 MPa have been rarely reported.Cyanate ester(CE)polymers have excellent thermal stability,high strength,and low shrinkage compared to other common dielectric inks for inkjet 3D printing,but cannot be quickly shaped by ultraviolet(UV)irradiation or thermal treatment.Combining CEs with UV-curable monomers may be a possible way to accelerate crosslinking,but there are challenges from the adverse effects of the dilution of both monomers.In this study,dielectric inks with acrylate and cyanate moieties were developed.The low viscosity and surface tension of the CE precursor(Bisphenol E cyanate ester)were combined with photocurable acrylate diluent monomers and cross-linker to realize an ink suitable for inkjet 3D printing.An internal dual three-dimensional cross-linked network structure resin was prepared by a combination of photocuring and thermal curing with T5%up to 326.69℃,hardness up to 431.84 MPa,dielectric constant of 2.70 at 8 GHz,and shrinkage of 1.64%.The developed dielectric inks can be applied to the 3D printing of printed circuit boards and other electronic devices that require dielectric properties.

Numerical Analysis of Printed Circuit Board with Thermal Vias: Heat Transfer Characteristics under Nonisothermal Boundary Conditions

A thermal via has been used to enhance the heat transfer through the printed circuit board (PCB). Because the thermal conductivity of a dielectric material is very low, the array of metal vias is placed to make thermal paths in the PCB. This paper describes the numerical analysis of the PCB having metal vias and focuses on the heat transfer characteristics under the nonisothermal boundary conditions. The mathematical model of the PCB has the metal vias between two metal sheets. Under 2nd and 3rd kinds of boundary conditions, the temperature distribution is obtained numerically by changing the design parameters. The discussion is also made on the effective thermal conductivity of the PCB. In industry, the use of effective thermal conductivity is convenient for thermal engineers because it simplifies the calculation process, that is, the composite board can be modeled as a homogeneous medium. From the numerical results, it is confirmed that the placement of metal sheets and the population of metal vias are important factors to dominate the heat transfer characteristics of the PCB. It is also shown that although the nonisothermal boundary conditions are applied at the boundary surface, the temperature difference between the heated and the cooled section is almost uniform when the metal vias are populated densely with the metal sheets. In this case, the effective thermal conductivity of the PCB is found to be the same irrespective of the boundary conditions, that is, whether the isothermal or the nonisothermal boundary conditions are applied.

Compatibility and stability studies involving polymers used in fused deposition modeling 3D printing of medicines

One of the challenges in developing three-dimensional printed medicines is related to their stability due to the manufacturing conditions involving high temperatures.This work proposed a new protocol for preformulation studies simulating thermal processing and aging of the printed medicines,tested regarding their morphology and thermal,crystallographic,and spectroscopic profiles.Generally,despite the strong drug-polymer interactions observed,the chemical stability of the model drugs was preserved under such conditions.In fact,in the metoprolol and Soluplus®composition,the drug's solubilization in the polymer produced a delay in the drug decomposition,suggesting a protective effect of the matrix.Paracetamol and polyvinyl alcohol mixture,in turn,showed unmistakable signs of thermal instability and chemical decomposition,in addition to physical changes.In the presented context,establishing protocols that simulate processing and storage conditions may be decisive for obtaining stable pharmaceutical dosage forms using three-dimensional printing technology.

Research on Intelligent Control System of Thermal Print Head Based on Field Programmable Gate Array

Thermal print head heating real-time temperature fluctuations are too large,often causing damage to the print head heating point,resulting in poor print quality and unsatisfactory print results.Therefore,to improve the stability of the thermal print head during printing,and at the same time to solve the inefficiency of the traditional single-chip microcomputer control of the thermal print head heating method,a field programmable gate array-based thermal print head heating control method is proposed.To control the core,the intelligent fuzzy Proportional-Integral-Differential(PID)control algorithm is used to ensure that the temperature of the print head can be stabilized quickly.Through simulation and experimental verification,it is shown that the intelligent fuzzy PID control algorithm greatly improves the temperature stabilization effect,and the time required to reach stability short not only improve the printing accuracy but also extend the life of the print head.

数据驱动的中温隔热陶瓷管件结构优化设计及性能评估

随着中温区电加热的电子产品和家电用品不断涌现,低成本的高效保温隔热材料研究日益成为热点。如何确保管路内部快速升温并避免外表温度大幅波动,有效提高能源利用率,是保温隔热材料领域的挑战。据此,本研究以低熔点玻璃助烧结的镁橄榄石、莫来石、珍珠岩和磷酸锌等复合物陶瓷为对象,从数据驱动的壁内多孔结构隔热管件优化设计出发,开展陶瓷隔热管件三维打印制造,通过显微结构和力学性能分析,并围绕管件的导热、隔热影响因素评估,系统考察了该类新型隔热管件的理化、力学和隔热性能及影响关系。结果表明,通过对沿管壁环绕的矩形大孔高度调控(400~1 200μm)、管腔内热源区的管壁倍增(1.2 mm×2 mm)以及有机微球造孔剂引入(~9%),同时通过烧结温度控制(700~750℃),可以显著改善热流出口区的温度水平(~20℃),并显著优于不锈钢真空隔热管的出口温度。研究结果表明,增材制造复合陶瓷管件具有优良的综合性能以及较低的原料成本,使得多孔陶瓷隔热管件在中温隔热领域具有广阔的应用前景。

3D打印柔性SiO_(2)气凝胶复合材料的研究

SiO_(2)气凝胶因特殊网络结构而存在优异的性质,如高比表面积、高孔隙率、低热导率和低密度,是优异的保温绝热材料。但SiO2气凝胶机械性能脆弱,导致传统制造方法难以制备复杂和微小型构件,极大地阻碍了SiO_(2)气凝胶在隔热领域的发展和应用。本文通过3D打印直写技术制备了柔性SiO_(2)气凝胶复合材料,通过研究不同聚乙烯醇(PVA)溶液和十八酸钠(C_(17)H_(35)COONa)的含量,找到最佳浆料配比,打印的柔性SiO_(2)气凝胶复合材料在100℃下的热导率低至0.026 W/(m·K),同时具有较好的压缩性能、弯曲性能和疏水性。这项研究为SiO_(2)气凝胶的规模化应用提供一种可能。

基于热泡喷墨技术制备均匀细胞球的创新方法

细胞球在药物发现、生理病理学研究和组织工程等多个领域发挥重要作用。然而,传统的制造细胞球的方法限制了其应用。本文提出了一种基于热泡喷墨打印技术的系统性方法,称为聚集打印,它可以快速、高通量且低成本地产出均匀尺寸的球体。聚集打印可以在16 min内产出864个直径均匀的细胞球。本文以CHO细胞作为研究对象,仔细分析了打印后的细胞活性。同时,为了提高细胞球体尺寸的均匀性,提出3种优化方法,分别可以将细胞球体直径的变异系数(CV值)降低17.04%~48.38%不等,最后研究了打印后的细胞球培养0、1、4、7 d的生长情况。实验结果充分证明了聚集打印方法在细胞球体制造方面的优势性,本方法也为类器官的制备提供参考。

高温熔盐印刷电路板式换热器的热工水力特性研究

印刷电路板式换热器(Printed Circuit Heat Exchanger,PCHE)换热效率高,结构紧凑,可作为小型模块化熔盐堆热量传输的关键设备,对其流动换热特性的研究具有重要意义。采用数值模拟方法,以翼型通道的熔盐(FNaBe)-氦气换热器为研究对象,通过计算流体动力学(Computational Fluid Dynamics,CFD)数值模拟计算对其熔盐侧的传热特性和阻力特性进行对比分析,分别得到不同温度、翅片类型和不同节距结构下的熔盐(FNaBe)-氦气换热器的流动换热特性,并与传统直通道结构对比进行综合评估。研究结果表明,数值模拟的计算结果与实验结果对比符合较好,翼型翅片流道结构相较于直通道结构能够强化传热、降低阻力,其中节距为8 mm的NACA0025翼型翅片流道结构的流动传热特性最好。本研究建立的数值模拟方法能够用于印刷电路板式换热器的流动传热特性的预测,拟合出节距为8 mm的NACA0025翼型翅片结构的经验关联式,为后续换热器的设计提供理论基础。

直写型3D打印制备SiOC基气凝胶及其隔热性能研究

以甲基三甲氧基硅烷与乙烯基三乙氧基硅烷为原料,添加SiO_(2)气凝胶粉体,共同水解混合制备SiOC溶胶浆料,采用直写型3D打印和常压干燥制备SiOC基气凝胶,对其微观形貌、隔热及力学性能进行了探究。结果表明,该材料具有较低密度及收缩率,热导率为0.03665W/(m·K)。采用TEOS溶胶-凝胶法对其填充修饰后,热导率有效降低至0.017W/(m·K),抗压强度提高至1.87MPa。TEOS填充形成的SiO_(2)气凝胶填充了3D打印SiOC基气凝胶的宏观孔洞和内部的微米孔结构,有效降低了气相传热途径,从而提高了隔热性能。

Thermal shock resistant 3D printed ceramics reinforced with MgAl_(2)O_(4) shell structure

The demand for the swirl nozzle with enhanced temperature resistance and lightweight properties is in-creasing as the thrust-to-weight ratio of aero-engines rises.The Al_(2)O_(3) ceramic swirl nozzle can maintain high strength in a hostile environment of high temperature and severe corrosion,while also meeting the requirements of aircraft to enhance efficiency and decrease weight.However,Al_(2)O_(3) ceramics are limited in their application for aerospace components due to their poor thermal shock resistance(TSR)stemming from their inherent brittleness.This work reported an innovative design and fabrication strategy based on photopolymerization 3D printing technology to realize the three-dimensional shell structure through element interdiffusion and nanoscale stacking of the reinforced phase.With this strategy,a novel type of the new dual-structure Al_(2)O_(3) ceramic composed of MgAl_(2)O_(4) shell structure and matrix could be con-structed in situ.The nano-sized MgAl_(2)O_(4) caused a crack passivation effect after the thermal shock,which could improve the strength and TSR of 3D-printed Al_(2)O_(3) ceramic.In addition,the effects of MgO content and sintering temperature on sintering behavior,flexural strength,porosity,and TSR of Al_(2)O_(3) ceram-ics manufactured by digital light processing(DLP)processing were systematically studied.The optimum overall performance of Al_(2)O_(3) ceramics was obtained at the sintering temperature of 1550℃and the MgO content of 1.0 wt.%,with a maximum flexural strength of 111.929 MPa and a critical temperature difference of 374.24℃for TSR.Based on the above research,an aero-engine swirl nozzle with high ther-mal shock resistance has been successfully prepared by ceramic 3D printing technology,which enhances high-temperature resistance and promotes lightweight design in aero-engine.

3D打印隔热材料研究进展

3D打印技术能够实现面向性能的设计以及非常规结构的制造,其在隔热领域的应用可以使材料具有更加精细、可控、定制化的结构与功能。当前,3D打印隔热材料技术仍处于快速迭代期,打印材料、结构设计和制造工艺等技术瓶颈尚待突破。本文对3D打印隔热材料的现状进行了综述,简要分析了在隔热材料制造方面较有前景的3D打印工艺,对比了各工艺的优缺点以及适用的材料类型,着重讨论了3D打印陶瓷、发泡混凝土、泡沫塑料和气凝胶材料在隔热领域的研究进展,最后总结了目前面临的技术挑战和未来的主要发展方向。

3D打印聚乳酸的改性研究与应用进展

聚乳酸(PLA)是一种生物可降解热塑性聚酯,是极有前景的生物基可降解材料之一。PLA具有优异的力学性能、良好的可塑性及生物相容性,是理想的3D打印材料。3D打印PLA材料在多个领域尤其是医用方面有巨大的潜力。然而,PLA固有的脆性和较差的耐热、耐水解性限制了它的应用范围。近年来,学者对3D打印PLA的改性进行了大量研究。本文归纳了3D打印PLA的研究进展,分别从共混改性、复合改性、立构复合、涂层法和化学改性这几方面讨论了提高材料性能的原理与方法,并对相关性能进行了分析对比。共混法虽然简单易操作,但不利于材料的均匀化,且有时改性效果不够明显。复合改性向PLA中加入碳基添加剂、金属添加剂、植物纤维等填料,改性同时可赋予3D打印PLA更多功能,但易出现界面不相容等问题。此外,还有立构复合、涂层法、化学改性等新方法具有重要的研究价值。在此基础上,结合目前3D打印PLA在实际应用中的发展情况,分析了3D打印PLA仍存在的问题,对3D打印PLA未来的研究方向进行了展望。

淀粉基凝胶在食品3D打印中的研究进展

食品3D打印技术是一种在食品领域新兴的、由计算机辅助软件控制的智能化快速成型技术。因其具有高效、便捷、个性化定制的特点,在食品加工领域中有较大的发展潜力。淀粉作为一种可再生的天然高分子,具有无毒害、经济环保、资源丰富的优点,是3D打印优质的食品级油墨。近年来,随着食品3D打印技术的不断发展,如何提高天然食用凝胶的可打印性成为研究热点。为更好地了解淀粉基凝胶3D打印的研究进展,该文从3D打印技术原理、淀粉基原料3D打印特性、影响淀粉基凝胶3D打印效果的因素、淀粉基凝胶3D打印的应用现状以及面临的挑战等方面进行综述,以期为淀粉基凝胶在食品3D打印中的发展和应用提供参考。

基于微流道冷却的水卡式量热计结构优化与试验分析

高声速飞行器再入过程中面临严峻的气动加热环境,最高气流温度可达上万摄氏度,常用量热计在如此高的气流温度下,缺乏良好的热流测试性能和热负荷生存能力。为解决地面试验中高超声速飞行器模型表面高热流的连续、精准测量难题,研发了一种基于微流道冷却的新型水卡式量热计,其内部微型流道结构采用3D打印技术构建。通过数值仿真,确定了新型水卡式量热计的微流道尺寸与布局,与同一冷壁热流的传统水卡式量热计相比,其核心区域温升降低近50%,验证了微流道水卡式量热计在极端热环境下的测试能力和生存能力。电弧加热射流试验结果表明:微流道水卡式量热计可以同步测量压力、温度、热流数据,实现了高温流场参数的集成化辨识,并具有良好动态响应特性;最大热流测量值超过18 MW/m^(2),测量绝对偏差和平均偏差分别控制在3.44%与±1.72%以内。

丙烯酸酯型端羟基聚醚双固化黏合剂的合成及打印成型固化机理

以聚四氢呋喃醚二醇(PTHF)和3-甲基-3-丙烯酰氧甲基氧杂环丁烷(MMO)为原料,通过阳离子开环聚合反应机理,设计、合成了丙烯酸酯型端羟基聚醚黏合剂(MAPTHF),再与六亚甲基二异氰酸酯缩二脲固化剂(N-100)、2,4,6-三甲基苯甲酰基二苯基氧化膦(TPO)和1,4-丁二醇(BDO)组成光-热双固化黏合体系,通过光固化、热固化双步骤获得了光-热双固化弹性体。采用FTIR、NMR和GPC表征了MAPTHF的结构组成和物性参数,探究了光-热双固化黏合体系最佳的固化工艺参数和较优的物料配比,考察了光-热双固化弹性体的力学性能和热稳定性。结果表明,MAPTHF光-热双固化黏合体系可在紫外光照(5 W,395 nm)下5 s快速固化,在加热(65℃)3.0 h内实现完全固化,具有快速固化成形和短时间内完全固化特征;光-热双固化弹性体的拉伸强度为3.15 MPa,断裂伸长率为350%。该光-热双固化黏合体系用于3D打印复合推进剂,得到了较优异的打印成型效果。

石墨烯基水性导电油墨的制备及其在低温热管理中的应用

【目的】为了制备环保型的石墨烯基水性导电油墨,印刷高性能柔性电阻加热器(flexible resistive heaters,FRHs),实现锂离子电池的低温热管理。【方法】采用球磨法制备石墨烯基水性导电油墨;采用扫描电子显微镜和透射电子显微镜表征石墨烯及印刷图案的形貌和结构;采用平板流变仪和四探针电阻仪表征炭黑含量对石墨烯基水性油墨流变性能和印刷图案导电性能的影响;探讨石墨烯基FRHs的响应速率、热稳定性和力学性能,以及其在锂离子电池低温热管理中的应用。【结果】油墨的静态黏度和黏度恢复率随着炭黑含量的增加而增大,印刷图案的电导率在炭黑质量分数为15%时达到最大,为20383 S/m;石墨烯基FRHs在8 V的低电压下30 s快速达到150℃,能够实现120次的重复开关循环,在72 h的持久运行后温度仅增加2.54%,并且在2000次的弯折后温度变化小于2.1%。在电压为6 V时将锂离子电池从-30℃预热至20℃,并在30 min内实现80%的充电容量。【结论】射流空化法产生的高剥离度、完好晶体结构和较大横向尺寸(1μm)的石墨烯与填充于其中的炭黑使油墨具有合适的流变性,并在印刷图案中构建致密的导电通道,赋予FRHs优异的性能。

热转印系统色带传动过程张力分析与建模

为保证热转印过程中薄膜色带传动稳定进而实现高质量转印,建立正确的热转印色带传动张力模型十分关键。首先,研究了热转印色带传动系统组成及转印原理,并根据色带传动路径分辊间段、放卷段和收卷段3阶段对色带传动系统张力进行了建模与分析。然后,结合热转印色带卷材的黏弹性分析张力形成机制,改进了卷绕系统经典张力公式,建立了辊间段薄膜色带张力模型。针对传动系统的放卷区域,分析了摩擦对薄膜色带传动张力的影响,提出张力下降系数以评估张力损失。考虑色带张力非线性时变的特点,利用步进电动机负载模型求解收卷区域色带张力。最后,通过对比仿真与实验所得的色带张力变化曲线,验证了模型的准确性,为后续张力控制方案设计奠定了基础。