In this edition of CraAMed, we see how researchers are reviewing, and improving 3D printing processes including 4D printing and 3D bioprinting. New applications are also explored, leading down new avenues in drug screening, and important discoveries from beneath the ocean.
The challenges of 4D printing, and microfluidic LEGO
University of California, Berkeleyresearchers have published a review of 4D printing, which characterizes various smart materials and their applications in the fields of medicine,软机器人技术，，，，and self-construction structures. The review also discusses the future of 4D printing and current challenges against the progression of technology, including “the limitations of current 3D printers to address fundamental 3D printing issues” such as support-free structures.
“Developments in 4D-printing: a review on current smart materials, technologies, and applications“是published in the国际智能和纳米材料杂志。
在Brown University，，，，Rhode Island, researchers have devised a way to 3D print self-adhesive hydrogels. In a study titled, “3D printed self-adhesive PEGDA–PAA hydrogels as modular components for soft actuators and microfluidics“研究人员设计了一组对外部刺激并改变形状的模块化水凝胶。为研究开发了一个自动施加的软抓手和一个像乐高的水凝胶构建块。
Thomas M. Valentin, a biomedical engineer and co-author of the paper, explained, “The modular LEGO blocks are interesting in that we could create a prefabricated toolbox for microfluidic devices.” Valentin goes on, “You keep a variety of preset parts with different microfluidic architectures on hand, and then you just grab the ones you need to make your custom microfluidic circuit. Then you heal them together and it’s ready to go.”
Furthermore, Ian Y. Won, assistant professor of engineering and co-author of the paper, said, “There’s a lot of interest in materials that can change their shapes and automatically adapt to different environments,”
“So here we demonstrate a material the can flex and reconfigure itself in response to an external stimulus.”
Optimization液滴的需求和FFF技术
In a roll-to-roll process of manufacturing electronics, defects such as bridging and hollowing can occur. To counter such problems researchers atSandia National Laboratories和University of New Mexicohas 3D printed metamaterials and porous stamps for ink deposition. This prevents excess amount of ink from being deposited.
“Architected Porous Media Designed for Flexographic Printing” won Best Poster at the Materials Research Society (MRS) Fall 2018 meeting.
Using the multi-objective optimization technique, researchers from the新加坡国立大学and东北大学，，，，attempted to optimize Drop-on-demand (DOD) bioprinting. According to the paper, “Multi-Objective Optimization Design through Machine Learning for Drop-on-Demand Bioprinting“，，，，two of the basic obstacles to DOD bioprinting’s adoption are the low speed of droplets, and the size of droplets, which is too large. Fully connected neural networks were used to solve these problems. “This paper,” state the authors, “proposed an effective multi-objective design optimization method for optimizing piezoelectric DOD printing parameters to print droplets with a smaller droplet diameter and faster droplet speed, without satellites.”
Elsewhere, seeking to subvert the3d benchy，，，，Polytechnic University of Turinresearchers have designed a benchmark test for FDM/FFF 3D printed parts. The purpose of the test is to develop a standard by which the appearance of the 3D prints can be evaluated. It identifies the most common problems that occur in FDM/FFF printing, such as stringing, blobs and zits, gaps between contours and infills, and layer separation and layer skipping among various other. Such problems might not always affect the mechanical properties of a part. But the researchers believe that if 3D printing is to become more common, a measure of ‘aesthetic’ appearance of 3D printed parts is important. A special reference part and an indicator called the Aesthetic Quality Index (AQI) was created.
作者解释说：“这项工作提出了一项初步研究，以评估3D印刷零件的美学质量。”“参考部分的设计目的是通过代表所有典型的3D打印缺陷来强调层过程的极限。”
“Moreover, a benchmarking methodology was developed to quantitatively evaluate the aesthetic quality of 3D printers through the proposed reference part.”
“评估3D印刷零件的美学质量的方法” ic published, open-access, inProcedia CIRP.
为了改善FDM/FFF打印Eric Wooldridge的另一个努力，Somerset Community College教授兼工程师表明，与基于填充的组件相比，在设计过程中如何填充固体对象，以创建更强的零件。Wooldridge呼唤这样微结构幻影孔（pH）。
According to Wooldridge, “In initial shear and flexural testing, the PH technique resulted in a 39% improvement in specimen loading performance over specimens fabricated with higher infill percentages.”
“幻影孔：与添加剂制造，典型的融合细丝制造系统一起使用的优化内部结构设计” is to be published in theInternational Journal of Rapid Manufacturing.
Ejected particles
弹射are particles thrown out after an event like an explosion or high-temperature impact occurs. In powder bed fusion methods, ejecta larger than the particle size of the raw material have been observed. However, so far their effect on the geometrical properties of a 3D printed metal part has not been studied.
In a paper titled, “Formation processes for large ejecta and interactions with melt pool formation in powder bed fusion additive manufacturing“，，，，宾夕法尼亚州立大学researchers study the origin of ejecta in powder bed fusion metal 3D printing.
The authors state, “Evidence of interference of large ejecta with melt pool formation are also reported. Such interactions between large ejecta and the melt pool are shown to significantly perturb the intended track geometry in one of two ways. Ejecta can shadow or block the laser beam then be expelled from the laser-interaction zone, or can be incorporated into the melt pool and, under some circumstances, perturb the intended track geometry.”
“有人认为，任何一种机制都可能导致缺乏融合，并可以解释PBFAM中随机缺陷的观察。”
All the experiments in this study were carried out on a ProX-320 machine by3D Systems。
保护心脏
In the UK,University of Bristol，，，，布里斯托尔大学医院，，，，Great Ormond Street Hospital for Children和维罗纳大学carried out a survey to evaluate the viability of 3D printed models of the heart. Containing anomalies in the coronary, yhe models were based on cardiac CT data and 3D printed on a表23D打印机。
根据作者的说法，“ 3D印刷的心脏模型可用于重现冠状动脉解剖结构并增强对冠状动脉异常的理解。未来的研究可以评估其成本效益，并可能探索其他印刷技术和材料。”
Full results are published online in “Evaluating 3D-printed models of coronary anomalies: a survey among clinicians and researchers at a university hospital in the UK，，，，”BMJ Open.
敲除研究应用
Using a resin-based 3D printer Dr. David Staack and Xin Tang of德克萨斯农工大学¸复制了虾的爪子。通过这样做，他们还能够创建虾来通过捕捉爪子来产生血浆的机制。
The snapping shrimp is one of the loudest animals in the sea. When its snapping claw shuts it creates a cavitation bubble with an acoustic pressure of up to 80 kPa. The bubble extends from the claw and reaches a speed of up to 100 km/h and sound of 218 decibels, strong enough to kill a fish.
Dr. Staack explained, “In our paper, we report the first direct imaging of the light emission induced by the same method the shrimp uses: the mechanically generated energy focusing on a collapsing cavitation and the following shockwave propagation.”
“The bio-inspired mechanical design allowed us to carry out repetitive and consistent experiments on the plasma generation and indicate a significant increase in conversion efficiency compared to sonic, laser and electric induced cavitation.”
“Bioinspired mechanical device generates plasma in water via cavitation，，，，“是published inScience Advances.
And finally, using 3D printing and simulation techniques, researchers at亚萨尔大学设计并建造了用于KU波段卫星通信的锥形角天线的原型。天线设计为在10.5和18.5 GHz频率内运行。
In the paper, “一个宽带ku波段锥形Corrug的原型ated Horn Antenna with 3-D Printing Technology“，，，，the makers of the antenna argue, “The proposed fabrication technique has the advantages of low weight, low cost and low production time as compared to CNC-based production in spite of the slight loss in the gain.”
“As a conclusion, 3D printing and coating method is very useful especially for research and prototype verification in antenna and microwave systems.”
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Featured image shows CrAMmed logo over an illustration of expulsion of multiple neighboring particles and their collision to form an agglomerate. Image via Scientific Reports “Formation processes for large ejecta and interactions with melt pool formation in powder bed fusion additive manufacturing.”
