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Researchers atLoughborough Universityhave developed a novel hybrid 3D printing technique that allows them to change the properties of printed parts over time, enabling a new form of 4D printing.
Named Material Treatment Extrusion Additive Manufacturing (MaTrEx-AM), the approach combines conventional extrusion-based 3D printing with a chemical treatment. Specifically, it leverages the organic chemical acetone to make targetted layers in a 3D printed object more durable. Depending on how the acetone is distributed and how much of it is applied between layers, the technique makes it possible to 3D print parts with modifiable mechanical properties, allowing users to control how they deform under load.
添加剂制造业的高级讲师，研究的合着者安迪·格拉德尔（Andy Gleadall）博士说：“新功能对于各种零件和结构而言可能是有价值的，但最明显的零件可能是在操作过程中变形，并且零件可能是在操作中变形，并且需要控制它们变形的方式。机械性能的时间依赖性性质意味着该方法为材料功能增加了新的维度，并具有原位混合处理，从而促进了真正的4D打印过程。”
Acetone and 3D printing
丙酮是一种常见的溶剂，用于从指甲油去除产品到汽油和油脂切割机。在3D打印行业中，该化合物可以用作表面修饰剂，因为它可以溶解诸如ABS之类的聚合物，从而使用户能够平滑层线以使其变得无形。Matrex-AM过程将此概念进一步迈进，在层之间的原位丙酮位于印刷零件的外部。
但是，丙酮如何改变这些印刷层的机械性能？答案在于传统的FDM 3D打印机如何挤出细丝。由于FDM系统从圆形喷嘴中沉积熔融丝，因此产生的轨道具有圆柱形形状。这导致轨道之间的接触区域相对较小，从而导致层粘结不足，最终导致较弱的部分。
Gleadall explains, “The process adds material layer-by-layer – there are grooves between the layers, a bit like you’d see if you stacked a lot of logs sideways on top of one another, all lined up. 3D printed parts are often weak because of the way layers are laid down in sequence, so there are geometric defects between the layers and the bonding of material between layers may not be as good as the pure polymer.”
通过将丙酮涂在这些圆柱轨道上，可以将它们融化在一起以更好地融合。这增加了接触面积和键的强度，从而通过选择性丙酮的应用产生可控的机械性能（和可编程变形曲线）。
头盔填充物和生物医学植入物
Gleadall的团队发现，通过施加丙酮，他们可以将PLA和ABS零件的可塑性提高25至16倍，从而增加处理区域的韧性。但是，从长远来看，这些零件的机械性能已回收到其原始值高达90％，这是4D的进来。此次恢复发生在ABS的三个小时之内，而PLA标本最多需要60天恢复。重要的是，即使印刷零件回收了其性质，当时进行的任何几何变化都保留了。
根据拉夫堡团队,真实applications of MaTrEx-AM include 4D lattice structures for impact-resistant helmet padding, as well as dynamic biomedical implants that deform along with the anatomy of the patient.
更多细节的研究可以发现paper titledMaTrEx AM: A new hybrid additive manufacturing process to selectively control mechanical properties.
In the academic sphere, 4D printing has proven itself to be a great tool for applications such as medical devices and soft robots. Researchers from theUniversity of Freiburgand theUniversity of Stuttgart最近开发了一种新颖的方法4D打印可穿戴的腕部夹板自我调整to the anatomy of the patient. Inspired by the propagation mechanism of the air potato plant (Dioscorea bulbifera), the printed system can be pre-programmed to carry out complex movements when exposed to moisture.
在其他地方，在Tianjin University, China, scientists recently4D打印了自我宣传的软机器人能够独自漫游。管形机器人由一种称为液晶弹性体的材料制成，与热量接触时会自组装。该设备利用巧妙编程的折叠图案在其身体内部诱发应变，这使其能够像日志一样翻转。
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Featured image shows Loughborough University campus. Photo via Loughborough University.
