Materials

加州大学圣塔芭芭拉(UC Santa Barbara)UC研究人员开发了第一个3D可打印的“瓶洗”弹性体

Researchers from theUniversity of California at Santa Barbara(UC Santa Barbara) have developed a 3D printable “bottlebrush” elastomer with softness and elasticity resembling that of human tissue.

博士后研究人员Renxuan Xie和Sanjoy Mukherjee偶然地偶然发现了新的弹性体,同时试图为其他项目开发材料。在观察其超柔软和形状的属性之后,他们意识到他们可以使用直接墨水写入(DIW)打印3D弹性体以创建墨水,然后通过涂抹紫外线将弹性体返回其实心形式。

According to Xie and Mukherjee, being able to 3D print bottlebrush elastomers makes it possible to harness their unique mechanical properties for applications such as biomimetic tissue and high-sensitivity electronic devices like touch pads, sensors, and actuators, which require close control over an object’s dimensions.

Christopher Bates, an assistant professor at UC Santa Barbara and laboratory leader, said of the accidental discovery:

“当我们看到这种明确定义的压力时,它集体地使每个人都可以打印出3D,这很酷,因为我们知道的3D可打印材料都没有这种超柔软的属性。”

瓶洗弹性体的独立性

Bottlebrush polymers have been around for more than two decades, and differ from conventional elastomers, or rubbers, as a result of their structure. While conventional elastomers are stiffer than many biological tissues due to being made up of long and entangled linear molecules, bottlebrush polymers have additional polymers attached to their linear backbone. This structure looks similar to that of a bottlebrush one may find in a kitchen, hence the name, and enables the polymer to form extremely soft elastomers.

As far as the researchers are aware, despite being around for years bottlebrush polymers haven’t been 3D printed before, making UC Santa Barbara’s new material all the more unique.

“The field has exploded in the past ten years thanks to advances in synthetic chemistry that provide exquisite control over the size and shape of these unique molecules,” continued Bates. “These super-soft elastomers might be applicable as implants. You may be able to reduce inflammation and rejection by the body if the mechanical properties of an implant match native tissue.”

Soft and flexible polymers have been previously utilized in the development of 3D printed implants, an example of which is the production of asoft neural implantby researchers atMassachusetts Institute of Technology(MIT) which conforms to the contours of the brain to monitor activity over long periods of time. The use of 3D printed flexible polymer electronics can potentially provide a softer, safer, and faster alternative to existing metal-based implants.

在其他地方,软材料和电子产品也已合并为开发3D printed prototype neural implant有可能治疗神经系统损伤,例如瘫痪,并创造3D打印的生物传感器for the wireless monitoring of blood flow.Soft polymer-based 3D printing materialsare also used within the dental sector for the production of clear aligners, flexible dentures, and crowns.

Several researchers utilized 3D printing to make medical breakthroughs in September, not least those at Sheffield University who printed a neural implant (pictured). Photo via Sheffield University.
Neural interfaces could lead to the next generation of medical treatments for patients with nervous system problems. Image via Sheffield.ac.uk.

3D打印瓶洗弹性弹性体

最初的发现集中在纳米长度尺度上的瓶洗聚合物的自组装周围。该材料被归类为屈服压力液体,是一种半柔软的固体,具有其形状,类似于黄油,但是一旦施加了足够的压力,酒就会呈液体。这意味着研究人员可以通过DIW 3D打印过程以墨水形式打印材料。

As the material is capable of holding its shape for hours, it can be tuned to flow under various amounts of pressure, such as when vibration is present, to suit the desired processing conditions without impacting the structural stability of the printed part. Once the object had been printed, the researchers exposed it to UV light in order to activate crosslinkers within the ink formulation. These crosslinkers link up the bottlebrush polymers to form a super-soft elastomer that becomes a permanent solid, meaning it will no longer liquify under pressure.

Xie explained: “We start with long polymers that are not crosslinked. That allows them to flow like a fluid. But, after you shine the light on them, the small molecules between the polymer chains react and are linked together into a network, so you have a solid, an elastomer that, when stretched, will return to its original shape.”

材料的柔软度是根据其模量来测量的 - 从本质上讲,它的伸展程度很容易 - 对于大多数弹性体而言,这可以与橡皮筋的弹性体进行比较。Xie和Mukherjee的材料的模量比橡皮筋小1000倍,这意味着它非常柔软且富有弹力。实际上,瓶洗弹性体的长度可以伸展到其长度的三到四倍。

从左开始:未链接聚合物墨水,用于激活交联的红外光和最终产物 - 一种超柔软的超弹性交联弹性体。
从左开始:未链接聚合物墨水,用于激活交联的红外光和最终产物 - 一种超柔软的超弹性交联弹性体。Image via Isabelle Chabinyc/UC Santa Barbara.

A “pure” polymer

Another factor that makes the researchers’ material unique is that it contains no water or other solvent in order to make it artificially softer. Conventional polymers are reliant on containing the right amount of water in order to maintain their structures, however the bottle brush elastomer is all solid, so its form will not change.

“People often add solvent to liquify a solid so that it can be squeezed out of a nozzle,” Xie added. “But if you add solvent, it has to evaporate after printing causing the object to change its shape or crack.”

研究人员认为,无溶剂的制造过程对于使打印过程尽可能干净和轻松尤其有利。所得的材料“感觉非常像人体组织”,并且在仿生组织和高敏化电子中具有多种潜在应用。

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Featured image showsfrom left: the unlinked polymer ink, infrared light being applied to activate the crosslinks, and the final product — a super-soft, super-elastic crosslinked elastomer. Image via Isabelle Chabinyc/UC Santa Barbara.