A team of researchers fromLinköpingUniversity, Sweden, has developed a set of microactuators for soft micro robotics using a custom-built extrusion-based 3D printer. The actuators contain an electrically-active polymer that changes shape – after being printed – in the presence of an electrical charge, granting them 4D capabilities.
While 4D printed soft robots are usually limited to the centi- or milli-scale, the specially developed technology allowed the researchers to scale down their actuation mechanisms to微米结构域，厚度约为20微米。他们声称他们的自定义机器具有通用性和可扩展性，并希望使用以前看不见的复杂微型机器人“拓宽软机器人的权限”。
Electroactive polymer technology
Electroactive polymer (EAP) technology is the driving force behind many soft robotic devices. It describes materials that activate, or actuate when subjected to an electrical charge. In soft robots, this is comparable to a muscle contraction (and often looks like one).
根据研究人员的说法，试图缩小EAP执行器的规模通常会面临许多挑战。显微加工技术（例如光刻）能够启用较低的致动潜力和较高的功率重量比，但往往涉及复杂的处理。这使得将它们与当前市场和技术集成在一起变得困难。
This is where additive manufacturing offers a plethora of benefits, as products can be modified on the fly, energy costs can be cut significantly, and waste production can be reduced ten-fold. Ultimately, the team believes this may make EAP devices cheaper and feasible for a broader range of applications.
4D printed microactuators
The first stage of the study involved building the printer. The basis of the machine was a three-axis programmable CNC stage kitted out with a high-precision fluid dispensing system. Attached to the dispensing system was a 5mL lock syringe, whereby the extrusion rate was controlled by the lateral motion of the stage. The team used a commercially available glass slide as the build plate.
They first placed a thin layer of gold, just 40nm thick, on the glass slide to form a conductive layer. The researchers then used the syringe to dispense a single layer of UV curableurethane acrylate gel onto the conductive layer. The gel would go on to form the ‘body and arms’ of the microactuator. Once the gel was fully cured under UV light, the team deposited a layer of polypyrrole (the EAP) onto the other side of the gold sheet.
该团队设法多次重复此过程，打印微型射击器的长度从5000微米一直到1000微米不等。他们开发的最薄的显微厌恶仪仅为20微米。研究人员发现，与其他3D打印方法的典型1KV+相比，他们可以用电势较小的电势启动设备。科学家认为，他们的作品具有通过3D打印技术开发的低成本微型机器人技术的微型化的巨大潜力。
Further details of the study can be found in the paper titled ‘3D Printing Microactuators for Soft Microrobots’. It is co-authored byManav Tyagi,Geoffrey M. Spinks， 和埃德温·W.H.贾格。
当涉及到4D打印的软机器人时，有许多不同的致动方法 - 电动驱动是其中之一。来自莱斯大学最近4 d印刷自己的软机器人activated by changes in temperature. They intend to develop the technology to the point where it can be used in biomedical implants that reconfigure themselves on demand.
在其他地方，在南南技术大学, researchers have taken this a step further and printed soft robots that don’t require any real-time human input at all. The process involvesswelling an elastomer with ethanol诱导执行器结构中的压力。随着乙醇自身蒸发，弹性体干燥，材料被固有存储在其中的弹性能变形。
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特色图片显示了最小的4D印刷微型机器人。通过LinköpingUniversity的照片。
