Dallinger Alexander, Kindlhofer Paul, Greco Francesco, Coclite Anna Maria
Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Graz 8010, Austria.
ACS Appl Polym Mater. 2021 Apr 9;3(4):1809-1818. doi: 10.1021/acsapm.0c01385. Epub 2021 Mar 9.
The method of converting insulating polymers into conducting 3D porous graphene structures, so-called laser-induced graphene (LIG) with a commercially available CO laser engraving system in an ambient atmosphere, resulted in several applications in sensing, actuation, and energy. In this paper, we demonstrate a combination of LIG and a smart hydrogel (poly(-vinylcaprolactam)-pNVCL) for multiresponsive actuation in a humid environment. Initiated chemical vapor deposition (iCVD) was used to deposit a thin layer of the smart hydrogel onto a matrix of poly(dimethylsiloxane) (PDMS) and embedded LIG tracks. An intriguing property of smart hydrogels, such as pNVCL, is that the change of an external stimulus (temperature, pH, magnetic/electric fields) induces a reversible phase transition from a swollen to a collapsed state. While the active smart hydrogel layer had a thickness of only 300 nm (compared to the 500 times thicker actuator matrix), it was possible to induce a reversible bending of over 30° in the humid environment triggered by Joule heating. The properties of each material were investigated by means of scanning electron microscopy (SEM), Raman spectroscopy, tensile testing, and ellipsometry. The actuation performances of single-responsive versions were investigated by creating a thermoresponsive PDMS/LIG actuator and a humidity-responsive PDMS/pNVCL actuator. These results were used to tune the properties of the multiresponsive PDMS/LIG/pNVCL actuator. Furthermore, its self-sensing capabilities were investigated. By getting a feedback from the piezoresistive change of the PMDS/LIG composite, the bending angle could be tracked by measuring the change in resistance. To highlight the possibilities of the processing techniques and the combination of materials, a demonstrator in the shape of an octopus with four independently controllable arms was developed.
利用市售的CO激光雕刻系统在环境气氛中将绝缘聚合物转化为导电三维多孔石墨烯结构（即所谓的激光诱导石墨烯，LIG）的方法，已在传感、驱动和能源等多个领域得到应用。在本文中，我们展示了LIG与智能水凝胶（聚（乙烯基己内酰胺）-pNVCL）相结合，用于在潮湿环境中的多响应驱动。采用引发化学气相沉积（iCVD）将智能水凝胶薄层沉积到聚二甲基硅氧烷（PDMS）和嵌入式LIG轨迹的基质上。智能水凝胶（如pNVCL）的一个有趣特性是，外部刺激（温度、pH值、磁场/电场）的变化会引起从溶胀状态到塌陷状态的可逆相变。虽然活性智能水凝胶层的厚度仅为300纳米（与厚500倍的致动器基质相比），但在焦耳热引发的潮湿环境中，仍可诱导超过30°的可逆弯曲。通过扫描电子显微镜（SEM）、拉曼光谱、拉伸测试和椭偏仪对每种材料的性能进行了研究。通过制作热响应性PDMS/LIG致动器和湿度响应性PDMS/pNVCL致动器，研究了单响应版本的驱动性能。这些结果被用于调整多响应PDMS/LIG/pNVCL致动器的性能。此外，还研究了其自传感能力。通过从PMDS/LIG复合材料的压阻变化获得反馈，可以通过测量电阻变化来跟踪弯曲角度。为了突出加工技术和材料组合的可能性，则开发了一个具有四个可独立控制臂的章鱼形状的演示器。
