Laser Micromachining of Magnetoactive Elastomers as Enabling Technology for Magneto-Responsive Surfaces

A simple method for structuring of the surface of a magnetoactive elastomer (MAE) on the tens of micrometers scale, which capabilities extend beyond conventional mold-based polymer casting, is reported. The method relies on the ablation of the material by absorption of nanosecond infrared pulses from a commercial laser. It is shown that it is possible to fabricate parallel lamellar structures with a high aspect ratio (up to 6 : 1) as well as structures with complex scanning trajectories. The method is fast (fabrication time for the 7 x 7 mm2 is about 60 s), and the results are highly reproducible. To illustrate the capabilities of the fabrication method, both orthogonal to the MAE surface and tilted lamellar structures are fabricated. These magnetosensitive lamellae can be easily bent by ±45° using an external magnetic field of about 230 mT. It is demonstrated that this bending allows one to control the sliding angle of water droplets in a great range between a sticky (>90°) and a sliding state (<20°). Perspectives on employing this fabrication technology for magneto-sensitive smart surfaces in microfluidic devices and soft robotics are discussed. Movie files show measurements of the sliding angle of water droplets. Their names include the following information: MAE__B_.avi DOI of article: 10.1002/admt.202101045

本文报道了一种可实现数十微米尺度磁活性弹性体（magnetoactive elastomer, MAE）表面结构化的简易方法，其性能突破了传统基于模具的聚合物浇铸工艺。该方法依托商用激光器发射的纳秒红外脉冲，通过材料吸收脉冲能量实现烧蚀加工。研究表明，此方法可制备高长径比（可达6:1）的平行层状结构，以及具备复杂扫描轨迹的结构。该加工方法速度快捷——制备7×7 mm²面积的样品仅需约60秒，且加工结果重复性极佳。为展示该制备方法的性能，本文分别制备了垂直于MAE表面以及倾斜式层状结构。在外加约230 mT的磁场作用下，这些磁敏感层状结构可轻松弯折±45°。实验证实，通过此种弯折可在宽范围内调控水滴的滑动角：从高黏附状态（滑动角>90°）到滑落状态（滑动角<20°）均可实现。本文还讨论了将该制备技术应用于微流控器件与软体机器人领域磁敏感智能表面的发展前景。附带的视频文件展示了水滴滑动角的测量过程，其文件名包含如下信息：MAE__B_.avi。本文DOI：10.1002/admt.202101045