Siloxane-based thin films for biomimetic low-voltage dielectric actuators
Siloxane-based thin films for biomimetic low-voltage dielectric actuators
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DOI：
10.1016/j.sna.2015.06.014
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发表时间：
2015-09-01
影响因子：
4.6
通讯作者：
Mueller, Bert
中科院分区：
文献类型：
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作者：
Toepper, Tino;Weiss, Florian;Mueller, Bert
采用分子束沉积硅氧烷基聚合物薄膜的方法实现了单层介质弹性体驱动器。在高真空条件下，相对分子质量为6000和28,000 g/mol的端乙烯基聚二甲基硅氧烷(PDMS)在100~180℃的温度下蒸发，沉积速率和可实现膜厚均与坩埚温度呈线性关系，且相对分子质量较低的PDMS的沉积速率和可实现膜厚度显著增加。在180℃下，薄膜的沉积速率为(130+/-5)nm/h，最大膜厚为(530+/-1)nm，最佳生长条件为6000g/mol。观察到热诱导聚合将封端氢化物的PDMS的最高可达蒸发温度限制在180℃以上，将封端乙烯基的PDMS的最高可达蒸发温度限制在230℃以上。通过链上官能化的乙烯基端基上的自由基，成功地建立了封端乙烯基的光诱导聚合。原子力显微镜纳米压痕显示，低聚物链的长度决定了聚合物层的弹性模数。作为非对称悬臂梁结构，弯曲特性表明，与在100到800 V之间工作的4微米厚的旋涂薄膜相比，在1到12 V的电压范围内激活的200 nm薄膜保持了致动。目前的200 nm薄膜悬臂致动器的作用力约为10(-4)N，这意味着具有超过10(4)层的多层致动器将达到与自然肌肉相当的力。因此，这种纳米结构有资格用于医疗应用，例如治疗严重的尿失禁。(C)2015年提交人。爱思唯尔出版公司(Elsevier B.V.)
Molecular beam deposition of siloxane-based polymer thin films was employed to realize single-layer dielectric elastomer actuators. With molecular weights of 6000 and 28,000 g/mol, vinyl-terminated polydimethylsiloxane (PDMS) was evaporated under high-vacuum conditions at crucible temperatures between 100 and 180 degrees C. Both deposition rate and realizable film thickness showed linear dependency with respect to the crucible temperature and were significantly higher for PDMS with lower molecular weight. Optimized growth conditions for 6000 g/mol were obtained at 180 degrees C with a deposition rate of (130 +/- 5) nm per hour and a maximal film thickness of (530 +/- 1) nm. Thermally induced polymerization was observed to limit the maximum accessible evaporation temperature for hydride-terminated PDMS above 180 degrees C and for vinyl-terminated PDMS above 230 degrees C. Ultraviolet (UV) light induced polymerization of vinyl-terminated PDMS was successfully established via radicalization at the functional vinyl end groups of the chains. Atomic force microscopy nanoindentation of the UV-polymerized network reveals that the oligomer chain length determines the elastic modulus of the polymer layer. Manufactured as asymmetric cantilever structures, the bending characteristic gave evidence that a 200 nm-thin film, activated in the voltage range between 1 and 12 V, maintains the actuation compared to a 4 mu m-thick, spin-coated film, operated between 100 and 800 V. The force of the presented 200 nm-thin film cantilever actuator was about 10(-4) N. This means that a multilayer actuator with more than 10(4) layers would reach forces comparable to natural muscles. Therefore, such nanostructures can qualify for medical applications for example to treat severe incontinence. (C) 2015 The Authors. Published by Elsevier B.V.