Department of Materials Science and Engineering, Henry Samueli School of Engineering and Applied Science , University of California , Los Angeles , California 90095 , United States.
Acc Chem Res. 2019 Feb 19;52(2):316-325. doi: 10.1021/acs.accounts.8b00516. Epub 2019 Jan 30.
Creating an artificial muscle has been one of the grand challenges of science and engineering. The invention of such a flexible, versatile, and power efficient actuator opens the gate for a new generation of lightweight, highly efficient, and multifunctional robotics. Many current artificial muscle technologies enable low-power mobile actuators, robots that mimic efficient and natural forms of motion, autonomous robots and sensors, and lightweight wearable technologies. They also have serious applications in biomedical devices, where biocompatibility, from a chemical, flexibility, and force perspective, is crucial. It remains unknown which material will ultimately form the ideal artificial muscle. Anything from shape memory alloys (SMAs) to pneumatics to electroactive polymers (EAPs) realize core aspects of the artificial muscle goal. Among them, EAPs most resemble their biological counterparts, and they encompass both ion-infusion and electric field based actuation mechanisms. Some of the most investigated EAPs are dielectric elastomers (DEs), whose large strains, fracture toughness, and power-to-weight ratios compare favorably with natural muscle. Although dielectric elastomer actuators (DEAs) only entered the artificial muscle conversation in the last 20 years, significant technological progress has reflected their high potential. Research has focused on solving the core issues surrounding DEAs, which includes improving their operational ranges with regard to temperature and voltage, adding new functionality to the materials, and improving the reliability of the components on which they depend. Mechanisms designed to utilize their large-strain actuation and low stiffness has also attracted attention. This Account covers important research by our group and others in various avenues such as decreasing viscoelastic losses in typical DE materials, increasing their dielectric constant, and countering electromechanical instability. We also discuss variable stiffness polymers, specifically bistable electroactive polymers, which, notably, open DEAs to structural applications typically unattainable for soft-actuator technologies. Furthermore, we explore advancements related to highly compliant and transparent electrodes, a crucial component of DEAs capable of achieving high actuation strain. We then cover noteworthy applications, including several novel devices for soft robotics and microfluidics, and how those applications fit within other major developments in the field. Finally, we conclude with a discussion of the remaining challenges facing current DEA technology and speculate on research directions that may further advance DE-based artificial muscles as a whole. This Account serves as a stepping stone into the field of EAPs, which, through the work of researchers worldwide, are positioned as a potential challenger to conventional actuator technologies.
制造人工肌肉一直是科学和工程领域的一大挑战。发明这种灵活、多功能且高效能的致动器为新一代轻量级、高效能和多功能机器人开辟了道路。许多现有的人工肌肉技术可实现低功率移动致动器、模仿高效和自然运动形式的机器人、自主机器人和传感器以及轻量级可穿戴技术。它们在生物医学设备中也有重要应用，其中从化学、灵活性和力的角度来看，生物兼容性至关重要。目前还不清楚哪种材料最终将成为理想的人工肌肉。从形状记忆合金 (SMA) 到气动到电活性聚合物 (EAP)，各种材料都实现了人工肌肉目标的核心方面。其中，EAP 最类似于它们的生物对应物，并且它们都包含离子注入和电场驱动机制。最受研究的 EAP 之一是电介质弹性体 (DE)，其大应变、断裂韧性和功率重量比与天然肌肉相当。尽管电介质弹性体致动器 (DEA) 仅在过去 20 年才进入人工肌肉讨论，但它们的重大技术进步反映了它们的高潜力。研究的重点是解决 DEA 面临的核心问题，包括改善其在温度和电压方面的工作范围、为材料增加新功能以及提高其依赖的组件的可靠性。旨在利用其大应变致动和低刚度的机制也引起了关注。本账户涵盖了我们小组和其他小组在各种途径的重要研究，例如减少典型 DE 材料中的粘弹性损耗、提高介电常数以及对抗机电不稳定性。我们还讨论了可变刚度聚合物，特别是双稳态电活性聚合物，值得注意的是，它们使 DEA 能够应用于通常无法实现软致动技术的结构应用。此外，我们探讨了与高度顺应性和透明电极相关的进展，这是能够实现高致动应变的 DEA 的关键组件。然后，我们介绍了一些值得注意的应用，包括软机器人和微流控领域的几个新型设备，以及这些应用如何融入该领域的其他主要发展。最后，我们讨论了当前 DEA 技术面临的剩余挑战，并推测了可能进一步推进整个基于 DE 的人工肌肉的研究方向。本账户是电活性聚合物领域的一个垫脚石，通过世界各地研究人员的工作，电活性聚合物被定位为传统致动器技术的潜在挑战者。
