Artificial Muscles: Mechanisms, Applications, and Challenges

Mirvakili, Seyed Mohammad; Hunter, Ian W.

doi:10.1002/adma.201704407

Cited by 798 publications

(736 citation statements)

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“…[1][2][3] Soft robots offer an intrinsic adaptability and dexterity that is well-suited for safe operation near humans, opening applications in wearable, surgical and collaborative robotics. [3,[8][9][10] Soft actuators that mimic the universal performance of natural muscle [11,12] are critical components for creating the next generation of soft robots that achieve levels of functionality seen only in biological systems. [3,[8][9][10] Soft actuators that mimic the universal performance of natural muscle [11,12] are critical components for creating the next generation of soft robots that achieve levels of functionality seen only in biological systems.…”

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confidence: 99%

An Easy‐to‐Implement Toolkit to Create Versatile and High‐Performance HASEL Actuators for Untethered Soft Robots

et al. 2019

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For soft robots to have ubiquitous adoption in practical applications they require soft actuators that provide well‐rounded actuation performance that parallels natural muscle while being inexpensive and easily fabricated. This manuscript introduces a toolkit to rapidly prototype, manufacture, test, and power various designs of hydraulically amplified self‐healing electrostatic (HASEL) actuators with muscle‐like performance that achieve all three basic modes of actuation (expansion, contraction, and rotation). This toolkit utilizes easy‐to‐implement methods, inexpensive fabrication tools, commodity materials, and off‐the‐shelf high‐voltage electronics thereby enabling a wide audience to explore HASEL technology. Remarkably, the actuators created from this easy‐to‐implement toolkit achieve linear strains exceeding 100%, a specific power greater than 150 W kg −1 , and ≈20% strain at frequencies above 100 Hz. This combination of large strain, extreme speed, and high specific power yields soft actuators that jump without power‐amplifying mechanisms. Additionally, an efficient fabrication technique is introduced for modular designs of HASEL actuators, which is used to develop soft robotic devices driven by portable electronics. Inspired by the versatility of elephant trunks, the above capabilities are combined to create an untethered continuum robot for grasping and manipulating delicate objects, highlighting the wide potential of the introduced methods for soft robots with increasing sophistication.

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confidence: 99%

An Easy‐to‐Implement Toolkit to Create Versatile and High‐Performance HASEL Actuators for Untethered Soft Robots

et al. 2019

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“…In particular, because spores do not adhere strongly to each other, approaches that strengthen spore-spore interactions are needed. [1][2][3][4][5][6] The potency of these systems is presently limited by the performance and the practicality of their requisite actuators. These mixtures were then deposited onto plastic films to create various actuators and energy harvesting devices.…”

mentioning

confidence: 99%

“…[1][2][3][4][5][6] The potency of these systems is presently limited by the performance and the practicality of their requisite actuators. [1][2][3][4][5][6] The potency of these systems is presently limited by the performance and the practicality of their requisite actuators.…”

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confidence: 99%

“…Otherwise, individual spores can slip across each other during expansion and contraction, or cracks may occur within the actuator due to stress. [42] They also withstand pH values in a broad range (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) unless there is a strong sporicidal chemical in the solution. We found that commercially available optical and electronical adhesives have been used in applications which have tight requirements for low moisture sensitivity.…”

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confidence: 99%

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Spore‐Based Water‐Resistant Water‐Responsive Actuators with High Power Density

Çakmak

Tinay

Chen

et al. 2019

Adv Materials Technologies

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require external stimuli such as high electric fields, or high temperatures and pressures. [1,2] These materials can be driven by perturbations to the ambient humidity or with natural fluctuations. [7,8] A variety of materials, such as graphene oxide, [9][10][11][12] polymers, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] liquid crystals, [14,29,30] paper, [31,32] and biologically based materials [6][7][8][33][34][35][36] can serve as hygroscopic actuators. These actuators exhibit curling and folding, [10,14,19] walking, [17,21,24,37] gripping, [18] and power generation functions. [7,8,38] Despite the potential of humidityresponsive materials, relatively low work densities and slow responses limit the scope of applications. Studies of hygroscopic properties of Bacillus spores have shown that these dormant microorganisms exhibit actuation capabilities, with energy densities up to about 20 MJ m −3 , which raise the possibility of using spores as building blocks of macroscopic actuators. [8] However, assembly of spores into larger materials while retaining their actuation performance presents challenges. In particular, because spores do not adhere strongly to each other, approaches that strengthen spore-spore interactions are needed. Therefore, initial demonstrations of spore-based actuators used mixtures of spores with water soluble adhesives. These mixtures were then deposited onto plastic films to create various actuators and energy harvesting devices. [7] However, the resulting materials exhibited low work density and specific work in comparison to individual spores. Importantly, while water soluble adhesives simplify the fabrication process, they are prone to degradation when placed in direct contact with water, making it difficult to use in waterdriven applications. Therefore, different approaches are needed to enhance the work density and robustness of spore-based materials.Here, we report spore-based actuators that use waterresistant UV-curable adhesives and achieve work densities up to 0.44 MJ m −3 , which is an order of magnitude higher than the synthetic humidity-responsive polymers. [22][23][24][25] The water resistance of the spore-based actuators allowed direct waterdriven actuation, which reduced the response times by nearly 100-fold. We also leveraged the UV curability of these adhesives to facilitate rapid fabrication of complex dynamic and/or adaptive structures using photolithography.Bacillus subtilis spores exhibit hygroscopic actuation capabilities (Figure 1c) and have shown high energy densities Active materials and surfaces that are less intrusive and more compatible with humans and their environment are critical for robotic applications. Humidity-and water-responsive materials are emerging as versatile alternatives to commonly used actuators in robotic systems, due to ease of actuation with humidity gradients and pervasiveness of water in the environment. However, these materials exhibit relatively low work densities and slow responses, and they are degraded when placed in ...

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“…[20,21] The contracting and recovery speeds are comparable to previously reported LCEbased soft robots. [29] We next explore light-powered multidirectional rolling of the tensegrity robot through the actuation of one LCE-CNT composite fiber. Based on the stress versus stretch diagram of a passive LCE-CNT composite fiber as shown in Figure 1B, we can calculate the corresponding actuating stress generated by the actuated fiber during the laser irradiation as plotted in Figure 1D.…”

Section: Light-powered Robotsmentioning

confidence: 99%

A Light‐Powered Ultralight Tensegrity Robot with High Deformability and Load Capacity

et al. 2018

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Traditional hard robots often require complex motion‐control systems to accomplish various tasks, while applications of soft‐bodied robots are limited by their low load‐carrying capability. Herein, a hybrid tensegrity robot composed of both hard and soft materials is constructed, mimicking the musculoskeletal system of animals. Employing liquid crystal elastomer–carbon nanotube composites as artificial muscles in the tensegrity robot, it is demonstrated that the robot is extremely deformable, and its multidirectional locomotion can be entirely powered by light. The tensegrity robot is ultralight, highly scalable, has high load capacity, and can be precisely controlled to move along different paths on multiterrains. In addition, the robot also shows excellent resilience, deployability, and impact‐mitigation capability, making it an ideal platform for robotics for a wide range of applications.

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Artificial Muscles: Mechanisms, Applications, and Challenges

Cited by 798 publications

References 235 publications

An Easy‐to‐Implement Toolkit to Create Versatile and High‐Performance HASEL Actuators for Untethered Soft Robots

An Easy‐to‐Implement Toolkit to Create Versatile and High‐Performance HASEL Actuators for Untethered Soft Robots

Spore‐Based Water‐Resistant Water‐Responsive Actuators with High Power Density

A Light‐Powered Ultralight Tensegrity Robot with High Deformability and Load Capacity

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