Enabling variable-stiffness hand rehabilitation orthoses with dielectric elastomer transducers

Carpi, Federico; Frediani, Gabriele; Gerboni, Carlo A.; Gemignani, Jessica; Rossi, Danilo De

doi:10.1016/j.medengphy.2013.10.015

Cited by 67 publications

(38 citation statements)

References 13 publications

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“…Their capacity to rapidly, dramatically, and reversibly change rigidity is also attractive for artificial muscle actuators, which are becoming increasingly suitable for wearable devices. The goal of rigidity tuning has been addressed using methods like solvent interactions, pneumatic jamming, electrostatic adhesion, antagonistic actuator architectures, fluidic flexible matrix composites, phase‐change materials, and magnetorheological fluids . The diversity of these methods results in an equally diverse range of technical challenges, such as long activation times, high activation voltages, limited scalability and structural versatility, and a dependence on bulky auxiliary equipment .…”

Section: Comparison Between Thermally Activated Stiffness‐tuning Methmentioning

confidence: 99%

Liquid Metal‐Conductive Thermoplastic Elastomer Integration for Low‐Voltage Stiffness Tuning

Rich

Jang

Park

et al. 2017

Adv Materials Technologies

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and reversibly change rigidity is also attractive for artificial muscle actuators, [5,6] which are becoming increasingly suitable for wearable devices. The goal of rigidity tuning has been addressed using methods like solvent interactions, [7] pneumatic jamming, [8,9] electrostatic adhesion, [10] antagonistic actuator architectures, [11][12][13] fluidic flexible matrix composites, [14] phase-change materials, [15][16][17][18][19][20][21][22][23][24][25][26][27] and magnetorheological fluids. [28] The diversity of these methods results in an equally diverse range of technical challenges, such as long activation times, high activation voltages, [10,15] limited scalability and structural versatility, [11][12][13]26,27] and a dependence on bulky auxiliary equipment. [8,9,14,17,28] At present, there remains to be an electrically powered method for reversible rigidity tuning that exhibits <5 s, <20 V, actuation in a size-scalable architecture that allows for integration into a wide range of systems.In this work, we introduce a rigiditytuning material architecture that changes stiffness in response to moderate electrical voltage (Figure 1a,b and Video S1 (Supporting Information)). Furthermore, we demonstrate its feasibility in both tensile and flexural applications, via an active tendon in an underactuated robotic finger model [29] and a moldable splint (Figure 1c,d). The tendon consists of a conductive thermoplastic elastomer (cTPE) coated with a ≈10-140 µm layer of spray-deposited eutectic gallium-indium liquid metal alloy (EGaIn) [30] and embedded in a silicone matrix ( Figure 1b). Applying voltage to the EGaIn electrodes causes electric current to travel through the cTPE element. This induces rapid Joule heating in the cTPE, bringing it to the melting temperature, above which it softens and can no longer support a tensile load. When current is removed, the element cools and solidifies, and its stiffness is restored. Previously, shape memory polymers (SMPs) [16,[18][19][20][23][24][25]31] and low-melting-point alloys [20][21][22]26,27,32] have also been incorporated into reversible, stiffness-based adhesives and rigidity-tuning elements. Although some of these methods may have very large stiffness change ratios, they typically require external heating equipment or long activation times ( Table 1). Shan et al. exploited Joule heating to directly electrically activate cTPE; however, this technique required activation voltages of above 100 V. [15] We build on previous work with cTPE by introducing a novel design, in which a pair of liquid metal electrodes is oriented on opposite sides of the cTPE. This configuration minimizes the An electrically responsive composite is introduced that exhibits muscle-like changes in elastic stiffness (≈1-10 MPa) when stimulated with moderate voltages (5-20 V). The stiffness-tuning element contains an embedded layer of conductive thermoplastic elastomer (cTPE), composed of a propylene-ethylene copolymer and a percolating network of carbon black. Two opposite surfaces of the cTPE layer ar...

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Section: Comparison Between Thermally Activated Stiffness‐tuning Methmentioning

confidence: 99%

Liquid Metal‐Conductive Thermoplastic Elastomer Integration for Low‐Voltage Stiffness Tuning

Rich

Jang

Park

et al. 2017

Adv Materials Technologies

View full text Add to dashboard Cite

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“…Multiple strategies have been pursued recently to achieve stiffness tunability, including pneumatic jamming, [ 3,5,6 ] chemical interactions, [ 7 ] opposing actuator structures, [ 8–10 ] magnetorheological fluids, [ 11,12 ] external/internal heating of materials with phase change [ 13–24 ] or glass transition, [ 25–28 ] or through combinations of these techniques. [ 13,29 ] Among phase‐changing materials, low melting point alloys (LMPA) have been used widely as they are highly electrically conductive, rigid as metal at room temperature, and their melting point can be as low as 47.2 °C [ 21 ] or 62.0 °C.…”

Section: Figurementioning

confidence: 99%

Robust Three‐Component Elastomer–Particle–Fiber Composites with Tunable Properties for Soft Robotics

Nasab

Sharifi

Chen

et al. 2020

Advanced Intelligent Systems

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The ability to tune the mechanical stiffness between a soft state and a rigid state is essential for various living systems to navigate nature. Examples for this range from muscle-powered motor tasks and sexual reproduction, to spontaneous change in shape for predator evasion. [1] Similar to their natural counterparts, engineered materials with tunable properties including mechanical stiffness have the potential to be used in a broad range of engineering applications. [1,2] Structures made with these materials can change their mechanical rigidity in static or dynamic systems to extend their workspace. [1-4] Multiple strategies have been pursued recently to achieve stiffness tunability, including pneumatic jamming, [3,5,6] chemical interactions, [7] opposing actuator structures, [8-10] magnetorheological fluids, [11,12] external/internal heating of materials with phase change [13-24] or glass transition, [25-28] or through combinations of these techniques. [13,29] Among phase-changing materials, low melting point alloys (LMPA) have been used widely as they are highly electrically conductive, rigid as metal at room temperature, and their melting point can be as low as 47.2 C [21] or 62.0 C. [20] LMPA layers, channels, foams, lattices, and particles have been incorporated as fillers into soft elastomers and shape memory polymers to create engineering materials with stiffness tunability. [13,17,18,20-23] In addition to tuning mechanical stiffness, LMPA fillers can also enhance the thermal and electrical properties of the composites. [18,30,31] Another example of smart composites with tunable stiffness containing phase-changing components is conductive propylene-based elastomers (CPBE), [24] which have a propylene-ethylene copolymer elastomer matrix and dispersed

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“…In real applications, it is worth noting that the first mass-produced application of dielectric elastomer technology has been for a wearable system (a vibrating haptic-feedback device for a gaming headset) and it uses high voltages [148]. In [149], dielectric elastomers are also being explored extensively for biomedical applications. In order to boost DEAs for industrial exploitation, other technologies are also investigated to drive the DEAs with lower voltage.…”

Section: Designmentioning

confidence: 99%

Analysis and application of a rolled dielectric elastomer actuator with two degrees of freedom

Wang

Zhu

et al. 2016

Smart Mater. Struct.

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Conventional industrial robots with the rigid actuation technology have made great progress for humans in the fields of automation assembly and manufacturing. With an increasing number of robots needing to interact with humans and unstructured environments, there is a need for soft robots capable of sustaining large deformation while inducing little pressure or damage when maneuvering through confined spaces. The emergence of soft robotics offers the prospect of applying soft actuators as artificial muscles in robots, replacing traditional rigid actuators. Dielectric elastomer actuators (DEAs) are recognized as one of the most promising soft actuation technologies due to the facts that: i) dielectric elastomers are kind of soft, motion-generating materials that resemble natural muscle of humans in terms of force, strain (displacement per unit length or area) and actuation pressure/ density; ii) dielectric elastomers can produce large voltage-induced deformation. In this survey, we first introduce the so-called DEAs emphasizing the key points of working principle, key components and electromechanical modeling approaches. Then, different DEA-driven soft robots, including wearable/humanoid robots, walking/serpentine robots, flying robots and swimming robots, are reviewed. Lastly, we summarize the challenges and opportunities for the further studies in terms of mechanism design, dynamics modeling and autonomous control.

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Enabling variable-stiffness hand rehabilitation orthoses with dielectric elastomer transducers

Cited by 67 publications

References 13 publications

Liquid Metal‐Conductive Thermoplastic Elastomer Integration for Low‐Voltage Stiffness Tuning

Liquid Metal‐Conductive Thermoplastic Elastomer Integration for Low‐Voltage Stiffness Tuning

Robust Three‐Component Elastomer–Particle–Fiber Composites with Tunable Properties for Soft Robotics

Analysis and application of a rolled dielectric elastomer actuator with two degrees of freedom

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