Soft and Deformable Sensors Based on Liquid Metals

Kim, Taeyeong; Kim, Dongmin; Lee, Bong Jae; Lee, Jungchul

doi:10.3390/s19194250

Cited by 62 publications

(52 citation statements)

References 103 publications

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“…Different solid and liquid materials have been used for the encapsulation of the electrodes including PDMS, Ecoflex, silicone, polyimide, and hydrogels, each of which exhibit different flexing and stretching capabilities in addition to different properties which makes them suitable for different ranges of applications (e.g., air permeability, water permeability, cost, curing temperature, etc.). [273,[277][278][279]…”

Section: Electrodes For Soft Actuatorsmentioning

confidence: 99%

Soft Actuators for Soft Robotic Applications: A Review

El‐Atab

Mishra

Al‐Modaf

et al. 2020

Advanced Intelligent Systems

323

224

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The compliant, continuum, and configurable robotics field in general has gained growing interest in the past years especially with the exciting advances in artificial intelligence technology, [1] which could enable various valuable applications ranging from manufacturing to safety and healthcare. [2,3] Soft robots are of notable interest because, unlike their rigid counterpart, they can easily deform while being mechanically resilient, [4,5] adapt to the outer environment without harm to humans, [6] and finally, enable low-cost manufacturing. [7] For robots to interact with the outer environment and complete tasks, a set of sensors and actuators need to be integrated into the system. Soft robots, in specific, present additional challenges because their sensing and actuation devices are generally highly integrated within the body of the robot and its whole functionality. These challenges become even more critical when the soft robot is scaled down to sub-centimeter size as the sensing, power, and data analysis units are moved off-board. As a result, miniaturized soft actuators that respond to various stimuli and show large deformations in addition to mechanical resilience are crucial. These would be particularly promising for application in artificial muscles, microrobots, and micro-manipulators. [8-10] Active and soft materials are promising for this task as they can be actuated through various external stimuli, such as photons, thermal, magnetic and/or electric field. Such materials range from particles, to polymers (either electroactive or shape memory), papers, fluids, shape memory alloys (SMAs), liquid metals, hydrogels, 2D materials, or a combination of these. [6-25] Nevertheless, some materials can be more suitable for a specific set of applications than others; for instance, materials stimulated by the near-infrared (NIR) spectrum are promising for biomedical applications, whereas sunlight-stimulated materials are suitable for nature-inspired soft robots used in outside environments. Various useful metrics are generally used to assess the performance of the actuators; these include the generated stress and strain, Young's modulus or measured stiffness, in addition to their power, work, energy, and force density. In this Review article, however, we focus on the application of the soft actuators in soft robotics where the reported metrics include mode and speed of actuation (or locomotion), power, voltage, current (of the driving signal), lifting force, and weight among others. In this Review article, different active materials that have been developed and used in soft actuators for soft robotics are discussed and grouped by the stimulus that generates the actuation response as shown in Figure 1. The physics of operation, resulting deformations, mechanical resilience, and their pros and cons are presented with a focus on the applications of the different soft

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Section: Electrodes For Soft Actuatorsmentioning

confidence: 99%

Soft Actuators for Soft Robotic Applications: A Review

El‐Atab

Mishra

Al‐Modaf

et al. 2020

Advanced Intelligent Systems

323

224

View full text Add to dashboard Cite

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“…[31] Liquid metal can also be injected to fill hollow fibers [32][33][34][35] or prepatterned microchannels. [36][37][38][39][40][41] These and other techniques are discussed in other review papers [42][43][44] and are only mentioned briefly here to highlight the fact that direct write is one of several ways to pattern liquid metals.…”

Section: Patterning Liquid Metalsmentioning

confidence: 99%

Liquid Metal Direct Write and 3D Printing: A Review

Neumann

Dickey

2020

Adv Materials Technologies

209

170

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This review discusses methods, challenges, and opportunities for direct‐write and 3D printing of low melting point, gallium‐based liquid metal alloys at room temperature. Alloys of gallium exhibit high conductivity and high stretchability making them well suited for use in soft circuitry for stretchable electronics and soft robotics. In addition, the liquid nature of the metal enables entirely new ways to pattern metals at room temperature; herein, the focus is placed on additive printing via nozzle‐based methods. Room temperature printing of liquid metals enables rapid fabrication of complex geometries (with dimensions as small as 10 µm) on a wide range of materials, such as polymers. These processes can be used to make metallic conductors for devices with self‐healing capabilities, soft/stretchable electrodes, and sensors.

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“…LM can be utilized as a stand-alone sensor in which resistance, capacitance, or inductance can be manipulated in response to a stimulus (e.g., touch or deformation). [2][3][4]113] Figure 5a,b shows a soft composite consisting of LM droplets suspended in an elastomer matrix. In this composite, the thin elastomer walls between the LM droplets can rupture under damaging mechanical impact (e.g., compression, fracture, or puncture), leading to the formation of conductive pathways (Figure 5b).…”

Section: Surface Modification Of Lm For Soft Sensorsmentioning

confidence: 99%

Surface Modification of Gallium‐Based Liquid Metals: Mechanisms and Applications in Biomedical Sensors and Soft Actuators

Kwon

Truong

Krisnadi

et al. 2020

Advanced Intelligent Systems

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This review focuses on surface modifications of liquid metal (LM). Gallium (Ga) and Ga-based LMs show the promising ability to maintain metallic properties under large mechanical strains when encapsulated inside an elastomer matrix. [1-7] This property is useful in a variety of applications, including wearable/deformable devices, sensors, and soft actuators-the focus of this special issue. There are several motives for creating soft and stretchable devices. For example, devices that are soft and flexible can make conformal contact to human skin for continuous and long-term monitoring. [8-11] Likewise, devices assembled on or within soft robots can maintain function during actuation (bending or stretching) while sensing dynamic motion. Conventional conductors in electronic systems are typically rigid (e.g., copper) and thus poorly suited for soft and stretchable devices. To address this issue, efforts have been taken to create stretchable and deformable conductors using thin metal films with special geometries [12-14] (e.g., pop-up and serpentine electrodes) on a deformable substrate or polymer composites filled with conductive nanomaterials in a stretchable matrix. [15,16] These approaches effectively render rigid materials stretchable through clever engineering of their geometry. However, due to the inherently nonstretchable nature of solid metal films or solid conductive particles, these components/inclusions would add to the overall rigidity of the composite and limit their deformability. LMs are interesting as stretchable conductors because they have metallic conductivity and deformability defined primarily by the encasing material (e.g., elastomer).

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Soft and Deformable Sensors Based on Liquid Metals

Cited by 62 publications

References 103 publications

Soft Actuators for Soft Robotic Applications: A Review

Soft Actuators for Soft Robotic Applications: A Review

Liquid Metal Direct Write and 3D Printing: A Review

Surface Modification of Gallium‐Based Liquid Metals: Mechanisms and Applications in Biomedical Sensors and Soft Actuators

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