Soft actuators by electrochemical oxidation of liquid metal surfaces

Liao, Jiahe; Majidi, Carmel

doi:10.1039/d0sm01851a

Cited by 22 publications

(84 citation statements)

References 42 publications

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“…Reproduced with permission. 57 Copyright 2021, Royal Society of Chemistry. (F) Actuation of a 3-layer stack LM artificial muscle and using a LM artificial muscle to swing the caudal fin of an untethered bionic robotic fish.…”

Section: Interfacial Tension Modulation By Electrochemical Oxidation and Reductionmentioning

confidence: 99%

“…Soft artificial muscles have been made that make use of the change in surface tension of LM. [56][57][58] As LM preferentially wets copper by alloying, two copper pads can be used to hold the droplet in place for actuation (Fig. 2E).…”

Section: Materials Advances Reviewmentioning

confidence: 99%

“…Maximum distance between the pads is B2-4 mm for a 1 mm radius LM droplet muscle, depending on its oxidation/reduction state and load force. 57 Another issue is that electrolysis of the electrolyte during electrochemical reactions causes hydrogen to be formed as an unwanted by-product. The gas generation can degrade the performance of the actuator.…”

Section: Materials Advances Reviewmentioning

confidence: 99%

“…56 The work density of such LM muscles created with 1 mm diameter droplets is B100 kJ m À3 . 57 Reducing the size of the droplets will result in a greater energy density due to an increase in the surface area to volume ratio. Note that interfacial tension scales linearly with length (L), whereas forces such as electrostatic and magnetic scale as L 2 and L 3 respectively.…”

Section: Materials Advances Reviewmentioning

confidence: 99%

“…A droplet size of 2 mm will result in a theoretical energy density of 10 3 kJm À3 , greater than dielectric elastomers and shape memory alloys. 57…”

Section: Materials Advances Reviewmentioning

confidence: 99%

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Liquid metals as soft electromechanical actuators

Cole

Tang

2022

Mater. Adv.

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Section: Interfacial Tension Modulation By Electrochemical Oxidation and Reductionmentioning

confidence: 99%

Section: Materials Advances Reviewmentioning

confidence: 99%

Section: Materials Advances Reviewmentioning

confidence: 99%

Section: Materials Advances Reviewmentioning

confidence: 99%

“…A droplet size of 2 mm will result in a theoretical energy density of 10 3 kJm À3 , greater than dielectric elastomers and shape memory alloys. 57…”

Section: Materials Advances Reviewmentioning

confidence: 99%

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Liquid metals as soft electromechanical actuators

Cole

Tang

2022

Mater. Adv.

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Liquid Metal Microdroplet‐Initiated Ultra‐Fast Polymerization of a Stimuli‐Responsive Hydrogel Composite

Zhang,

Liao,

Liu

et al. 2023

Adv Funct Materials

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Recent advances in composite hydrogels achieve material enhancement or specialized stimuli‐responsive functionalities by pairing with a functional filler. Liquid metals (LM) offer a unique combination of chemical, electrical, and mechanical properties that show great potential in hydrogel composites. Polymerization of hydrogels with LM microdroplets as initiators is a particularly interesting phenomenon that remains in its early stage of development. In this work, an LM‐hydrogel composite is introduced, in which LM microdroplets dispersed inside the hydrogel matrix have dual functions as a polymerization initiator for a polyacrylic acid‐poly vinyl alcohol (PAA/PVA) network and, once polymerized, as passive inclusion to influence its material and stimuli‐responsive characteristics. It is demonstrated that LM microdroplets enable ultra‐fast polymerization in ≈1 min, compared to several hours by conventional polymerization techniques. The results show several mechanical enhancements to the PAA/PVA hydrogels with LM‐initiated polymerization. It is found that LM ratios strongly influence stimuli‐responsive behaviors in the hydrogels, including swelling and ionic bending, where higher LM ratios are found to enhance ionic actuation performance. The dual roles of LM in this composite are analyzed using the experimental characterization results. These LM‐hydrogel composites, which are biocompatible, open up new opportunities in future soft robotics and biomedical applications.

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A Liquid Metal Artificial Muscle

et al. 2021

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Artificial muscles possess a vast potential in accelerating the development of robotics, exoskeletons, and prosthetics. Although a variety of emerging actuator technologies are reported, they suffer from several issues, such as high driving voltages, large hysteresis, and water intolerance. Here, a liquid metal artificial muscle (LMAM) is demonstrated, based on the electrochemically tunable interfacial tension of liquid metal to mimic the contraction and extension of muscles. The LMAM can work in different solutions with a wide range of pH (0–14), generating actuation strains of up to 87% at a maximum extension speed of 15 mm s−1. More importantly, the LMAM only needs a very low driving voltage of 0.5 V. The actuating components of the LMAM are completely built from liquids, which avoids mechanical fatigue and provides actuator linkages without mechanical constraints to movement. The LMAM is used for developing several proof‐of‐concept applications, including controlled displays, cargo deliveries, and reconfigurable optical reflectors. The simplicity, versatility, and efficiency of the LMAM are further demonstrated by using it to actuate the caudal fin of an untethered bionic robotic fish. The presented LMAM has the potential to extend the performance space of soft actuators for applications from engineering fields to biomedical applications.

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Soft actuators by electrochemical oxidation of liquid metal surfaces

Abstract: A muscle-inspired soft actuator is constructed from a liquid metal bridge, whose force and shape are controllable by electrochemical tuning of the surface energy using low voltages.

Cited by 22 publications

References 42 publications

Liquid metals as soft electromechanical actuators

Liquid metals as soft electromechanical actuators

Liquid Metal Microdroplet‐Initiated Ultra‐Fast Polymerization of a Stimuli‐Responsive Hydrogel Composite

A Liquid Metal Artificial Muscle

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