Reconfigurable liquid metal circuits by Laplace pressure shaping

Cumby, B.; Hayes, Gerard J.; Dickey, Michael D.; Justice, Ryan S.; Tabor, Christopher E.; Heikenfeld, Jason

doi:10.1063/1.4764020

Cited by 96 publications

(77 citation statements)

References 22 publications

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“…This capability enables previously unidentified types of electrohydrodynamic phenomena to manipulate the shape of metal, which is attractive for a wide range of applications including microelectromechanical systems (MEMS) switches and conductive microcomponents (35), microactuators and pumps (36), adaptive electronic skins (37), tunable antennas and apertures (38,39), fluidic optical components and displays (40,41), field-programmable circuits (42), and metamaterials with reversible cloaking. The necessity of electrolyte and the reliance on electrochemical reactions may present some practical limitations for long-term switchability, although batteries operate with similar restrictions.…”

mentioning

confidence: 99%

Giant and switchable surface activity of liquid metal via surface oxidation

Khan¹,

Eaker²,

Bowden

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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345

381

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We present a method to control the interfacial tension of a liquid alloy of gallium via electrochemical deposition (or removal) of the oxide layer on its surface. In sharp contrast with conventional surfactants, this method provides unprecedented lowering of surface tension (∼500 mJ/m 2 to near zero) using very low voltage, and the change is completely reversible. This dramatic change in the interfacial tension enables a variety of electrohydrodynamic phenomena. The ability to manipulate the interfacial properties of the metal promises rich opportunities in shape-reconfigurable metallic components in electronic, electromagnetic, and microfluidic devices without the use of toxic mercury. This work suggests that the wetting properties of surface oxides-which are ubiquitous on most metals and semiconductors-are intrinsic "surfactants." The inherent asymmetric nature of the surface coupled with the ability to actively manipulate its energetics is expected to have important applications in electrohydrodynamics, composites, and melt processing of oxideforming materials.EGaIn | electrocapillarity | electrorheology | dewetting | spreading T he ability to control interfacial energy is an effective approach for manipulating fluids at submillimeter length scales due to the dominance of these forces at these small length scales and can be accomplished using a wide variety of methods including temperature (1, 2), light (3), surface chemistry (4-6), or electrostatics (7). These techniques are effective for many organic and aqueous solutions, but they have limited utility for manipulating high interfacial tension liquids, such as liquid metals. Liquid metals offer new opportunities for soft, stretchable, and shape-reconfigurable electronic and electromagnetic components (8-12). Although it is possible to mechanically manipulate these fluids at submillimeter length scales (13), electrical methods (14, 15) are preferable due to the ease of miniaturization, control, and integration. Existing electrohydrodynamic techniques can modestly tune the interfacial tension of metals but either limit the shape of liquid metals to plugs (e.g., continuous electrowetting) (16) or necessitate excessive potentials to achieve actuation on a limited scale (e.g., electrowetting) (17). Here, we demonstrate that the surface oxide on a liquid metal can be formed or removed in situ using low voltages (<1 V) and behaves like a surfactant that can significantly lower its interfacial tension from ∼500 mJ/m 2 to near zero. In contrast, conventional molecular surfactants effect only modest changes in interfacial tension (changes of ∼20-50 mJ/m 2 ) and are difficult to remove rapidly on demand (18). Our approach relies on the electrical control of surface oxidation, which is simple, requires minimal energy, and provides rapid and reversible control of interfacial tension over an enormous range, independent of the properties of the substrate upon which it rests. Furthermore, this method avoids the use of toxic mercury and the ensuing modulation of surface ten...

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mentioning

confidence: 99%

Giant and switchable surface activity of liquid metal via surface oxidation

Khan¹,

Eaker²,

Bowden

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

345

381

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“…By leveraging these unique characteristics, researchers have recently demonstrated advances in reconfigurable, responsive, and stretchable electronic devices. [5][6][7][8] Select applications of liquid metals include soft electronic skins, [9,10] dynamic and flexible antennas, [11][12][13][14] and self-healing and elastic electronics. [15,16] Moreover, the fluid nature of GaLMAs such as eutectic gallium-indium (eGaIn) enables broad process compatibility with additive printing methods such as direct write, inkjet, transfer, and 3D printing.…”

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confidence: 99%

Wiring up Liquid Metal: Stable and Robust Electrical Contacts Enabled by Printable Graphene Inks

Secor

Cook

Tabor

et al. 2017

Adv Elect Materials

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electronic materials. By leveraging these unique characteristics, researchers have recently demonstrated advances in reconfigurable, responsive, and stretchable electronic devices. [5][6][7][8] Select applications of liquid metals include soft electronic skins, [9,10] dynamic and flexible antennas, [11][12][13][14] and self-healing and elastic electronics. [15,16] Moreover, the fluid nature of GaLMAs such as eutectic gallium-indium (eGaIn) enables broad process compatibility with additive printing methods such as direct write, inkjet, transfer, and 3D printing. [17][18][19][20][21][22][23] As such, research toward the control and integration of GaLMAs for printed, stretchable, and reconfigurable electronics has attracted broad scientific and practical interest.Despite their promise, the development of liquid metal electronics must overcome several challenges for widespread application. In particular, stable electrical contacts have been identified as a critical challenge for the integration of GaLMAs in electronic circuits and systems. [4] Since gallium alloys rapidly with most metals, GaLMAs lead to unstable or mechanically sensitive interfaces when combined with metal electrodes or interconnects, thereby preventing the reliable integration of eGaIn functionality with conventional electronics. In a recent dramatic demonstration of this effect, Dickey and coworkers exploited the aggressive alloying of eGaIn with silver to direct the motion of liquid metal droplets across a surface, completely removing the silver in the process. [24] Therefore, to enable broader application of eGaIn with conventional circuits, interfacial alloying needs to be suppressed without compromising electrical or mechanical properties.Here, we demonstrate printed graphene as a reliable and high-performance interfacial layer to enable electrical connections to eGaIn. In contrast to conventional metals, sp 2 -bonded carbon materials are stable to alloy formation with liquid metals. [25,26] To leverage this property in a platform that is suitable for printed GaLMAs, graphene inks based on cellulose derivatives are used for robust contacts to liquid metal. This class of graphene inks has shown broad process compatibility with excellent electrical conductivity, mechanical durability, and environmental stability. [27][28][29][30] A thin film (≈100 nm) of fewlayer graphene flakes printed between conventional silver leads and eGaIn acts as a physical barrier, effectively passivating the surface against alloying while retaining the ability to conduct current across the interface. Moreover, graphene interfacial Gallium-based liquid metal alloys (GaLMAs) are a unique class of advanced materials with the potential to offer unprecedented opportunities in stretchable and reconfigurable electronics. Despite their promise, the development of liquid metal electronics must overcome several challenges for widespread application. In particular, stable electrical contacts have been identified as a critical challenge for the integration of GaLMAs in electronic...

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“…In Cumby, et al, 46 reconfigurable circuits were demonstrated using mercury. However, transferability of these results to non-toxic gallium-alloys is challenging due to the adhesive nature of gallium-oxide.…”

Section: Controlled Wettingmentioning

confidence: 98%

Soft electronics for soft robotics

Kramer

2015

SPIE Proceedings

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As advanced as modern machines are, the building blocks have changed little since the industrial revolution, leading to rigid, bulky, and complex devices. Future machines will include electromechanical systems that are soft and elastically deformable, lending them to applications such as soft robotics, wearable/implantable devices, sensory skins, and energy storage and transport systems. One key step toward the realization of soft systems is the development of stretchable electronics that remain functional even when subject to high strains. Liquid-metal traces embedded in elastic polymers present a unique opportunity to retain the function of rigid metal conductors while leveraging the deformable properties of liquid-elastomer composites. However, in order to achieve the potential benefits of liquid-metal, scalable processing and manufacturing methods must be identified.

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Reconfigurable liquid metal circuits by Laplace pressure shaping

Cited by 96 publications

References 22 publications

Giant and switchable surface activity of liquid metal via surface oxidation

Giant and switchable surface activity of liquid metal via surface oxidation

Wiring up Liquid Metal: Stable and Robust Electrical Contacts Enabled by Printable Graphene Inks

Soft electronics for soft robotics

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