Novel insights into the design of stretchable electrical systems

Martin-Monier, Louis; Piveteau, Pierre-Luc; Sorin, Fabien

doi:10.1126/sciadv.abf7558

Cited by 3 publications

(4 citation statements)

References 32 publications

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“…Eutectic gallium–indium alloy (E-GaIn: Ga 75.5%/In 24.5%, ≥99.99% trace metals; Sigma-Aldrich, St. Louis, MO, USA) was used as the liquid metal to form the conductive part. The resistivity of E-GaIn is 2.9 × 10 −7 Ω·m [ 30 ]. With a melting point of 15.5 °C, this alloy is a liquid at room temperature and has no mechanical deformation limits.…”

Section: Methodsmentioning

confidence: 99%

Stretchable Strain Sensor with Small but Sufficient Adhesion to Skin

Nishikawa

Yamane

Matsuhisa

et al. 2023

Sensors

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Stretchable strain sensors that use a liquid metal (eutectic gallium–indium alloy; E-GaIn) and flexible silicone rubber (Ecoflex) as the support and adhesive layers, respectively, are demonstrated. The flexibility of Ecoflex and the deformability of E-GaIn enable the sensors to be stretched by 100%. Ecoflex gel has sufficiently large adhesion force to skin, even though the adhesion force is smaller than that for commercially available adhesives. This enables the sensor to be used for non-invasive monitoring of human motion. The mechanical and electrical properties of the sensor are experimentally evaluated. The effectiveness of the proposed sensors is demonstrated by monitoring joint movements, facial expressions, and respiration.

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Section: Methodsmentioning

confidence: 99%

Stretchable Strain Sensor with Small but Sufficient Adhesion to Skin

Nishikawa

Yamane

Matsuhisa

et al. 2023

Sensors

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“…Several studies have reported nearly invariant resistances using networks of LM. [21,24,26,[35][36][37][38] A few theories could explain the near constant conductivity. For example, (1) particle deformation in the x-axis is compensated by particles that come closer in y-axis due to the Poisson effect.…”

Section: Stretchable Lmp Electrodementioning

confidence: 99%

“…For example, (1) particle deformation in the x-axis is compensated by particles that come closer in y-axis due to the Poisson effect. [35,37] (2) The LMP network with connected micro-and nanostructures resembles a Kirigami-like unit with 'hinges' that straighten during elongation. Thus, the conductive path itself does not change despite the substrate elongating.…”

Section: Stretchable Lmp Electrodementioning

confidence: 99%

Stretchable Liquid Metal Films with High Surface Area and Strain Invariant Resistance

Vallem

Aggarwal

Dickey

2022

Adv Materials Technologies

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In this work, we sought to create stretchable LM electrodes with high surface area, but ended up observing an additional useful property: strain-invariant resistance. Electrodes with high surface area are useful for capacitors, [15] sensors, [16] and certain energy-harvesting devices. [17] Due to surface tension, liquids naturally form spherical or hemispherical shapes, which minimize both surface energy and surface area. Gallium-based liquid metals form a native oxide 'skin' that allows LM to be shaped and patterned into nonspherical shapes. For example, LM can be stencil printed, 3D printed, or injected into microfluidic channels to form nonspherical shapes. [18] Although these approaches increase the surface area per volume of the metal relative to a sphere, they only do so modestly.The area of LM can be drastically increased by breaking it into small droplets (the diameter of which depends on the conditions, but sizes can range from 10 nm to hundreds of microns). [19] The presence of this native oxide skin on the surface allows for the formation of stable liquid metal particles that do not spontaneously coalesce or merge together when the diameters of the particles are sufficiently small. Consequently, this oxide layer causes films of liquid metal particles (LMPs) to be electrically insulating. Yet, removing the oxide layer would cause the particles to coalesce into larger droplets. Thus, it is challenging to create high surface area, conductive liquid metal films.Several approaches have been reported in the literature to percolate droplets of liquid metal within a film to create conductive pathways. Perhaps the simplest approach is to 'mechanically sinter' the particles, which involves physically pressing films of droplets together. [20] Mechanical sintering can be applied to encased [1] or exposed [20] films of particles or to particles dispersed in elastomer [21] (so-called liquid metal elastomers). Peeling films of liquid metal elastomers can also generate sufficient stress to percolate particles. [22] Particles can also be percolated using laser heating [1,23] by capillary forces, [24] or by using dielectrophoretic forces. [25] Particles covalently linked together can sinter when placed on a stretchable substrate; the stress from elongation causes the particles to rupture and merge. [26] Several of these approaches result in percolated conductors with resistance that is nearly invariant with strain.Inspired by this prior work, [26] we speculated that we might achieve a similar result by placing particles without any covalent linkages onto a tacky, stretchable substrate, and utilize This paper reports soft and stretchable films of liquid metal particles (LMPs) that offer high surface area and high conductivity. Liquid metals (LM) based on gallium are compelling conductors for soft and stretchable devices, yet it is difficult to make electrodes of LM with high surface area due to the tendency of liquids to minimize their surface area. To form films of percolated particles with high surface area, LMPs are f...

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“…However, electronic materials which are used as resistors should be strain-resistant; thus, resistance changes should be minimized. Louis et al [ 37 ] demonstrated photolithography on different structures on PDMS so that the liquid metal filled in them forms a conductive pathway, which is a novel method for multi-application electronic materials. Through reasonable structural design, the desired strain response can be obtained.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical Wrinkles for Tunable Strain Sensing Based on Programmable, Anisotropic, and Patterned Graphene Hybrids

Chu

Gong

et al. 2022

Polymers

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Flexible, stretchable, wearable, and stable electronic materials are widely studied, owing to their applications in wearable devices and the Internet of Things. Because of the demands for both strain-insensitive resistors and high gauge factor (GF) strain-sensitive materials, anisotropic strain sensitivity has been an important aspect of electronic materials. In addition, the materials should have adjustable strain sensitivities. In this work, such properties are demonstrated in reduced graphene oxide (RGO) with hierarchical oriented wrinkle microstructures, generated using the two-step shrinkage of a rubber substrate. The GF values range from 0.15 to 28.32 at 100% strain. For device demonstrations, macrostructure patterns are designed to prepare patterned wrinkling graphene at rubber substrate (PWG@R). Serpentiform curves can be used for the constant-value resistor, combined with the first-grade wrinkles. Strip lines can increase the strain-sensing property, along with the second-grade wrinkles. The patterned sensor exhibits improved GF values range from 0.05 to 49.5. The assembled sensor shows an excellent stability (>99% retention after 600 cycles) with a high GF (49.5). It can monitor the vital signs of the throat and wrist and sense large motions of fingers. Thus, PWG@R-based strain sensors have great potential in various health or motion monitoring fields.

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Novel insights into the design of stretchable electrical systems

Cited by 3 publications

References 32 publications

Stretchable Strain Sensor with Small but Sufficient Adhesion to Skin

Stretchable Strain Sensor with Small but Sufficient Adhesion to Skin

Stretchable Liquid Metal Films with High Surface Area and Strain Invariant Resistance

Hierarchical Wrinkles for Tunable Strain Sensing Based on Programmable, Anisotropic, and Patterned Graphene Hybrids

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