In Situ Alloying of Thermally Conductive Polymer Composites by Combining Liquid and Solid Metal Microadditives

Ralphs, Matthew; Kemme, Nicholas; Vartak, Prathamesh B.; Joseph, Emil; Tipnis, Sujal; Turnage, S.; Solanki, Kiran; Wang, Robert Y.; Rykaczewski, Konrad

doi:10.1021/acsami.7b15814

Cited by 111 publications

(109 citation statements)

References 67 publications

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“…Copper (often used in component pins with a thin layer of tin or gold finish) and aluminum are commonly used in IC components. Gallium and its alloys are known to significantly corrode Al through intergranular diffusion, and can alloy with and diffuse into Cu . One concern with bringing LM into direct contact with component pins is how this interfacing may affect the lifetime of the IC components.…”

Section: Resultsmentioning

confidence: 99%

EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

Özütemiz

Wissman

Özdoğanlar

et al. 2018

Adv Materials Inter

183

167

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provide increased robustness and better mechanical impedance matching with the host material or structure. For instance, they can be integrated into clothing or mounted on the skin without constraining natural body motion or causing discomfort. A promising approach for realizing stretchable electronics is to create microfluidic traces of liquid-metal (LM) embedded in a soft elastomer. [1][2][3] Ga-based LM circuits offer attractive advantages over alternative approaches. Stretchable electronics based on soft-elastomers embedded with percolating networks of rigid metallic particles, [4,5] carbon allotropes, [6,7] or conductive polymers [8,9] typically suffer from low conductivity (three orders of magnitude lower than metals) or poor electromechanical properties. Micro/nanoscale geometries of thin conductive elements (e.g., serpentine and "wavy" electronics) represent a promising alternative that achieves stretchable functionality through flexure or twisting on a prestrained elastomer substrates. [10][11][12][13][14] However, obtaining stretchability with deterministic architectures requires conductive traces to be patterned into specific geometries (e.g., prebuckled waves, planar serpentines) that are only deformable in prescribed directions. By contrast, Ga-based LM alloys, such as eutectic Ga-In (EGaIn; 75% Ga and 25% In, by weight) and Ga-In-Sn (Galinstan; 68% Ga, 22% In, 10% Sn), can be incorporated into elastomers and preserve their elastic properties at all length scales and in all loading conditions without requiring specialized geometries. [15] These alloys provide high electrical conductivity (3.4 × 10 6 S m −1 ), low melting point (−19 °C for Galinstan, 15 °C for EGaIn), low viscosity (2 mPa s), low toxicity, [16] and negligible vapor pressure. [3,15] Since they are liquid at room temperature and have metallic conductivity, EGaIn and Galinstan can function as intrinsically stretchable and deformable conductors that are not subject to the limitations of conductive polymers or deterministic architectures. As such, LM-based electronics can provide a unique combination of metallic conductivity and elastomeric deformability. Although this promise of LM-based electronics has been well recognized in recent literature, [17] advances in scalable fabrication approaches and effective electrical interfaces between liquid metal traces and microelectronics are still needed to create functional and practical soft and stretchable electronics.Eutectic gallium-indium (EGaIn) has attracted significant attention in recent years for its use in soft and stretchable electronics. However, advances in scalable fabrication approaches and effective electromechanical interfaces between liquid metal (LM) traces and microelectronics are still needed to create functional soft and stretchable electronics. In this study, EGaIn-metal interfacing for the effective integration of surface-mount microelectronics with LM interconnects is investigated. The electrical interconnects are produced by creating copper patterns on a soft-elastomer su...

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Section: Resultsmentioning

confidence: 99%

EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

Özütemiz

Wissman

Özdoğanlar

et al. 2018

Adv Materials Inter

183

167

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“…Otherwise, the polymer matrix will wet the self‐passivating Ga oxide that covers the coated particles and no decrease in thermal resistance will be evident between nickel particles. The importance of these material processing characteristics is described in our prior work, in which we used LM‐coated copper particles in a three‐phase polymer composite and leveraged the unique, rapid alloying of copper and gallium to enhance percolation through the polymer matrix . The use of magnetic alignment allows for achieving percolation at much lower filler volume ratios and significantly increases repeatability of the results.…”

Section: Resultsmentioning

confidence: 99%

“…The direct contact between particles in these percolating networks decreases the interfacial thermal boundary resistance ( R b ). This boundary resistance—also referred to as Kapitza resistance—is widely responsible for the diminishing returns seen in k c when increasing k p (e.g., a k p increase from 20 to 400 W m −1 K −1 with φ = 0.5 improves k c by only 25%) . Note that, while R c and R b are both resistances due to interfaces, these two parameters differ from one another.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Ralphs

Kong

Wang

et al. 2019

Adv Materials Inter

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Despite major advancements in the performance of thermal interface materials (TIMs), contact resistance between components persists as a major thermal bottleneck in electronics packaging. In this work, the thermal performance of composite TIMs is enhanced through a synergistic coupling of magnetic alignment and engineered particle coatings that reduce the thermal resistance between particles. By itself, magnetically induced percolation of nickel particles within a cross‐linked silicone matrix doubles the thermal conductivity of the composite. This process significantly increases contact between particles, making the interfacial particle–particle resistance a major contributor to the composites thermal performance. The resistance at these interfaces can be reduced by introducing soft metal (silver) or liquid metal coatings onto the nickel particles. Compressing powder beds of these hybrid particles reveals that, dependent on coating thickness, the contact engineering approach provides multifold increases in thermal conductivity at mild pressures. When dispersed in a polymer matrix and magnetically aligned, the coated particles provide a threefold increase in composite thermal conductivity, as compared to unaligned samples (up to nearly 6 W m−1 K−1 with volumetric fill fraction of 0.5). For equivalent coating thicknesses, silver coatings achieve better performance than liquid metal coatings.

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“…Discretization of interfaces can allow for more efficient transport, which when coupled with multifunctional structures with advanced thermal or transport properties, [205][206][207] can provide synergistic effects. As mentioned, heat transport and diffusion are fundamental limitations for thermal and fluidic-based triggers, respectively.…”

Section: Discussionmentioning

confidence: 99%

Switchable Adhesives for Multifunctional Interfaces

Croll

Hosseini

Bartlett

2019

Adv Materials Technologies

132

107

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The reliable bonding or attachment of materials is critical in many industries, is a common necessity of daily life, and is key to functionality in numerous biological settings. [1][2][3][4][5][6][7][8][9][10][11] Adhesives Joining two materials with an adhesive is an extremely common activity, but is most often irreversible. However, emerging and current applications ranging from consumer and medical products to soft robotics and wearable bio-monitoring devices demand strong adhesives which can be easily removed on-demand and subsequently reused. This requires new paradigms in adhesive science and engineering, resulting in the emergence of new classes of multifunctional switchable adhesives. Here summarized is the current state of the art in switchable adhesive systems, focusing on how devices fit into the basic science of adhesion while providing performance metrics for comparison across current approaches. Using fracture mechanics as a guide, systems are classified as functioning under one of three basic mechanisms: near-interface, contact area, or mechanical. These mechanisms must be initiated or "triggered" by a specific input, which can include mechanical, electromagnetic, fluidic, or thermal stimuli. Triggers and adhesion switching performance are compared through the use of a "switching ratio," the interfacial energy release rate, and an estimate of mechanism timing. Finally, it is discussed that how the fundamental mechanisms relate to challenges and opportunities for switchable interfaces in future applications and adhesive systems.

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In Situ Alloying of Thermally Conductive Polymer Composites by Combining Liquid and Solid Metal Microadditives

Cited by 111 publications

References 67 publications

EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Switchable Adhesives for Multifunctional Interfaces

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