Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics

We report a spray deposition technique for patterning liquid metal alloys to form stretchable conductors, which can then be encapsulated in silicone elastomers via the same spraying procedure. While spraying has been used previously to deposit many materials, including liquid metals, this work focuses on quantifying the spraying process and combining it with silicones. Spraying generates liquid metal microparticles (~5 μm diameter) that pass through openings in a stencil to produce traces with high resolution (~300 µm resolution using stencils from a craft cutter) on a substrate. The spraying produces sufficient kinetic energy (~14 m/s) to distort the particles on impact, which allows them to merge together. This merging process depends on both particle size and velocity. Particles of similar size do not merge when cast as a film. Likewise, smaller particles (<1 µm) moving at the same speed do not rupture on impact either, though calculations suggest that such particles could rupture at higher velocities. The liquid metal features can be encased by spraying uncured silicone elastomer from a volatile solvent to form a conformal coating that does not disrupt the liquid metal features during spraying. Alternating layers of liquid metal and elastomer may be patterned sequentially to build multilayer devices, such as soft and stretchable sensors.

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Low-Cost Rapid Fabrication of Conformal Liquid-Metal Patterns

Applied Sciences ◽

10.3390/app9081565 ◽

2019 ◽

Vol 9 (8) ◽

pp. 1565 ◽

Cited By ~ 3

Author(s):

Elassy ◽

Akau ◽

Shiroma ◽

Seo ◽

Ohta

Keyword(s):

Liquid Metal ◽

Flexible Electronics ◽

Communication Systems ◽

Liquid Metals ◽

Low Cost ◽

Spray Coating ◽

Uv Curable ◽

Rapid Fabrication ◽

Communication Devices ◽

Stretchable Conductors

Patterned conformal conductive structures are used to realize flexible electronics for applications such as electronic skin, communication devices, and sensors. Thus, there is a demand for low-cost rapid fabrication techniques for flexible and stretchable conductors. Spray-coating of liquid metals is a prototyping method that is compatible with elastic substrates. In this work, UV-curable and polyimide masks were used to pattern sprayed liquid metal (LM). The effect of the spraying parameters on the thickness and conductivity of the LM was characterized. A minimum LM linewidth of 48 µm was achieved, along with a minimum gap width of 34 µm. A LM patch antenna and transmission line, which can potentially be used for communication systems, were demonstrated using this fabrication process.

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Gallium Oxide-Stabilized Oil in Liquid Metal Emulsions

Soft Matter ◽

10.1039/d1sm00982f ◽

2021 ◽

Author(s):

Najam Ul Hassan Shah ◽

Wilson Kong ◽

Nathan Casey ◽

Shreyas Kanetkar ◽

Robert Yue-Sheng Wang ◽

...

Keyword(s):

Energy Storage ◽

Liquid Metal ◽

Gallium Oxide ◽

Liquid Metals ◽

Soft Robotics ◽

Stretchable Electronics ◽

Thermal Interface Materials ◽

Thermal Interface ◽

Energy Storage Applications ◽

Interface Materials

Gallium based liquid metals (LM) have prospective biomedical, stretchable electronics, soft robotics, and energy storage applications, and are being widely adopted as thermal interface materials. The danger of gallium corroding...

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Fabrication of Soft and Stretchable Electronics Through Integration of Printed Silver Nanoparticles and Liquid Metal Alloy

Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies ◽

10.1115/smasis2018-8007 ◽

2018 ◽

Author(s):

Mahmoud Tavakoli ◽

Mohammad H. Malakooti ◽

Hugo Paisana ◽

Yunsik Ohm ◽

Daniel Green Marques ◽

...

Keyword(s):

Electrical Conductivity ◽

Silver Nanoparticles ◽

Liquid Metal ◽

Liquid Metals ◽

High Surface ◽

Cost Effective ◽

Stretchable Electronics ◽

Liquid Metal Alloy ◽

And Performance ◽

Complex Circuits

Liquid metal (LM) alloys such as eutectic gallium indium (EGaIn) and gallium-indium-tin (Galinstan) have been used in the fabrication of soft and stretchable electronics during the past several years. The liquid-phase and high electrical conductivity of these materials make them one of the best candidates for fabrication of deformable electronics and multifunctional material systems. While liquid metals are highly reliable for fabrication of simple circuits and stretchable microfluidic devices, their application for producing complex circuits faces fabrication challenges due to their high surface tension and surface oxidization. In this study, we propose a scalable, cost-effective, and versatile technique to print complex circuits using silver nanoparticles and transform them into stretchable electronics by incorporating eutectic gallium indium alloys to the circuit. As a result, the deposited liquid metal considerably increases the electrical conductivity and stretchability of the fabricated electronics. The reliability and performance of these stretchable conductors are demonstrated by studying their electromechanical behavior and integrating them into skin-like electronics, termed electronic tattoos.

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Advances in Materials for Soft Stretchable Conductors and Their Behavior under Mechanical Deformation

Polymers ◽

10.3390/polym12071454 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1454

Author(s):

Thao Nguyen ◽

Michelle Khine

Keyword(s):

Mechanical Stability ◽

Mechanical Deformation ◽

The Body ◽

Polymer Materials ◽

Performance Criteria ◽

Stretchable Electronics ◽

Self Healing ◽

Academic Settings ◽

Stretchable Conductors ◽

Stretchable Sensors

Soft stretchable sensors rely on polymers that not only withstand large deformations while retaining functionality but also allow for ease of application to couple with the body to capture subtle physiological signals. They have been applied towards motion detection and healthcare monitoring and can be integrated into multifunctional sensing platforms for enhanced human machine interface. Most advances in sensor development, however, have been aimed towards active materials where nearly all approaches rely on a silicone-based substrate for mechanical stability and stretchability. While silicone use has been advantageous in academic settings, conventional silicones cannot offer self-healing capability and can suffer from manufacturing limitations. This review aims to cover recent advances made in polymer materials for soft stretchable conductors. New developments in substrate materials that are compliant and stretchable but also contain self-healing properties and self-adhesive capabilities are desirable for the mechanical improvement of stretchable electronics. We focus on materials for stretchable conductors and explore how mechanical deformation impacts their performance, summarizing active and substrate materials, sensor performance criteria, and applications.

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Rupture stress of liquid metal nanoparticles and their applications in stretchable conductors and dielectrics

npj Flexible Electronics ◽

10.1038/s41528-021-00108-w ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Yang Liu ◽

Xinyi Ji ◽

Jiajie Liang

Keyword(s):

Dielectric Constant ◽

Liquid Metal ◽

Metal Nanoparticles ◽

Oxide Shell ◽

Stretchable Electronics ◽

Shore Hardness ◽

Rupture Stress ◽

Stretchable Conductors ◽

Different Diameters ◽

The Relationship

AbstractFew works had systematically investigated the relationship between the rupture stress of the oxide shell and the diameter of liquid metal nanoparticles (LMNPs). Here, we fabricated a series of elastomer/LMNPs composites, which were based on various polyurethanes with different shore hardness and LMNPs with different diameters, to systematically study the rupture stress of LMNPs. We established a reliable and guidable relationship between the stress–strain curves of elastomers with different shore hardness and rupture stress of LMNPs with various diameters by both experiments and numerical calculations. Based on this guidance, we can facilely prepare stretchable conductors with remarkable stretchability and conductivity (i.e., 24,130 S · cm−1 at 500% strain) and stretchable dielectrics with excellent stretchability and permittivity (i.e., dielectric constant of 76.8 with 580% strain) through controlling the shore hardness of elastomers and diameter of LMNPs. This work will facilitate the systematic study of LMNPs and expand their use in stretchable electronics.

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Kinetic Aerosol Spray Deposition of BiVO4 Powder for OER Photoelectrodes

10.29363/nanoge.ngfm.2019.084 ◽

2019 ◽

Author(s):

Thomas Emmler ◽

Charline Wolpert ◽

Mauricio Schieda ◽

Maria T. Villa Vidaller ◽

Stefen Fengler ◽

...

Keyword(s):

Spray Deposition ◽

Aerosol Spray

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Liquid metal-based nanocomposite materials: Fabrication technology and applications

Nanoscale ◽

10.1039/d0nr07479a ◽

2021 ◽

Author(s):

Hiroki Ota ◽

Nyamjargal Ochirkhuyag ◽

Ryosuke Matsuda ◽

Zihao Song ◽

Fumika Nakamura ◽

...

Keyword(s):

Liquid Metal ◽

Flexible Electronics ◽

Liquid Metals ◽

Nanocomposite Materials ◽

Fabrication Technology

Research on liquid metals has been steadily garnering more interest in recent times because the properties of these metals are conducive to flexible electronics applications; further, these metals are in...

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