Semi-liquid metal and adhesion-selection enabled rolling and transfer (SMART) printing: A general method towards fast fabrication of flexible electronics

Guo, Rui; Yao, Siyuan; Sun, Xuyang; Liu, Jing

doi:10.1007/s40843-018-9400-2

Cited by 78 publications

(54 citation statements)

References 47 publications

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“…[57] However, the adhesion of Ni-EGaIn could be controlled by the interfacial properties of different substrates. [58,59] Some research found that the wettability of a solid surface could be influenced by the chemical composition and morphological surface microstructures. [60] The scanning electron microscope (SEM) images in Figure 1f show that the morphological microstructures of nude mouse skin and PMA glue were quite different from each other.…”

Section: Fabrication and Adhesion Characterization Of Ni-egainmentioning

confidence: 99%

Semi‐Liquid‐Metal‐(Ni‐EGaIn)‐Based Ultraconformable Electronic Tattoo

Guo

Sun

Yao

et al. 2019

Adv Materials Technologies

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136

129

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silicon wafer, electronic skin, which is usually fabricated with mechanically compliant materials (low modulus, stretchable, and flexible) overcomes the fundamental mismatch between rigid devices and soft biological tissues. [13,14] At present, inorganic and organic electronic materials integrated with elastomeric substrates are the two popular approaches to fabricate electronic skin. Nonstretchable inorganic electronic materials, such as gold, copper, and silver, change the geometric structure to fit the stretched substrates. [15][16][17][18] It is obvious that the complicated, expensive fabrication methods, and limited stretchability of inorganic electronic materials restrict their widespread application. Alternatively, other inorganic electronic materials, such as nanoparticles [19][20][21] and carbon nanotubes, [22][23][24] are deposited on elastomer substrates to form a thin nanopath that can be extended when the substrates are stretched. With low-cost fabrication methods, such as direct printing [20,25] and transfer printing, [21] these materials have been highly successfully used to fabricate stretchable circuits, [26] sensing arrays, [27] and near field communication antennae. [21] Meanwhile, organic electronic materials, such as conductive small molecules and polymers and carbon-based conductive materials, [28] have good stretchability and their special chemical groups provide good conductivity. [29][30][31] However, the conductivities of nanoparticle layers and organic electronic materials are far lower than those of metal conductors. Thus, it is of great importance to develop new materials with both excellent conductivity and stretchability. Most electronic skin is fabricated on a flat device and subsequently transferred to skin. We suggest that the new conductive materials be directly printed onto the skin using a low-cost preparation method and be super-compliant and customizable.Liquid metal (eutectic gallium-indium, EGaIn) is an attractive conductive material that has shown significant promise for broad applications in flexible electronics. With its high electrical conductivity (EGaIn: 3.4 × 10 6 S m −1 ) [32] and excellent fluidity, [33] liquid metal has attracted great interest in many applications, such as stretchable antennae, [34,35] bioelectrodes, [36] strain sensors, [37] pressure sensors, [38] loudspeakers, [39] and soft robots. [40] Additionally, gallium is nontoxic with low vapor pressure, [41] which can be useful in an ambient environment. [42] Meanwhile, various patterning techniques of liquid metal have also been developed, such as microchannel injection, [43] atomized Because of its seamless skin interface, electronic skin has attracted increasing attention in the field of biomedical sensors and medical devices. Most electronic skins are based on organic or inorganic electronic materials. However, the low flexibility of inorganic materials and the limited conductivity of organic materials restricts their widespread use. A new approach is reported to fabricate electronic tattoos from N...

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Section: Fabrication and Adhesion Characterization Of Ni-egainmentioning

confidence: 99%

Semi‐Liquid‐Metal‐(Ni‐EGaIn)‐Based Ultraconformable Electronic Tattoo

Guo

Sun

Yao

et al. 2019

Adv Materials Technologies

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136

129

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“…However, unlike a rigid mask, a photoresist mask cannot be recycled and the process of photoetching is complex and time-consuming. Guo et al introduced toner as the mask and liquid metal could selectively adhere to area without toner [72]. A roller was applied to deposit liquid metal and the circuit could further be transferred to elastic substrate.…”

Section: Printing Technologymentioning

confidence: 99%

“…For instance, magnetism, ferromagnetic nano powders could be dispersed in liquid metal [55]. Moreover, nickel particles could be mixed with EGaIn for fast fabrication of soft electronics by direct writing or printing [70][71][72]. As shown in Figure 1B, Ni particles were wrapped by a liquid metal oxide layer after stirring for a moment.…”

mentioning

confidence: 99%

Advances in Liquid Metal-Enabled Flexible and Wearable Sensors

2020

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Sensors are core elements to directly obtain information from surrounding objects for further detecting, judging and controlling purposes. With the rapid development of soft electronics, flexible sensors have made considerable progress, and can better fit the objects to detect and, thus respond to changes more sensitively. Recently, as a newly emerging electronic ink, liquid metal is being increasingly investigated to realize various electronic elements, especially soft ones. Compared to conventional soft sensors, the introduction of liquid metal shows rather unique advantages. Due to excellent flexibility and conductivity, liquid-metal soft sensors present high enhancement in sensitivity and precision, thus producing many profound applications. So far, a series of flexible and wearable sensors based on liquid metal have been designed and tested. Their applications have also witnessed a growing exploration in biomedical areas, including health-monitoring, electronic skin, wearable devices and intelligent robots etc. This article presents a systematic review of the typical progress of liquid metal-enabled soft sensors, including material innovations, fabrication strategies, fundamental principles, representative application examples, and so on. The perspectives of liquid-metal soft sensors is finally interpreted to conclude the future challenges and opportunities.2 of 25 to monitor skin strain and muscle movement [32]. Introduction of soft sensors has greatly propelled the development of intelligent artificial skin, which provides not only aesthetic functions, but also perception of tactile sensation and temperature measurement [33,34]. They can also be applied to realize intelligent perception and control for robots [35][36][37]. Moreover, flexible sensors can tightly fit the object and maintain performance even while being stretched. In this way, they can respond to changes more sensitively and detect position and posture alteration in real time.Up to now, materials and techniques to achieve flexible sensors have been widely explored. To obtain better application output for the human body, both flexibility and biocompatibility of the substrates are required. Soft thermoplastic polymers and silicone elastomers are the most common substrates used to fabricate flexible sensors, such as polyethylene terephthalate (PET), poly urethane (PU), polydimethylsiloxane (PDMS) and Eco Flex [38]. Moreover, the sensing elements are other important parts, which are mainly made up of conductive materials, including organic and inorganic nanomaterials [39,40]. Carbon-based materials, such as carbon nanotube and graphene, have been investigated in various soft circuits [39,[41][42][43][44][45][46]. Although circuits fabricated by carbon-based materials are highly stretchable, they are not as conductive as those fabricated by metals. Nanoparticles of rigid metals are applied to design soft circuits with high conductivity, among which silver nanoparticles have been extensively studied [47][48][49][50][51][52][53]. Moreover, liquid me...

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“…This results in selective wetting of EGaIn and EGaIn‐Ni amalgams as demonstrated in refs. [ 42 ] and [ 43 ] , respectively. The current work builds over these works and improves the conductivity, printing resolution, and stretchability of the printed samples.…”

Section: Introductionmentioning

confidence: 99%

High Resolution Soft and Stretchable Circuits with PVA/Liquid‐Metal Mediated Printing

Silva

Paisana

Fernandes

et al. 2020

Adv Materials Technologies

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A novel technique that permits, for the first time, fabrication of stretchable traces with linewidths as low as 20 µm and line‐spacing of 30 µm, based on simple coating and printing techniques, performed entirely at ambient condition, is demonstrated. By relying on existing inkjet printing technique, the proposed sinter‐free method is a step toward scalable fabrication of high‐resolution stretchable circuits, with application in logic gates, transparent conductors, and solar panels. This is accomplished by coating a layer of poly(vinyl alcohol) (PVA) over an elastic substrate, inkjet printing a circuit with silver nanoparticle (AgNP) ink, and then coating the printed circuit with a thin film of eutectic gallium‐indium‐tin (Galinstan) alloy. The Galinstan coating selectively wets to the printed AgNPs, resulting in highly conductive (6.65 × 106 S m−1) circuits that can withstand over 100% of strain with a modest gauge factor of ≈2.7. The process does not need thermal sintering, thanks to the Galinstan fusion with AgNPs, thus being compatible with heat‐sensitive substrates. The PVA coating has a critical role as a hydrophilic surface that absorbs the water‐based ink but resists wetting of the Galinstan. This method is demonstrated over a variety of substrates, including ultrasoft polyurethanes, ultra‐stretchable styrene–ethylene/butylynestyrene, and polyimide.

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Semi-liquid metal and adhesion-selection enabled rolling and transfer (SMART) printing: A general method towards fast fabrication of flexible electronics

Cited by 78 publications

References 47 publications

Semi‐Liquid‐Metal‐(Ni‐EGaIn)‐Based Ultraconformable Electronic Tattoo

Semi‐Liquid‐Metal‐(Ni‐EGaIn)‐Based Ultraconformable Electronic Tattoo

Advances in Liquid Metal-Enabled Flexible and Wearable Sensors

High Resolution Soft and Stretchable Circuits with PVA/Liquid‐Metal Mediated Printing

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