Stretchable conductive nanocomposites fabricated by integrating metallic nanomaterials with elastomers have become a vital component of human‐friendly electronics, such as wearable and implantable ...devices, due to their unconventional electrical and mechanical characteristics. Understanding the detailed material design and fabrication strategies to improve the conductivity and stretchability of the nanocomposites is therefore important. This Review discusses the recent technological advances toward high performance stretchable metallic nanocomposites. First, the effect of the filler material design on the conductivity is briefly discussed, followed by various nanocomposite fabrication techniques to achieve high conductivity. Methods for maintaining the initial conductivity over a long period of time are also summarized. Then, strategies on controlled percolation of nanomaterials are highlighted, followed by a discussion regarding the effects of the morphology of the nanocomposite and postfabricated 3D structures on achieving high stretchability. Finally, representative examples of applications of such nanocomposites in biointegrated electronics are provided. A brief outlook concludes this Review.
This Review covers recent advances of high‐performance stretchable metallic nanocomposite for human‐friendly device applications. It starts with material synthesis and nanocomposite fabrication techniques for achieving and preserving high conductivity. Next, strategies on controlling the percolation network and morphology of the nanocomposite for high stretchability are explained, followed by methods to post‐fabricate 3D structures. Finally, examples of human‐friendly applications are introduced.
Venous invasion is three times more common in pancreatic cancer than it is in other major cancers of the gastrointestinal tract, and venous invasion may explain why pancreatic cancer is so deadly. To ...characterize the patterns of venous invasion in pancreatic cancer, 52 thick slabs (up to 5 mm) of tissue were harvested from 52 surgically resected human ductal adenocarcinomas, cleared with a modified iDISCO method, and labeled with fluorescent-conjugated antibodies to cytokeratin 19, desmin, CD31, p53 and/or e-cadherin. Labeled three-dimensional (3D) pancreas cancer tissues were visualized with confocal laser scanning or light sheet microscopy. Multiple foci of venous and even arterial invasion were visualized. Venous invasion was detected more often in 3D (88%, 30/34 cases) than in conventional 2D slide evaluation (75%, 25/34 cases, P < 0.001). 3D visualization revealed pancreatic cancer cells crossing the walls of veins at multiple points, often at points where preexisting capillary structures bridge the blood vessels. The neoplastic cells often retained a ductal morphology (cohesive cells forming tubes) as they progressed from a stromal to intravenous location. Although immunolabeling with antibodies to e-cadherin revealed focal loss of expression at the leading edges of the cancers, the neoplastic cells within veins expressed e-cadherin and formed well-oriented glands. We conclude that venous invasion is almost universal in pancreatic cancer, suggesting that even surgically resectable PDAC has access to the venous spaces and thus the ability to disseminate widely. Furthermore, we observe that sustained epithelial-mesenchymal transition is not required for venous invasion in pancreatic cancer.
IoT (IoT) networks generate massive amounts of data while supporting various applications, where the security and protection of IoT data are very important. In particular, blockchain technology ...supporting IoT networks is considered as the most secure, expandable, and scalable database storage solution. However, existing blockchain systems have scalability problems due to low throughput and high resource consumption, and security problems due to malicious attacks. Several studies have proposed blockchain technologies that can improve the scalability or the security level, but there have been few studies that improve both at the same time. In addition, most existing studies do not consider malicious attack scenarios in the consensus process, which deteriorates the blockchain security level. In order to solve the scalability and security problems simultaneously, this paper proposes a Dueling Double Deep-Q-network with Prioritized experience replay (D3P) based secure trust-based delegated consensus blockchain (TDCB-D3P) scheme that optimizes the blockchain performance by applying deep reinforcement learning (DRL) technology. The TDCB-D3P scheme uses a trust system with a delegated consensus algorithm to ensure the security level and reduce computing costs. In addition, DRL is used to compute the optimum blockchain parameters under the dynamic network state and maximize the transactions per second (TPS) performance and security level. The simulation results show that the TDCB-D3P scheme can provide a superior TPS and resource consumption performance. Furthermore, in blockchain networks with malicious nodes, the simulation results show that the proposed scheme significantly improves the security level when compared to existing blockchain schemes by effectively reducing the influence of malicious nodes.
Stretchable metallic nanocomposites are viable material candidates for high‐performance soft biointerfacing electrodes. However, it is still challenging to fabricate a stretchable metallic ...nanocomposite that features outstanding charge transfer capability and low impedance as well as high conductivity and mechanical stability. Herein, a material strategy for a stretchable conductor that meets such requirements by integrating stretchable conductive nanocomposites with stretchable conductive nanomembranes (NMs) is presented. The silver nanowire (Ag NW) NM fabricated by the float assembly method is integrated with the Ag NW nanocomposite prepared by the drop‐casting method. The compactly assembled NWs in the NM maximize conductivity by reinforcing the percolation networks of the nanocomposite. Moreover, the NM lowers impedance by allowing efficient charge transfer to the target tissue through the exposed NWs. After their integration, a high conductivity of ≈35 700 S cm−1 is obtained, and the impedance is decreased by ≈88.9% (at 1000 Hz) in comparison with the original Ag NW‐based nanocomposite (i.e., without integration of the NM). The soft bioelectrode using the stretchable conductor successfully records electrograms from the rat heart, recognizes various arrhythmic events, and applies feedback pacing.
By integrating the silver nanowires (Ag NWs)‐based nanomembrane (NM) with the Ag NWs‐based nanocomposite (NC), a new type of high‐performance stretchable conductive nanocomposite is developed. The integration reinforces the electrical percolation networks and enlarges the effective surface area of the NC. As a result, significant improvements in material properties, such as conductivity, charge transfer capability, and surface impedance, are achieved.
Stretchable Electronics
In article number 2303458, Dae‐Hyeong Kim and co‐workers report how when a nanocomposite solution is solidified in high humidity, nanowires self‐assemble into bundles, ...resulting in a highly conductive and stretchable nanocomposite. The nanocomposite is then cut into a serpentine‐shaped wearable thermostimulation device and applied to the wrist.
Injectable hydrogels show high potential for in vivo biomedical applications owing to their distinctive mode of administration into the human body. In this study, we propose a material design ...strategy for developing a multifunctional injectable hydrogel with good adhesiveness, stretchability, and bioresorbability. Its multifunctionality, whereupon multiple reactions occur simultaneously during its injection into the body without requiring energy stimuli and/or additives, was realized through meticulous engineering of bioresorbable precursors based on hydrogel chemistry. The multifunctional injectable hydrogel can be administered through a minimally invasive procedure, form a conformal adhesive interface with the target tissue, dynamically stretch along with the organ motions with minimal mechanical constraints, and be resorbed in vivo after a specific period. Further, the incorporation of functional nanomaterials into the hydrogel allows for various in vivo diagnostic and therapeutic applications, without compromising the original multifunctionality of the hydrogel. These features are verified through theranostic case studies on representative organs, including the skin, liver, heart, and bladder.
Stretchable conductive nanocomposites have been intensively studied for wearable bioelectronics. However, development of nanocomposites that simultaneously feature metal‐like conductivity(> 100 000 S ...cm−1) and high stretchability (> 100%) for high‐performance skin‐mountable devices is still extremely challenging. Here a material strategy for such a nanocomposite is presented by using local bundling of silver nanowires stabilized with dual ligands (i.e., 1‐propanethiols and 1‐decanethiols). When the nanocomposite is solidified via solvent evaporation under a highly humid condition, the nanowires in the organic solution are bundled and stabilized. The resulting locally‐bundled nanowires lower contact resistance while maintain their percolation network, leading to high conductivity. Dual ligands of 1‐propanethiol and 1‐decanethiol further boost up the conductivity. As a result, a nanocomposite with both high conductivity of ≈122,120 S cm−1 and high stretchability of ≈200% is obtained. Such superb electrical and mechanical properties are critical for various applications in skin‐like electronics, and herein, a wearable thermo‐stimulation device is demonstrated.
A material strategy to fabricate a stretchable nanocomposite with metal‐like conductivity and high stretchability is proposed. When the nanocomposite is solidified in the highly humid air, silver nanowires are locally‐bundled, minimizing contact resistance. Treatment of dual ligands of 1‐propanethiol and 1‐decanethiol improves conductivity further to ≈120 000 S cm−1 while attaining high stretchability of ≈200% for skin‐mountable devices.
Highly conductive and stretchable nanocomposites are promising material candidates for skin electronics. However, the resistance of stretchable metallic nanocomposites highly depends on external ...strains, often deteriorating the performance of fabricated electronic devices. Here, a material strategy for the highly conductive and stretchable nanocomposites comprising metal nanomaterials of various dimensions and a viscoelastic block‐copolymer matrix is presented. The resistance of the nanocomposites can be well retained under skin deformations (<50% strain). It is demonstrated that silver nanomaterials can self‐organize inside the viscoelastic media in response to external strain when their surface is conjugated with 1‐decanethiol. Distinct self‐organization behaviors associated with nanomaterial dimensions and strain conditions are found. Adopting the optimum composition of 0D/1D/2D silver nanomaterials can render the resistance of the nanocomposites insensitive to uniaxial or biaxial strains. As a result, the resistance can be maintained with a variance of < 1% during 1000 stretching cycles under uniaxial and biaxial strains of <50% while a high conductivity of ≈31 000 S cm−1 is achieved.
A material strategy to fabricate a stretchable metallic nanocomposite with strain‐insensitive resistance is proposed. When the surface of silver nanomaterials is treated with 1‐decanethiol, the nanomaterials self‐organize in response to external strain. Adopting the optimum composition of 0D/1D/2D silver nanomaterials enables preservation of the percolation networks, resulting in strain‐insensitive resistance of the nanocompsite.
Circuit design plays an essential role in all consumer electronics products. Printed circuit board (PCB) and very-large-scale integration (VLSI) circuit designing requires optimization of the ...electronic component's placement and wire routing to connect the components. Currently, circuit routing processes have been performed manually by experts, which greatly increases the cost of human resources and time. Such heuristic circuit designs are not optimized and may have errors, which is why automated circuit routing algorithms are important. However, it is difficult to obtain an optimal solution in circuit routing as it is an NP-hard problem. In addition, poor circuit routing increases the wire length of the circuit, which causes an increase in circuit cost and weight as well as performance degradation. In order to achieve routing optimization, many technologies have been proposed, in which some have applied artificial intelligence (AI) to improve the overall performance and reduce the designing time. Accordingly, in this paper, routing problems in PCB and VLSI are explained, and proposed technologies to solve these routing problems are introduced. Especially, a detailed investigation and analysis of AI technologies grafted into circuit routing algorithms are explained, and the considerations for AI-based routing algorithms are presented.
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