3D printing of ionic conductors for high-sensitivity wearable sensors

Yin, Xiangyu; Zhang, Yue; Cai, Xiaobing; Guo, Qiuquan; Yang, Jun; Wang, Zhong Lin

doi:10.1039/c8mh01398e

Cited by 177 publications

(154 citation statements)

References 67 publications

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“…In this work, the UV wavelength is 405 nm with a power density of 20 mW cm −2 . Both the WPUA and the hydrogel precursor individuals have been proven to be precisely and effectively processed with DLP printers . However, in a dual‐material printing system, the amount of photoinitiator in the two precursors should be adjusted to make their curing times matching with each other (detailed precursors formulations are presented in the Experimental Section).…”

Section: Resultsmentioning

confidence: 99%

“…However, the resolution of the grid structure fabricated by extrusion‐based 3D printers is low (≈410 µm), so its role in increasing sensitivity is limited, which is not comparable with the state‐of‐the‐art capacitive e‐skins . We recently reported an ionic hydrogel formulation which can be processed by commercial digital light processing (DLP) 3D printers . The resolution of final printed parts is about 140 µm.…”

Section: Introductionmentioning

confidence: 99%

“…The ionic skins are fabricated by the alternating 3D printing of two photocurable precursors: hydrogel (PAAm/PEGDA/Mg 2+ ) and water‐dilutable polyurethane acrylate (WPUA), in which the hydrogel layers function as soft, transparent electrode component while the WPUA layers function as flexible, transparent dielectric component and seals to retard hydrogel dehydration as well. Our previous work has demonstrated that the ionic conductive hydrogel (PAAm/PEGDA/Mg 2+ ) can be processed by a commercial DLP printer with a high resolution (140 µm). The resulting hydrogel is ionically conductive, highly elastic, and transparent with stable electromechanical properties, which is ideal to be used as a skin‐like electrode with microstructures in wearable devices.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Monolithic Dual‐Material 3D Printing of Ionic Skins with Long‐Term Performance Stability

Yin

Zhang

Xiao

et al. 2019

Adv Funct Materials

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Artificial "ionic skin" is of great interest for mimicking the functionality of human skin, such as subtle pressure sensing. However, the development of ionic skin is hindered by the strict requirements of device integration and the need for devices with satisfactory performance. Here, a dual-material printing strategy for ionic skin fabrication to eliminate signal drift and performance degradation during long-term use is proposed, while endowing the ionic skins with high sensitivity by 3D printing of ionic hydrogel electrodes with microstructures. The ionic skins are fabricated by alternative digital light processing 3D printing of two photocurable precursors: hydrogel and water-dilutable polyurethane acrylate (WPUA), in which the ionically conductive hydrogel layers serve as soft, transparent electrodes and the electrically insulated WPUA as flexible, transparent dielectric layers. This novel dualmaterial printing strategy enables strong chemical bonding between the hydrogel and the WPUA, endowing the device with designed characteristics. The resulting device has high sensitivity, minimal hysteresis, a response time in the millisecond range, and excellent repetition durability for pressure sensing. The results demonstrate the potential of the dual-material 3D printing strategy as a pathway to realize highly stable and high-performance ionic skin fabrication to monitor human physiological signals and humanmachine interactions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monolithic Dual‐Material 3D Printing of Ionic Skins with Long‐Term Performance Stability

Yin

Zhang

Xiao

et al. 2019

Adv Funct Materials

Self Cite

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“…[66,99,119] The typical materials used for stereolithography printing are resins. [77,119,120] Functional materials such as hydrogels [121][122][123] and photocurable polydimethylsiloxane (PDMS) [124][125][126] have also been demonstrated for stereolithography printing. However, stereolithography printing has limited applications for integrated wearable devices, especially for multimaterials printing.…”

Section: Ink-based Additive Nanomanufacturing Techniquesmentioning

confidence: 99%

Ink‐Based Additive Nanomanufacturing of Functional Materials for Human‐Integrated Smart Wearables

2020

Advanced Intelligent Systems

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Human-integrated devices include wearable and implantable devices for monitoring vital human signals or interacting with the human body. [1-3] The human-integrated devices needed to be tethered to the organs or the human skin for implementing their functions such as sensing and energy harvesting. [4-18] The economical, agile, customizable manufacturing, and integration of multifunctional device modules into networked systems with mechanical compliance and robustness will enable unprecedented human-integrated smart wearables [19-23] and usher in exciting opportunities in emerging technologies such as electronics, [24-29] wearable computation, [30-36] human-machine interface, [37-42] robotics, [43-48] and advanced healthcare. [49-54] The fabrication of stateof-the-art microelectronics involves hightemperature processing steps, which are generally incompatible with the flexible substrates (e.g., paper, polymer, fiber, etc.) [55-61] widely used in the wearable devices. Moreover, the current microfabrication technologies are not well positioned to process the emerging functional nanomaterials (e.g., nanowires [NWs] and 2D materials). [62-65] Such incomparability severely limits the pace of deploying these emerging materials (despite their unprecedented properties) in wearable and flexible device technologies. The additive manufacturing (AM) processes have emerged as potential candidates for addressing the earlier limitations of the current microfabrication technologies in fabricating flexible/wearable printed devices with diversified functionalities, e.g., energy harvesting/storage, sensing, actuation, and computation, leveraging advantages such as maskless processing, versatile ink formulation, low cost, low processing temperature, and scalability. [66-71] Researchers have devoted tremendous efforts to develop the related technologies, and several reviews have provided excellent discussions on the material formulation and process aspects of AM techniques. [63,72-79] However, to our best knowledge, there are few review reports about the ink-based additive nanomanufacturing of functional materials for human-integrated smart wearables. To fill this gap, here we review the recent progress in ink-based

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“…Hydrogels, a polymeric material, whose chains have abundant hydrophilic groups for retaining a significant fraction of water, have been widely used in various fields such as soft robotics and regenerative medicine. The applications of traditional hydrogels are often severely limited by their low mechanical [1][2][3][4]. Fortunately, With the deepening of research, highly stretchable hydrogels [5], conductive hydrogels [6], 3D printable hydrogels [7] and self-healing hydrogels [8] are emerging continuously.…”

Section: Introductionmentioning

confidence: 99%

Tough and conductive polymer hydrogel based on double network for photo-curing 3D printing

Ding

Jia

Gan

et al. 2020

Mater. Res. Express

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Conductive hydrogels (CHs) have attracted significant attention in wearable equipment and soft sensors due to their high flexibility and conductivity. However, CHs with high-strength and freestructure still need to be further explored. Herein, 3D printing high-strength conductive polymer hydrogels (CPHs) based on a double network was prepared. Firstly, PHEA-PSS hydrogels were prepared by copolymerizing 2-Hydroxyethyl acrylate (HEA) with 4-Vinylbenzenesulfonic acid (SSS) using a photo-curing 3D printer. Then 3, 4-Ethylenedioxythiophene (EDOT) was in situ polymerized in the network of PHEA-PSS to obtain the PHEA-PSS/PEDOT hydrogels. It can not only satisfy the printing of complex spatial structures, but also has high mechanical and electrical properties. When the content of EDOT is 12 wt%, the tensile strength of the PHEA-PSS/PEDOT hydrogels is close to 8 MPa, the electrical conductivity reach to 1.2 S cm −1 and the elasticity remain unchanged. Due to the presence of hydrogen and coordination bonds, CPHs have certain self-heal ability. In addition, the resistance of the hydrogel is sensitive to the changes of external pressure. The results show that CPHs can be used as a 3D printing material for flexible sensors.

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3D printing of ionic conductors for high-sensitivity wearable sensors

Abstract: DLP 3D printed ionic hydrogels are designed as sensitivity-improved electrodes in a skin-like sensor.

Cited by 177 publications

References 67 publications

Monolithic Dual‐Material 3D Printing of Ionic Skins with Long‐Term Performance Stability

Monolithic Dual‐Material 3D Printing of Ionic Skins with Long‐Term Performance Stability

Ink‐Based Additive Nanomanufacturing of Functional Materials for Human‐Integrated Smart Wearables

Tough and conductive polymer hydrogel based on double network for photo-curing 3D printing

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