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Spontaneous self-welding of silver nanowire networks
Seong, Baekhoon,Chae, Ilkyeong,Lee, Hyungdong,Nguyen, Vu Dat,Byun, Doyoung The Royal Society of Chemistry 2015 Physical chemistry chemical physics Vol.17 No.12
<P>As an alternative to the traditional indium tin oxide transparent electrode, solution-processed metal nanowire thin film has been a promising candidate due to its flexibility. However, high contact resistance between the nanowires remains a major challenge to improve the performance. Here, we have investigated a one-step process of coating and welding of nanowires on flexible film. An electric field-assisted spray coating method developed in this study could generate finely charged droplets of nanowire solution at high flow rate. While charged droplets deposited on the flexible film, electric charges were flowing through the nanowire network producing electrical current. It induced Joule heating and welding at junctions of the nanowires without post-processing steps. Using the coating method, the silver nanowire thin film could be uniformly deposited evenly on a large area substrate, and spontaneously self-welding was carried out between the nanowire networks. The transparent electrode of the silver nanowire prepared by the concurrent deposition and the self-welding process could improve uniformity, roughness and sheet resistance.</P> <P>Graphic Abstract</P><P>As an alternative to the traditional indium tin oxide transparent electrode, solution-processed metal nanowire thin film has been a promising candidate due to its flexibility. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cp00035a'> </P>
Self-Assembly of Silver Nanowire Ring Structures Driven by the Compressive Force of a Liquid Droplet
Seong, Baekhoon,Park, Hyun Sung,Chae, Ilkyeong,Lee, Hyungdong,Wang, Xiaofeng,Jang, Hyung-Seok,Jung, Jaehyuck,Lee, Changgu,Lin, Liwei,Byun, Doyoung American Chemical Society 2017 Langmuir Vol.33 No.14
<P>In a nanowire dispersed in liquid droplets, the interplay between the surface tension of the liquid and the elasticity of the nanowire determines the final morphology of the bent or buckled nanowire. Here, we investigate the fabrication of a silver nanowire ring generated as the nanowire encapsulated inside of fine droplets. We used a hybrid aerodynamic and electrostatic atomization method to ensure the generation of droplets with scalable size in the necessary regime for ring formation. We analytically calculate the compressive force of the droplet driven by surface tension as the key mechanism for the self-assembly of ring structures. Thus, for potential large-scale manufacturing, the droplet size provides a convenient parameter to control the realization of ring structures from nanowires.</P>
Seong, Baekhoon,Lee, Hyungdong,Lee, Jaehyun,Lin, Liwei,Jang, Hyung-Seok,Byun, Doyoung American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.30
<P>Organic-inorganic hybrid layer-by-layer (LBL) composite structures can not only increase the strength and ductility of materials but also well disperse nanomaterials for better-conducting pathways. Here, we discovered the self-assembly process of an organic and silver (Ag) LBL hybrid structure having excellent sustainability during the long-term bending cycle. During the assembly process, the organic and Ag hybrid structure can be self-assembled into a layered structure. Unlike other conventional LBL fabrication processes, we applied the hydrogel scaffold of a biological polymer, which can spontaneously phase separate into an LBL structure in a water/alcohol solvent system. This new hydrogel-based Ag LBL patterns can successfully be printed on a flexible polyimide film without nozzle-clogging problem. Although these Ag LBL patterns cracked during the bending cycle, carbonized organic compounds between the Ag layers help to self-heal within few minutes at a low temperature (<80 °C). On the basis of our new hydrogel-based Ag ink, we could fabricate a fully printed reliable microscale flexible heater. We expect that our self-layering phenomenon can expand to the broad research field of flexible electronics in the near future.</P> [FIG OMISSION]</BR>
Zhang, Bin,Seong, Baekhoon,Lee, Jaehyun,Nguyen, VuDat,Cho, Daehyun,Byun, Doyoung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.35
<P>A one-step sub-micrometer-scale electrohydrodynamic (EHD) inkjet three-dirnensional (3D)-printing technique that is based on the drop-on demand (DOD) operation for which an additional postsintering process is not required is proposed. Both the numerical simulation and the experimental observations proved that nanoscale Joule heating Occurs at the interface between the charged silver nanoparticles (Ag-NPs) because of the high electrical contact resistance during the printing process; this is the reason why an additional postSintering process is not required. Sub-micrometer-scale 3D structures were printed with an above-35 aspect ratio via the use of the proposed printing technique; furthermore, it is evident that the designed 3D structures such as a bridge-like shape can be printed with the use of the proposed printing technique, allowing for the cost-effective fabrication of a 3D touch sensor and an ultrasensitive tihict air flow-rate sensor. It is believed that the proposed one-step printing technique May replace the conventional 3D conductive-structure printing techniques for which a postsintering, process is used 'because of its economic efficiency.</P>
Zhang, Bin,Seong, Baekhoon,Nguyen, VuDat,Byun, Doyoung IOP 2016 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.26 No.2
<P>Recently, the three-dimensional (3D) printing technique has received much attention for shape forming and manufacturing. The fused deposition modeling (FDM) printer is one of the various 3D printers available and has become widely used due to its simplicity, low-cost, and easy operation. However, the FDM technique has a limitation whereby its patterning resolution is too low at around 200 <I>μ</I>m. In this paper, we first present a hybrid mechanism of electrohydrodynamic jet printing with the FDM technique, which we name E-FDM. We then develop a novel high-resolution 3D printer based on the E-FDM process. To determine the optimal condition for structuring, we also investigated the effect of several printing parameters, such as temperature, applied voltage, working height, printing speed, flow-rate, and acceleration on the patterning results. This method was capable of fabricating both high resolution 2D and 3D structures with the use of polylactic acid (PLA). PLA has been used to fabricate scaffold structures for tissue engineering, which has different hierarchical structure sizes. The fabrication speed was up to 40 mm/s and the pattern resolution could be improved to 10 <I>μ</I>m.</P>