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Three-Dimensional Printing of Highly Conductive Carbon Nanotube Microarchitectures with Fluid Ink
Kim, Jung Hyun,Lee, Sanghyeon,Wajahat, Muhammad,Jeong, Hwakyung,Chang, Won Suk,Jeong, Hee Jin,Yang, Jong-Ryul,Kim, Ji Tae,Seol, Seung Kwon American Chemical Society 2016 ACS NANO Vol.10 No.9
<P>Moving printed electronics to three dimensions essentially requires advanced additive manufacturing techniques yielding multi functionality materials and high spatial resolution. Here, we report the meniscus-guided 3D printing of highly conductive multiwall carbon nano tube (MWNT) microarchitectures that exploit rapid solidification of a fluid ink meniscus formed by pulling a micronozzle. To achieve high-quality printing with continuous ink flow through a confined nozzle geometry, that is, without agglomeration and nozzle dogging, we design a polyvinylpyrrolidone-wrapped MWNT ink with uniform dispersion and appropriate rheological properties. The developed technique can produce various desired 3D microstructures, with a high MWNT concentration of up to 75 wt % being obtained via post-thermal treatment. Successful demonstrations of electronic components such as sensing transducers, emitters, and radio frequency inductors are also described herein. We expect that the technique presented in this study will facilitate selection of diverse materials in 3D printing and enhance the freedom of integration for advanced conceptual devices.</P>
산업 무선 센서 네트워크에서 종단 간 지연시간 감소를 위한 향상된 깊이 기반 TDMA 스케줄링 개선 기법
이화경(Hwakyung Lee),정상화(Sang-Hwa Chung),정익주(Ik-Joo Jung) 한국정보과학회 2015 정보과학회논문지 Vol.42 No.4
산업 무선 센서 네트워크는 뛰어난 성능과 신뢰성 있는 통신을 요구한다. 클러스터 구조는 네트워크를 형성하기 위해 소모되는 비용을 줄인다. 그리고 예약 기반 MAC 프로토콜은 네트워크 경쟁 기반 프로토콜에 비해 통신 성능 및 신뢰성이 더 뛰어나다. 이러한 구조를 갖춘 깊이 기반 TDMA 스케줄링 기법은 클러스터 네트워크상에서 깊이 정보에 따라 타임 슬롯을 분산적으로 각 센서 노드에 할당하는 방식이다. DB-TDMA가 깊이 기반 TDMA 스케줄링 기법 중 하나이고 확장성과 에너지 효율성을 보장한다. 하지만 분산 기법의 한계로 네트워크 전체 상황을 파악할 수 없어, 병렬 처리된 타임 슬롯 할당을 수행하기 어렵고, 충돌 문제를 완벽히 피할 수 없다. 이를 위해 본 논문은 DB-TDMA의 종단 간 지연시간을 감소시키기 위한 향상된 알고리즘을 제시한다. 그리고 제안 알고리즘을 DRAND와 DB-TDMA와 비교한다. Industrial WSNs need great performance and reliable communication. In industrial WSNs, cluster structure reduces the cost to form a network, and the reservation-based MAC is a more powerful and reliable protocol than the contention-based MAC. Depth-based TDMA assigns time slots to each sensor node in a cluster-based network and it works in a distributed manner. DB-TDMA is a type of depth-based TDMA and guarantees scalability and energy efficiency. However, it cannot allocate time slots in parallel and cannot perfectly avoid a collision because each node does not know the total network information. In this paper, we suggest an improved distributed algorithm to reduce the end-to-end delay of DB-TDMA, and the proposed algorithm is compared with DRAND and DB-TDMA.
Three-dimensional Printing of Silver Microarchitectures Using Newtonian Nanoparticle Inks
Lee, Sanghyeon,Kim, Jung Hyun,Wajahat, Muhammad,Jeong, Hwakyung,Chang, Won Suk,Cho, Sung Ho,Kim, Ji Tae,Seol, Seung Kwon American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.22
<P>Although three-dimensional (3D) printing has recently emerged as a technology to potentially bring about the next industrial revolution, the limited selection of usable materials restricts its use to simple prototyping. In particular, metallic 3D printing with submicrometer spatial resolution is essential for the realization of 3D-printed electronics. Herein, a meniscus-guided 3D printing method that exploits a low-viscosity (similar to 7 mPa.s) silver nanoparticle (AgNP) ink meniscus with Newtonian fluid characteriftics (which is compatible with conventional inkjet printers) to fabricate 3D silver microarchitectures is reported. Poly(acrylic acid)-capped AgNP ink that exhibits a continuous ink flow through a confined nozzle without aggregation is designed in this study. Guiding the ink meniscus with controlled direction and speed enables both vertical pulling and layer-by-layer processing, resulting in the creation of 3D microobjects with designed shapes other than those for simple wiring. Various highly conductive (>10(4) S.cm(-1)) 3D metallic patterns are demonstrated for applications in electronic devices. This research 18 expected to widen the range of Materials that can be employed in 3D printing technology, with the aim of moving 3D printing beyond prototyping and into real manufacturing platforms for future electronics.</P>