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Combined 3D Printing Technologies and Material for Fabrication of Tactile Sensors
Morteza Vatani,Yanfeng Lu,Erik D. Engeberg,Jae-Won Choi 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
Recently, 3D printing technology has taken the spotlight internationally with the recognition of the importance of the manufacturing industry. Currently, there are many mature 3D printing processes and materials. However, an absence of fabrication capability of smart structures such as sensors and actuators remains. In this research, we present a hybrid manufacturing process including directprint/ cure (DPC) and projection-based stereolithography, along with printable materials for stretchable tactile sensors. The suggested DPC system consists of a robotically controlled micro-dispensing head, and a light curing module combined with projection stereolithography (PSL) retrofitted from a commercial projector. The materials developed in this research are based on a photocurable and stretchable liquid resin filled with multi-walled carbon nanotubes (MWNTs); this polymer/nanocomposite exhibits the piezoresistive property used in tactile sensing. We also used another hybrid process to develop a tactile sensor using a commercial machine to build the sensor body while a dispensing system was used to create the sensing elements. We have characterized the fabricated sensors with several experiments to detect the locations where forces are applied to the surfaces of the sensors. It is concluded that the suggested processes and materials are promising in developing accurate and reliable stretchable tactile sensors
Mostafa Vatani,Morteza Asghari,Gholamreza Vakili-Nezhaad 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.5
The stochastic global optimization methods have been extensively used in the fluid phase equilibrium calculations. Among these methods, Genetic Algorithm (GA) can be applied to calculate fitting parameters of activity coefficient models in equilibrium systems. In the present work, based on the GA method, the parameters of NRTL and Two-Suffix Margules models have been calculated for 20 ternary extraction systems containing ionic liquids. The values of the parameters of these models along with the root mean square deviations (rmsd) are reported. The obtained results, in terms of rmsd for these models are satisfactory, with the overall values of 0.0039 and 0.0195 for 169 tie-lines for NRTL and Two-Suffix Margules models, respectively.
Direct-write/cure conductive polymer nanocomposites for 3D structural electronics
Yanfeng Lu,Morteza Vatani,Jae-Won Choi 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.10
The use of direct-write (DW) in the fabrication of conductive structures offers dramatic benefits over traditional technologies in terms of low-cost, print-on-demand conformal manufacturing. This DW process can be combined with direct-cure (DC) process as one-step manufacturing of conducting elements, whereas conventional methods need a manufacturing process of conducting elements followed by a relatively long time post-curing/baking process. A hybrid technology combined with direct-write/cure (DWC) and projection microstereolithography (PμSL) is presented in this work. Carbon nanotubes (CNTs) were dispersed in a photopolymer solution to introduce conductivity. The developed PμSL was used to create 3D structures, and DWC of conductive photopolymers with CNTs was utilized to produce conductive paths. To show the capabilities of the developed system and materials, a 3D structure with embedded conductive paths was designed and fabricated. Based on the experiments, it is thought that the suggested manufacturing process and materials are promising to produce 3D structural electronics.
Yanfeng Lu,윤해룡,Morteza Vatani,김호찬,최재원 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.12
3D Molded interconnect device (MID) is referred to as a new paradigm of manufacturing electronic circuits with high design complexityby removing conventional wiring processes. Basically, manufacturing of MIDs consists of several steps: building a structure, creatingconductive traces, and pick-and-place of electrical components. A 3D structure was built in a commercial Additive manufacturing (AM)machine, and conductive wires were created using a silver paste on the 3D structure with a predetermined design of an electronic circuit. A Direct-print/cure (DPC) process was developed to draw the conductive wires on the surface and simultaneously harden the createdwires using thermal/radiation energy. This DPC system consists of a micro-dispensing device and light focusing module installed in amotorized xyz stage. Resistors were also printed using the developed DPC system and a synthesized carbon nanotube (CNT)/polymercomposite. The CNT/polymer composite was characterized through a rheology test and Thermal gravimetric analysis (TGA). The resistanceof the printed resistor can be controlled by varying its length and the width. Finally, an automobile cruise controller was fabricatedwith redesigned circuits for the suggested process and materials, which is a promising technology for building 3D MID parts.
Direct-Write of Multi-layer Tactile Sensors
Jae-Won Choi,Morteza Vatani,Erik D. Engeberg 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
Direct-write of piezoresistive photopolymers is regarded as a promising means to produce compliant tactile sensors. In this work, a multi-layer compliant tactile sensor was developed using a hybrid manufacturing process including soft molding, micro-dispensing and photopolymerization processes. The working principle of the suggested sensor is to detect changes in resistance as it is deformed. A compliant skin structure was built layer-by-layer using a soft polyurethane material to cover the piezoresistive sensing elements. These sensing elements were created from stretchable photocurable conductive carbon nanotube (CNT)/prepolymer nanocomposites, which were deposited by the micro-dispensing process within the polyurethane skin layers and cured during the molding process. The fabricated tactile sensor consists of two layers of sensing elements within the skin structure; there are eight stretchable straight wires in each layer. The wires in the second layer were orthogonally placed on top of the first layer so that the sensor can detect various external forces/motions in two dimensions. The fabricated sensor was characterized by several experiments such as position, and 2D pattern detection. Finally, it is concluded that the tactile sensor using the hybrid manufacturing method and materials is promising for various applications such as robotics, prosthetics, and wearable electronics.
Erik D. Engeberg,Morteza Vatani,Jae-Won Choi 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
A compliant tactile sensor (CTS) has been developed with two orthogonal layers of multi-walled carbon nanotubes (MWNTs) and polymer strips. This has enabled the detection of sliding motion along the surface of the sensor. This information is used to detect the motions of forces applied on the surface of the CTS. The speed of sliding motion in each direction can be updated with a resolution of 3mm in both of two perpendicular directions.
광경화성 수지와 다중벽 탄소나노튜브 혼합물을 이용한 신축성 센서 소재
우상구(S. G. Woo),Morteza Vatani,이인환(I. H. Lee),Jae Won Choi,김호찬(H. C. Kim),조해용(H. Y. Cho) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Recently, advancement of science enable robots to introduce at the many fields, along with a variety of sensors. The use of the tactile sensor has increasingly interest to the robots. The tactile sensor help robots to operate safely and sensitively by mechanical contact from external environment. In this regards, many kinds of tactile sensors were developed. However, in these sensors, electrode was used as a detector that leads to complex fabrication process. Furthermore, the use of electrode impede manufacturing of large scale tactile sensor. Moreover, to improve the performance of the sensor, it should be atteched on the curved surface. This study is on the fabrication of flexible tactile sensor using a photocureable resin and MWCNTs, which is possible to make large scale tactile sensor using direct writing as simple fabrication process. The MWCNTs are used as a conductive material, because it has excellent piezo resistance effect. The MWCNTs are mixed with photocureable polymer by ultrasonic dispersion method. The photocureable polymer has the flexiblity after curing process by ultraviolet rays. Therefore, the mixture has similar chracteristics with photocureable polymer as well as piezo resistance effect. To use the MWCNTs mixture at the flexible tactile sensor as a wire, it is dispensed by direct writing. This paper suggests conductive material and fabrication process for flexible tactile sensor.