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Small Electrical Nerve Stimulator by Arm Processor
Sanghyo Woo,Changwook Kim,Mohyuddin Zia,Sangheon Lee,Euisung Chung,Jangwoo Lee,Junghyun Lee,Heejoon Park,Chulho Won,Jinho Cho 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
Recently, performance of a mobile phone has increased dramatically, and it is possible to integrate various biotechnologies into the mobile phone. Among the various biotechnologies, a transcutaneous electrical nerve stimulator has many advantages such as improve the circulation of blood and suppress a pain. To integrate the stimulator in the mobile phone, it is necessity to make small, low power, and safe module. In this paper, the transcutaneous electrical nerve stimulation module was designed and implemented by small boost converter. To reduce the power consumption, the external ADC was used to measure the value of the charged energy. Also, the module limits the maximum transmit power by tank capacitor value to inprove safety. To confirm the operation of designed module, an arm processor was used to control the module. The implemented module consumes only 6.6 ㎽ (without CPU) at normal stimulus mode.
Hong, John,Lee, Young-Woo,Ahn, Docheon,Pak, Sangyeon,Lee, Juwon,Jang, A-Rang,Lee, Sanghyo,Hou, Bo,Cho, Yuljae,Morris, Stephen M.,Shin, Hyeon Suk,Cha, SeungNam,Sohn, Jung Inn,Kim, Jong Min Elsevier 2017 Nano energy Vol.39 No.-
<P><B>Abstract</B></P> <P>Designing and tailoring the assembly of complex ternary transition metal oxide (TTMO) structures are a key step in the pursuit of high performance pseudo-capacitive materials for the development of next-generation energy storage devices. Here, we present uniquely assembled 3D porous heterostructures with hierarchically-coordinated TTMOs, comprising the multiply interconnected primary nanoporous frameworks of ZnCo<SUB>2</SUB>O<SUB>4</SUB>/NiMoO<SUB>4</SUB> core-shell structures and the secondary protruding structures of NiMoO<SUB>4</SUB> layered nanosheets. By benefiting from the combination of hierarchically cooperative two TTMOs, the developed 3D ZnCo<SUB>2</SUB>O<SUB>4</SUB>/NiMoO<SUB>4</SUB> heterostructures with their stable, porous, and conductive features exhibit robust pseudo-capacitive performance with high capacitances of 6.07Fcm<SUP>–2</SUP> and 1480.48Fg<SUP>–1</SUP> at 2mAcm<SUP>–2</SUP> as well as an excellent cycling stability of 90.6% over 15,000 cycles. Moreover, an asymmetric supercapacitor device can deliver a high energy density of 48.6Whkg<SUP>–1</SUP> and a power density of 2820Wkg<SUP>–1</SUP>. The superior pseudo-capacitive energy storage characteristics are strongly attributed to the interconnected 3D nanoporous network architectures of the TTMOs along with the secondary layered nanosheets that provide 1) the enlarged surface area with the high conductivity, 2) the facile and multi-access ion paths, and 3) the favorable structural stability. Combined, these results highlight the importance of novel nanostructure design in maximizing the pseudo-capacitive performance and provide a viable way to develop new electrode materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A hierarchically-coordinated two TTMOs based heterostructures were proposed and synthesized. </LI> <LI> The TTMOs showed multiple interconnected nanoporous architecture and protruding nanosheets. </LI> <LI> The resultant electrode exhibited high capacitance with ultra-high cyclability. </LI> <LI> The full cell demonstrated superior energy and power densities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Cho, Yuljae,Lee, Sanghyo,Hong, John,Pak, Sangyeon,Hou, Bo,Lee, Young-Woo,Jang, Jae Eun,Im, Hyunsik,Sohn, Jung Inn,Cha, SeungNam,Kim, Jong Min The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.26
<P>Realization of self-powered sensor systems is the key to accomplish internet of things technology for smart life of humans. Recent advances in energy harvesting using photovoltaic and triboelectric effects demonstrate outstanding performances of energy harvesters as power supplies. However, there are still fundamental issues that need to be thoroughly dealt with, which have been neglected so far, such as power interruption due to intermittence of environmental energy and long-term device stability in air. In this report, we demonstrate a hybrid energy harvester (HEH) that is composed of high air stable quantum dots solar cells (QDSCs) and a triboelectric nanogenerator (TENG). The HEH demonstrates dual mode as well as simultaneous energy harvesting with respect to types of energy present. Attributed to high photocurrent and high potential from QDSCs and the TENG, immediate base power followed by steady enhancement in power generation is achieved in this hybrid system. The HEH demonstrates as a stable power supply to accomplish a sustainable sensor system without the aid of any external power supply.</P>
Polysomnography by ECG Telemetry System
Mohy-Ud-Din Zia,Woo Sanghyo,Changwook Kim,Junghyun Lee,Jangwoo Lee,Heejoon Park,Chulho Won,Euisung Chung,J. H. Cho 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
Recently, the biotelemetry is become more and more popular and people and trying to get the maximum beneficent from it. In this regard we developed real ECG telemetry system have extremely low power consumption and the dimensions are 2.5 ㎝ by 3 ㎝. In this circuit ECG amplifier and transmitter are embedded on the single side PCB. This paper explain the method to use the 2-lead ECG signal in the recording of the dream time of a normal person by detecting the REM sleep time through the heart rate variability in sleep cycle to make the sleep studies easier and also a person can record his dream time in the home. In this way we are able to use the biotelemetry in the recording of the dream time remotely. This method is much easier than the conventional method of Polysomnography.
Pak, Sangyeon,Lee, Juwon,Lee, Young-Woo,Jang, A-Rang,Ahn, Seongjoon,Ma, Kyung Yeol,Cho, Yuljae,Hong, John,Lee, Sanghyo,Jeong, Hu Young,Im, Hyunsik,Shin, Hyeon Suk,Morris, Stephen M.,Cha, SeungNam,Sohn American Chemical Society 2017 NANO LETTERS Vol.17 No.9
<P/><P>van der Waals heterostructures composed of two different monolayer crystals have recently attracted attention as a powerful and versatile platform for studying fundamental physics, as well as having great potential in future functional devices because of the diversity in the band alignments and the unique interlayer coupling that occurs at the heterojunction interface. However, despite these attractive features, a fundamental understanding of the underlying physics accounting for the effect of interlayer coupling on the interactions between electrons, photons, and phonons in the stacked heterobilayer is still lacking. Here, we demonstrate a detailed analysis of the strain-dependent excitonic behavior of an epitaxially grown MoS<SUB>2</SUB>/WS<SUB>2</SUB> vertical heterostructure under uniaxial tensile and compressive strain that enables the interlayer interactions to be modulated along with the electronic band structure. We find that the strain-modulated interlayer coupling directly affects the characteristic combined vibrational and excitonic properties of each monolayer in the heterobilayer. It is further revealed that the relative photoluminescence intensity ratio of WS<SUB>2</SUB> to MoS<SUB>2</SUB> in our heterobilayer increases monotonically with tensile strain and decreases with compressive strain. We attribute the strain-dependent emission behavior of the heterobilayer to the modulation of the band structure for each monolayer, which is dictated by the alterations in the band gap transitions. These findings present an important pathway toward designing heterostructures and flexible devices.</P>
Pak, Sangyeon,Jang, A-Rang,Lee, Juwon,Hong, John,Giraud, Paul,Lee, Sanghyo,Cho, Yuljae,An, Geon-Hyoung,Lee, Young-Woo,Shin, Hyeon Suk,Morris, Stephen M.,Cha, SeungNam,Sohn, Jung Inn,Kim, Jong Min The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.11
<P>Monolayered, semiconducting molybdenum disulfide (MoS2) is of considerable interest for its potential applications in next-generation flexible, wearable, and transparent photodetectors because it has outstanding physical properties coupled with unique atomically thin dimensions. However, there is still a lack of understanding in terms of the underlying mechanisms responsible for the photoresponse dynamics, which makes it difficult to identify the appropriate device design strategy for achieving a fast photoresponse time in MoS2 photodetectors. In this study, we investigate the importance of surface functionalization on controlling the charge carrier densities in a MoS2 monolayer and in turn the corresponding behavior of the photoresponse in relation to the position of the Fermi-level and the energy band structure. We find that the p-doping and n-doping, which is achieved through the surface functionalization of the MoS2 monolayer, leads to devices with different photoresponse behavior. Specifically, the MoS2 devices with surface functional groups contributing to p-doping exhibited a faster response time as well as higher sensitivity compared to that observed for the MoS2 devices with surface functional groups contributing to n-doping. We attribute this difference to the degree of bending in the energy bands at the metal-semiconductor junction as a result of shifting in the Fermi-level position, which influences the optoelectronic transport properties as well as the recombination dynamics leading to a low dark and thus high detectivity and fast decay time. Based upon these findings, we have also demonstrated the broad applicability of surface functionalization by fabricating a flexible MoS2 photodetector that shows an outstanding decay time of 0.7 s, which is the fastest response time observed in flexible MoS2 detectors ever reported.</P>
Red green blue emissive lead sulfide quantum dots: heterogeneous synthesis and applications
Hou, Bo,Cho, Yuljae,Kim, Byung-Sung,Ahn, Docheon,Lee, Sanghyo,Park, Jong Bae,Lee, Young-Woo,Hong, John,Im, Hyunsik,Morris, Stephen M.,Sohn, Jung Inn,Cha, SeungNam,Kim, Jong Min Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.15
<P>Visible emission colloidal quantum dots (QDs) have shown promise in optical and optoelectronic applications. These QDs are typically composed of relatively expensive elements in the form of indium, cadmium, and gallium since alternative candidate materials exhibiting similar properties are yet to be realized. Herein, for the first time, we report red green blue (RGB) photoluminescences with quantum yields of 18% from earth-abundant lead sulfide (PbS) QDs. The visible emissive property is mainly attributed to a high degree of crystallinity even for the extremely small QD sizes (1-3 nm), which is realized by employing a heterogeneous reaction methodology at high growth temperatures (>170 °C). We demonstrate that the proposed heterogeneous synthetic method can be extended to the synthesis of other metal chalcogenide QDs, such as zinc sulfide and zinc selenide, which are promising for future industrial applications. More importantly, benefiting from the enlarged band gaps, the as-prepared PbS solar cells show an impressive open circuit voltage (∼0.8 V) beyond that reported to date.</P>
Hong, John,Kim, Byung-Sung,Yang, Seungmo,Jang, A-Rang,Lee, Young-Woo,Pak, Sangyeon,Lee, Sanghyo,Cho, Yuljae,Kang, Dongwoo,Shin, Hyeon Suk,Hong, Jin Pyo,Morris, Stephen M.,Cha, SeungNam,Sohn, Jung Inn Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.6
<P>Traditional synthetic routes for transition metal sulfides typically involve solution and thermal-based processes to exploit their favorable pseudo-capacitive properties. However, there is a practical need to develop alternative processes to fabricate metal sulfide electrodes because of the time-consuming processes (>12 h), additional heat-treatment to active reactants, relatively high post-heat-treatment temperature (200-400 °C) and non-scalable nature of existing synthetic routes. Herein, utilizing a solution-based sulfur precursor, one-dimensional single-crystalline Cu2S nanostructures have been successfully prepared <I>via</I> a solution-based direct synthesis process within 10 min at room temperature without the need for thermal treatment steps. The fabricated electrode exhibits a capacitance of 750 mF cm<SUP>−2</SUP> at a current density of 2 mA cm<SUP>−2</SUP>. Moreover, the rate capacitance is maintained at about 82.3% as the current density is increased to 40 mA cm<SUP>−2</SUP>, and the capacity retains 90.5% of the initial value after 20 000 cycles. Importantly, as this method involves a solution-based formulation it is compatible with roll-to-roll processes, which is promising for mass and scalable production of the electrodes. The synthetic method ensures a facile and efficient approach to fabricating scalable one-dimensional single crystalline Cu2S nanostructures, highlighting the uniqueness of the solution-based sulfur activation method.</P>
Pak, Sangyeon,Cho, Yuljae,Hong, John,Lee, Juwon,Lee, Sanghyo,Hou, Bo,An, Geon-Hyoung,Lee, Young-Woo,Jang, Jae Eun,Im, Hyunsik,Morris, Stephen M.,Sohn, Jung Inn,Cha, SeungNam,Kim, Jong Min American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.44
<P>Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS<SUB>2</SUB>/PbS QDs phototransistor with consecutive type II junctions. The effects of the built-in potential across the depletion region near the type II junction interface in the QD layers are found to improve the photoresponse as well as decrease the response times to 950 μs, which is the faster response time (by orders of magnitude) than that recorded for previously reported 2D/QD phototransistors. Also, by implementing an electric-field modulation of the MoS<SUB>2</SUB> channel, our experimental results reveal that the detectivity can be as large as 1 × 10<SUP>11</SUP> jones. This work demonstrates an important pathway toward designing hybrid phototransistors and mixed-dimensional van der Waals heterostructures.</P> [FIG OMISSION]</BR>