119 research outputs found
Surface morphology engineering of metal oxide-transition metal dichalcogenide heterojunction
No full textA tremendous effort has been made to develop 2D materials-based FETs for electronic applications due to their atomically thin structures. Typically, the electrical performance of the device can vary with the surface roughness and thickness of the channel layer. Therefore, a two-step surface engineering process is demonstrated to tailor the surface roughness and thickness of MoSe2 multilayers involving exposure of O2 plasma followed by dipping in (NH4)2S(aq) solution. The O2 plasma treatment generated an amorphous MoOx layer to form a MoOx/MoSe2 heterojunction, and the (NH4)2S(aq) treatment tailored the surface roughness of the heterojunction. The ON/OFF current ratio of MoSe2 FET is about 1.1 × 105 and 5.7 × 104 for bare and chemically etched MoSe2, respectively. The surface roughness of the chemically treated MoSe2 is higher than that of the bare, 4.2 ± 0.5 nm against 3.6 ± 0.5 nm. Conversely, a 1-hour exposure of the multilayer MoOx/MoSe2 heterostructure with the (NH4)2S(aq) solution removed the amorphous oxide layer and scaled down the thickness of MoSe2 from ~92.2 nm to ~38.9 nm. The preliminary study shows that this simple two-step strategy can obtain a higher surface-area-to-volume ratio and thickness engineering with acceptable variation in electrical properties
Biomolecule based fiber supercapacitor for implantable device
No full textWith the growing demand for electronic medical devices for healthcare applications, we studied an implantable supercapacitor that can operate in an implantable electronic device. Here, we report a flexible implantable fiber supercapacitor for an in vivo energy storage device. The fiber supercapacitor has a high flexibility and a high potential to be applied in an implant device because the fiber can be implanted in the blood vessel and the wound can be stitched with the fiber-like suture. The fiber electrodes were fabricated in a biscrolling process that trapped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ferritin nanoclusters within multiwalled carbon nanotube (MWNT) sheets that provide mechanical strength and electrical conductivity. In addition, the supercapacitor is biocompatible because the MWNT sheets are coated with biocompatible materials such as PEDOT:PSS and ferritin. The areal capacitance of the PEDOT:PSS/ferritin/MWNT fiber supercapacitor was 32.9 mF/cm2 in a phosphate buffered saline solution, and the areal energy density was 0.82 μWh/cm2; these values are 52 times higher than that of the guest-free MWNT yarn. The supercapacitor operated well in a mouse and exhibited excellent biocompatibility; the capacitance was maintained above 90% in the mouse after eight days. © 2018 Elsevier Ltd1
Harvesting electrical energy from torsional thermal actuation driven by natural convection
No full textThe development of practical, cost-effective systems for the conversion of low-grade waste heat to electrical energy is an important area of renewable energy research. We here demonstrate a thermal energy harvester that is driven by the small temperature fluctuations provided by natural convection. This harvester uses coiled yarn artificial muscles, comprising well-aligned shape memory polyurethane (SMPU) microfibers, to convert thermal energy to torsional mechanical energy, which is then electromagnetically converted to electrical energy. Temperature fluctuations in a yarn muscle, having a maximum hot-to-cold temperature difference of about 13 degrees C, were used to spin a magnetic rotor to a peak torsional rotation speed of 3,000 rpm. The electromagnetic energy generator converted the torsional energy to electrical energy, thereby producing an oscillating output voltage of up to 0.81 V and peak power of 4 W/kg, based on SMPU mass.This work was supported by the Creative Research Initiative Center for Self-Powered Actuation of the National Research Foundation and the Ministry of Science, ICT & Future Planning (MSIP) in Korea. Support in Australia was from Centre of Excellence funding from the Australian Research Council. Support in the USA was from Air Force Grant AOARD-FA2386-13-4119, Air Force Office of Scientific Research grant FA9550-15-1-0089, and Robert A. Welch Foundation grant AT-0029
Elastomeric and Dynamic MnO2/CNT Core-Shell Structure Coiled Yarn Supercapacitor
No full textReversibly deformable and highly performing solid-state yarn supercapacitors are obtained using MnO2-deposited microcoiled yarn electrodes. The core(CNT)–shell(MnO2)-structured coiled electrodes achieve high stretchability (37.5%) without the help of elastomeric substrates, minimizing the size of the supercapacitors. Therefore, high specific capacitances of 34.6 F cm−3, 61.25 mF cm−2, and 2.72 mF cm−1 are achieved for coiled supercapacitors without impairing mechanical stretchability or electrochemical cyclability.This work was supported by the Creative Research Initiative Center for Self-powered Actuation and the Korea-US Air Force Cooperation Program Grant No. 2013K1A3A1A32035592 in Korea. Support at the University of Texas at Dallas was provided by Air Force Office of Scientific Research grants FA9550-15-1-0089, FA9550-14-1-0227, and FA2386-13-1-4119, NASA grants NNX14CS09P and NNX15CS05C, NSF grant CMMI 1120382, and the Robert A. Welch Foundation grant AT-0029. Additional support was from the Australian Research Council Discovery Grant DP110101073 and the Australian National Fabrication Facility
Microbuckled Mechano-electrochemical Harvesting Fiber for Self-Powered Organ Motion Sensors
No full textMechanical harvesters have attracted tremendous attention
as self-powered
strain sensors; previous harvesters required high stress to stretch
the fiber because of their high Young’s modulus and low elasticity.
We report on a mechano-electrochemical harvesting (MECH) fiber based
on the new buckle structure, which has a low Young’s modulus
(2 MPa) with high elasticity (up to 100%) in a similar physiological
fluid. MECH converts mechanical energy into electrical energy by changing
the capacitance due to changing the surface area caused by the microbuckle
on the surface. The damage to the cells can be minimized by their
softness; the fiber was stitched on the tissue of the pig stomach
while maintaining the performance like a suture fiber. Additionally,
the fiber successfully operated in an organ-similar system, which
is composed of the stomach or bladder of a pig. The fiber has a high
potential to be applied in wearable energy sources and self-powered
strain sensors
Complement activation and protein adsorption by carbon nanotubes
No full textAs a first step to validate the use of carbon nanotubes as novel vaccine or drug delivery devices, their interaction with a part of the human immune system, complement, has been explored. Haemolytic assays were conducted to investigate the activation of the human serum complement system via the classical and alternative pathways. Western blot and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques were used to elucidate the mechanism of activation of complement via the classical pathway, and to analyse the interaction of complement and other plasma proteins with carbon nanotubes. We report for the first time that carbon nanotubes activate human complement via both classical and alternative pathways. We conclude that complement activation by nanotubes is consistent with reported adjuvant effects, and might also in various circumstances promote damaging effects of excessive complement activation, such as inflammation and granuloma formation. C1q binds directly to carbon nanotubes. Protein binding to carbon nanotubes is highly selective, since out of the many different proteins in plasma, very few bind to the carbon nanotubes. Fibrinogen and apolipoproteins (AI, AIV and CIII) were the proteins that bound to carbon nanotubes in greatest quantit
Unsupervised emotion detection for Twitter with sarcasm detection
No full textSocial media has become a common avenue for transmission of information. There has been a rising trend in research on sentimental analysis and opinion mining on Twitter in the recent years due to the popularity of Twitter. The aim of these research is to develop ways to extract sentiments or opinions of the public, which are beneficial in applications such as business and government intelligence.
Many methodologies and approaches used for sentiment analysis and opinion mining on Twitter often faced difficulties in classifying tweets that are sarcastic in nature. Sarcasm is a special communication method that uses words that means opposite to what the author is trying to convey. The words used in a sentence may be positive in nature but the underlying emotion that was conveyed was a negative one.
In the report, I propose a sentimental analysis model to incorporate a sarcasm detector into an existing sentiment analysis method to enhance the performance of the sentiment classification of a tweet.
The sarcasm detector is based on explicit sarcastic labels found in the hashtags of the tweets. These sarcastic tweets are identified and removed from the test data. A self-generated lexicon approach was used to create a polarity dictionary which was then used to calculate and classify the remaining test data based on the polarity of tweets.
The results show that the proposed method performed better than the original method when identifying both positive and negative.Bachelor of Engineering (Computer Engineering
Biomolecule based fiber supercapacitor for implantable device
No full textWith the growing demand for electronic medical devices for healthcare applications, we studied an implantable supercapacitor that can operate in an implantable electronic device. Here, we report a flexible implantable fiber supercapacitor for an in vivo energy storage device. The fiber supercapacitor has a high flexibility and a high potential to be applied in an implant device because the fiber can be implanted in the blood vessel and the wound can be stitched with the fiber-like suture. The fiber electrodes were fabricated in a biscrolling process that trapped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ferritin nanoclusters within multiwalled carbon nanotube (MWNT) sheets that provide mechanical strength and electrical conductivity. In addition, the supercapacitor is biocompatible because the MWNT sheets are coated with biocompatible materials such as PEDOT: PSS and ferritin. The areal capacitance of the PEDOT:PSS/ferritin/MWNT fiber supercapacitor was 32.9 mF/cm(2) in a phosphate buffered saline solution, and the areal energy density was 0.82 mu Wh/cm(2); these values are 52 times higher than that of the guest-free MWNT yarn. The supercapacitor operated well in a mouse and exhibited excellent biocompatibility; the capacitance was maintained above 90% in the mouse after eight days.This work was supported by the Creative Research Initiative Center for Self-Powered Actuation and the DGIST R&D Program (18-NT-02) of the Ministry of Science, ICT and Future Planning in Korea. Support at the University of Texas at Dallas was provided by the Air Force Office of Scientific Research grants FA9550-15-1-0089 and FA2386-13-1-4119, NASA grant NNX15CSS05C, and Robert A. Welch Foundation grant AT-0029
Integrated Mechano-Electrochemical Harvesting Fiber and Thermally Responsive Artificial Muscle for Self-Powered Temperature–Strain Dual-Parameter Sensor
No full textSignificant progress in healthcare fields around the world has inspired us to develop a wearable strain–temperature sensor that can monitor biomedical signals in daily life. This novel self-powered temperature–strain dual-parameter sensor comprises a mechano-electrochemical harvester (MEH) and a thermally responsive artificial muscle (TAM). The MEHTAM system generates electricity from strain and thermal fluctuations. In addition, the sensor is comfortable to wear, owing to its stretchability (>100%), softness (<3 MPa), and one-dimensional fibers (diameter 230 μm). The MEH induces a change in the electrochemical capacitance, resulting in an electrical signal under applied strain (34 μA/m) and stress (20 μA/(m·MPa)). The TAM can be used as a mechanical temperature sensor, because the tensile stroke responds linearly to changes in temperature. As the harvester and artificial muscle are combined, the MEHTAM system generates electricity, owing to external and internal mechanical stimuli caused by muscle contractions as a response to temperature changes. The MEHTAM system that we have developed—a self-powered, strain–temperature dual-parameter sensor that is soft, stretchable, and fiber-shaped—is an interesting candidate for the production of comfortable, wearable, dual-parameter sensors
- …
