| 1. |
- Xie, Sisi, et al.
(författare)
-
Dietary ketone body-escalated histone acetylation in megakaryocytes alleviates chemotherapy-induced thrombocytopenia
- 2022
-
Ingår i: Science Translational Medicine. - : AMER ASSOC ADVANCEMENT SCIENCE. - 1946-6234 .- 1946-6242. ; 14:673
-
Tidskriftsartikel (refereegranskat)abstract
- Chemotherapy-induced thrombocytopenia (CIT) is a severe complication in patients with cancer that can lead to impaired therapeutic outcome and survival. Clinically, therapeutic options for CIT are limited by severe adverse effects and high economic burdens. Here, we demonstrate that ketogenic diets alleviate CIT in both animals and humans without causing thrombocytosis. Mechanistically, ketogenic diet-induced circulating beta-hydroxybutyrate (beta-OHB) increased histone H3 acetylation in bone marrow megakaryocytes. Gain- and loss-of-function experiments revealed a distinct role of 3-beta-hydroxybutyrate dehydrogenase (BDH)-mediated ketone body metabolism in promoting histone acetylation, which promoted the transcription of platelet biogenesis genes and induced thrombocytopoiesis. Genetic depletion of the megakaryocyte-specific ketone body transporter monocarboxylate transporter 1 (MCT1) or pharmacological targeting of MCT1 blocked beta-OHB-induced thrombocytopoiesis in mice. A ketogenesis-promoting diet alleviated CIT in mouse models. Moreover, a ketogenic diet modestly increased platelet counts without causing thrombocytosis in healthy volunteers, and a ketogenic lifestyle inversely correlated with CIT in patients with cancer. Together, we provide mechanistic insights into a ketone body-MCT1-BDH-histone acetylation-platelet biogenesis axis in megakaryocytes and propose a non-toxic, low-cost dietary intervention for combating CIT.
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| 2. |
- Arjmandi-Tash, Hadi, et al.
(författare)
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Zero-Depth Interfacial Nanopore Capillaries
- 2018
-
Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 30:9
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Tidskriftsartikel (refereegranskat)abstract
- High-fidelity analysis of translocating biomolecules through nanopores demands shortening the nanocapillary length to a minimal value. Existing nanopores and capillaries, however, inherit a finite length from the parent membranes. Here, nanocapillaries of zero depth are formed by dissolving two superimposed and crossing metallic nanorods, molded in polymeric slabs. In an electrolyte, the interface shared by the crossing fluidic channels is mathematically of zero thickness and defines the narrowest constriction in the stream of ions through the nanopore device. This novel architecture provides the possibility to design nanopore fluidic channels, particularly with a robust 3D architecture maintaining the ultimate zero thickness geometry independently of the thickness of the fluidic channels. With orders of magnitude reduced biomolecule translocation speed, and lowered electronic and ionic noise compared to nanopores in 2D materials, the findings establish interfacial nanopores as a scalable platform for realizing nanofluidic systems, capable of single-molecule detection.
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| 3. |
- Chen, Libo, et al.
(författare)
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Artificial tactile peripheral nervous system supported by self-power transducers
- 2021
-
Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 82
-
Tidskriftsartikel (refereegranskat)abstract
- The tactile peripheral nervous system innervating human hands, which is essential for sensitive haptic exploration and dexterous object manipulation, features overlapped receptive fields in the skin, arborization of peripheral neurons and many-to-many synaptic connections. Inspired by the structural features of the natural system, we report a supersensitive artificial slowly adapting tactile afferent nervous system based on the triboelectric nanogenerator technology. Using tribotronic transistors in the design of mechanoreceptors, the artificial afferent nervous system exhibits the typical adapting behaviours of the biological counterpart in response to mechanical stimulations. The artificial afferent nervous system is self-powered in the transduction and event-driven in the operation. Moreover, it has inherent proficiency of neuromorphic signal processing, delivering a minimum resolvable dimension two times smaller than the inter-receptor distance which is the lower limit of the dimension that existing electronic skins can resolve. These results open up a route to scalable neuromorphic skins aiming at the level of human?s exceptional perception for neurorobotic and neuroprosthetic applications.
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| 4. |
- Chen, Libo, et al.
(författare)
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Spike timing–based coding in neuromimetic tactile system enables dynamic object classification
- 2024
-
Ingår i: Science. - 0036-8075. ; 384, s. 660-665
-
Tidskriftsartikel (refereegranskat)abstract
- Rapid processing of tactile information is essential to human haptic exploration and dexterous object manipulation. Conventional electronic skins generate frames of tactile signals upon interaction with objects. Unfortunately, they are generally ill-suited for efficient coding of temporal information and rapid feature extraction. In this work, we report a neuromorphic tactile system that uses spike timing, especially the first-spike timing, to code dynamic tactile information about touch and grasp. This strategy enables the system to seamlessly code highly dynamic information with millisecond temporal resolution on par with the biological nervous system, yielding dynamic extraction of tactile features. Upon interaction with objects, the system rapidly classifies them in the initial phase of touch and grasp, thus paving the way to fast tactile feedback desired for neuro-robotics and neuro-prosthetics.
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| 5. |
- Dematties, Dario, et al.
(författare)
-
A Generalized Transformer-Based Pulse Detection Algorithm
- 2022
-
Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 7:9, s. 2710-2720
-
Tidskriftsartikel (refereegranskat)abstract
- Pulse-like signals are ubiquitous in the field of single molecule analysis, e.g., electrical or optical pulses caused by analyte translocations in nanopores. The primary challenge in processing pulse-like signals is to capture the pulses in noisy backgrounds, but current methods are subjectively based on a user-defined threshold for pulse recognition. Here, we propose a generalized machine-learning based method, named pulse detection transformer (PETR), for pulse detection. PETR determines the start and end time points of individual pulses, thereby singling out pulse segments in a time-sequential trace. It is objective without needing to specify any threshold. It provides a generalized interface for downstream algorithms for specific application scenarios. PETR is validated using both simulated and experimental nanopore translocation data. It returns a competitive performance in detecting pulses through assessing them with several standard metrics. Finally, the generalization nature of the PETR output is demonstrated using two representative algorithms for feature extraction.
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| 6. |
- Dematties, Dario, et al.
(författare)
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Deep Learning of Nanopore Sensing Signals Using a Bi-Path Network
- 2021
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:9, s. 14419-14429
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Tidskriftsartikel (refereegranskat)abstract
- Temporal changes in electrical resistance of a nanopore sensor caused by translocating target analytes are recorded as a sequence of pulses on current traces. Prevalent algorithms for feature extraction in pulse-like signals lack objectivity because empirical amplitude thresholds are user-defined to single out the pulses from the noisy background. Here, we use deep learning for feature extraction based on a bipath network (B-Net). After training, the B-Net acquires the prototypical pulses and the ability of both pulse recognition and feature extraction without a priori assigned parameters. The B-Net is evaluated on simulated data sets and further applied to experimental data of DNA and protein translocation. The B-Net results are characterized by small relative errors and stable trends. The B-Net is further shown capable of processing data with a signal-to-noise ratio equal to 1, an impossibility for threshold-based algorithms. The B-Net presents a generic architecture applicable to pulse-like signals beyond nanopore currents.
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| 7. |
- Han, Yuanyuan, et al.
(författare)
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Flexible conductive silk-PPy hydrogel toward wearable electronic strain sensors
- 2022
-
Ingår i: Biomedical Materials. - : IOP Publishing Ltd. - 1748-6041 .- 1748-605X. ; 17:2
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Tidskriftsartikel (refereegranskat)abstract
- Conductive hydrogels have been studied as promising materials for the flexible and wearable bioelectronics, because of their unique electrical and mechanical properties. Addition of conducting polymers in biomaterial-based hydrogel matrix is a simple yet effective way to construct hydrogels with good conductivity and flexibility. In this work, a conductive hydrogel composed by a silk hydrogel and a conducting polymer, polypyrrole (PPy), is developed via in situ polymerization of pyrrole into the silk fibroin network. The silk-PPy hydrogel shows high conductivity (26 S m(-1)), as well as sensitive and fast responses to corresponding conformation changes. Taking advantages of these properties, flexible and wearable strain sensors are proposed for the monitoring of various body movements, which can detect both the large and subtle human motions with good sensitivity, reproducibility and stability. The hybridization of biomaterials and conducting polymers endows the multifunctions of the conductive hydrogels, thus showing considerable potentials in the advancement of the wearable electronics.
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| 8. |
- Li, Chen, et al.
(författare)
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Rapid Four-Point Sweeping Method to Investigate Hysteresis of MoS2 FET
- 2020
-
Ingår i: IEEE Electron Device Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0741-3106 .- 1558-0563. ; 41:9, s. 1356-1359
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Tidskriftsartikel (refereegranskat)abstract
- Hysteresis is a frequently observed phenomenon in the transfer characteristics of thin film transistors. Charge trapping/de-trapping processes of gate oxide and gate-channel interface are commonly known to be the origin of hysteresis and correlated to low frequency noise (LFN) properties of the devices. In this letter, a rapid four-point sweeping method (RFSM) is proposed to reveal the dependence of hysteresis, as well as the distribution of effective trap density on sweeping rate and gate bias range. Based on the RFSM, the hysteresis properties of four-layer MoS2 FETs are studied in detail. The experimental results demonstrate that the hysteresis and trap density at different frequencies and gate voltages, which could further roughly map the traps with different time constants and energy depths, can be obtained by the simple RFSM. Trap density estimated by RFSM shows a comparable range with that extracted from LFN, indicating that the traps inducing the hysteresis may also cause LFN.
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| 9. |
- Li, Hui, et al.
(författare)
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Accelerating Gas Adsorption on 3D Percolating Carbon Nanotubes
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- In the field of electronic gas sensing, low-dimensional semiconductors such as single-walled carbon nanotubes (SWCNTs) can offer high detection sensitivity owing to their unprecedentedly large surface-to-volume ratio. The sensitivity and responsivity can further improve by increasing their areal density. Here, an accelerated gas adsorption is demonstrated by exploiting volumetric effects via dispersion of SWCNTs into a percolating three-dimensional (3D) network in a semiconducting polymer. The resultant semiconducting composite film is evaluated as a sensing membrane in field effect transistor (FET) sensors. In order to attain reproducible characteristics of the FET sensors, a pulsed-gate-bias measurement technique is adopted to eliminate current hysteresis and drift of sensing baseline. The rate of gas adsorption follows the Langmuir-type isotherm as a function of gas concentration and scales with film thickness. This rate is up to 5 times higher in the composite than only with an SWCNT network in the transistor channel, which in turn results in a 7-fold shorter time constant of adsorption with the composite. The description of gas adsorption developed in the present work is generic for all semiconductors and the demonstrated composite with 3D percolating SWCNTs dispersed in functional polymer represents a promising new type of material for advanced gas sensors.
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| 10. |
- Li, Shiyu, et al.
(författare)
-
Docking and Activity of DNA Polymerase on Solid-State Nanopores
- 2022
-
Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 7:5, s. 1476-1483
-
Tidskriftsartikel (refereegranskat)abstract
- Integration of motor enzymes with biological nanopores has enabled commercial DNA sequencing technology; yet studies of the similar principle applying to solid-state nanopores are limited. Here, we demonstrate the real-life monitoring of phi29 DNA polymerase (DNAP) docking onto truncated-pyramidal nanopore (TPP) arrays through both electrical and optical readout. To achieve effective docking, atomic layer deposition of hafnium oxide is employed to reduce the narrowest pore opening size of original silicon (Si) TPPs to sub-10 nm. On a single TPP with pore opening size comparable to DNAP, ionic current measurements show that a polymerase-DNA complex can temporally dock onto the TPP with a certain docking orientation, while the majority become translocation events. On 5-by-5 TPP arrays, a label-free optical detection method using Ca2+ sensitive dye, are employed to detect the docking dynamics of DNAP. The results show that this label-free detection strategy is capable of accessing the docking events of DNAP on TPP arrays. Finally, we examine the activity of docked DNAP by performing on-site rolling circle amplification to synthesize single-stranded DNA (ssDNA), which serves as a proof-of-concept demonstration of utilizing this docking scheme for emerging nanopore sensing applications.
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| 11. |
- Li, Shiyu, et al.
(författare)
-
Dynamics of DNA Clogging in Hafnium Oxide Nanopores
- 2020
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 124:51, s. 11573-11583
-
Tidskriftsartikel (refereegranskat)abstract
- Interfacing solid-state nanopores with biological systems has been exploited as a versatile analytical platform for analysis of individual biomolecules. Although clogging of solid-state nanopores due to nonspecific interactions between analytes and pore walls poses a persistent challenge in attaining the anticipated sensing efficacy, insufficient studies focus on elucidating the clogging dynamics. Herein, we investigate the DNA clogging behavior by passing double-stranded (ds) DNA molecules of different lengths through hafnium oxide(HfO2)-coated silicon (Si) nanopore arrays, at different bias voltages and electrolyte pH values. Employing stable and photoluminescent-free HfO2/Si nanopore arrays permits a parallelized visualization of DNA clogging with confocal fluorescence microscopy. We find that the probability of pore clogging increases with both DNA length and bias voltage. Two types of clogging are discerned: persistent and temporary. In the time-resolved analysis, temporary clogging events exhibit a shorter lifetime at higher bias voltage. Furthermore, we show that the surface charge density has a prominent effect on the clogging probability because of electrostatic attraction between the dsDNA and the HfO2 pore walls. An analytical model based on examining the energy landscape along the DNA translocation trajectory is developed to qualitatively evaluate the DNA–pore interaction. Both experimental and theoretical results indicate that the occurrence of clogging is strongly dependent on the configuration of translocating DNA molecules and the electrostatic interaction between DNA and charged pore surface. These findings provide a detailed account of the DNA clogging phenomenon and are of practical interest for DNA sensing based on solid-state nanopores.
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| 12. |
- Li, Shiyu, et al.
(författare)
-
Label-Free Optical Detection of DNA Polymerase Docking on Solid-State Nanopore Arrays
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Integration of motor enzymes with biological nanopores has enabled commercial DNA sequencing, yet studies of the similar principle applying to solid-state nanopores are limited. Here, we demonstrate the label-free optical detection of phi29 DNA polymerase (DNAP) docking onto truncated-pyramidal nanopores (TPP). Atomic layer deposition of hafnium oxide is employed to shrink the pore opening size of original silicon (Si) TPP to sub-10 nm. Ionic current measurements of single TPP of an opening size comparable to DNAP show that polymerase-DNA complexes can temporally dock onto the TPP with a certain docking orientation, while the majority are translocation events. A label-free optical detection method using Ca2+ sensitive dye is employed to detect the docking of DNAP on 5-by-5 nanopore arrays. The results of the proof-of-concept experiment show that this label-free detection strategy is capable of accessing the docking events of DNAP on solid-state nanopore arrays.
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| 13. |
- Pham, Ngan Hoang, et al.
(författare)
-
High thermoelectric power factor of p-type amorphous silicon thin films dispersed with ultrafine silicon nanocrystals
- 2020
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 127:24
-
Tidskriftsartikel (refereegranskat)abstract
- Silicon, a candidate as an abundant-element thermoelectric material for low-temperature thermal energy scavenging applications, generally suffers from rather low thermoelectric efficiency. One viable solution to enhancing the efficiency is to boost the power factor (PF) of amorphous silicon (a-Si) while keeping the thermal conductivity sufficiently low. In this work, we report that PF >1 m Wm−1 K−2 is achievable for boron-implanted p-type a-Si films dispersed with ultrafine crystals realized by annealing with temperatures ≤600 °C. Annealing at 550 °C initiates crystallization with sub-5-nm nanocrystals embedded in the a-Si matrix. The resultant thin films remain highly resistive and thus yield a low PF. Annealing at 600 °C approximately doubles the density of the sub-5-nm nanocrystals with a bimodal size distribution characteristic and accordingly reduces the fraction of the amorphous phase in the films. Consequently, a dramatically enhanced electrical conductivity up to 104 S/m and hence PF > 1 m Wm−1 K−2 measured at room temperature are achieved. The results show the great potential of silicon in large-scale thermoelectric applications and establish a route toward high-performance energy harvesting and cooling based on silicon thermoelectrics.
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| 14. |
- Pham, Ngan Hoang, et al.
(författare)
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Self-Limited Formation of Bowl-Shaped Nanopores for Directional DNA Translocation
- 2021
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:11, s. 17938-17946
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopores of on-demand dimensions and shapes can facilitate desired sensor functions. However, reproducible fabrication of arrayed nanopores of predefined dimensions remains challenging despite numerous techniques explored. Here, bowl-shaped nanopores combining properties of ultrathin membrane and tapering geometry are manufactured using a self-limiting process developed on the basis of standard silicon technology. The upper opening of the bowl-nanopores is 60–120 nm in diameter, and the bottom orifice reaches sub-5 nm. Current-voltage characteristics of the fabricated bowl-nanopores display insignificant rectification indicating weak ionic selectivity, in accordance to numerical simulations showing minor differences in electric field and ionic velocity upon the reversal of bias voltages. Simulations reveal, concomitantly, high-momentum electroosmotic flow downward along the concave nanopore sidewall. Collisions between the left and right tributaries over the bottom orifice drive the electroosmotic flow both up into the nanopore and down out of the nanopore through the orifice. The resultant asymmetry in electrophoretic–electroosmotic force is considered the cause responsible for the experimentally observed strong directionality in λ-DNA translocation with larger amplitude, longer duration, and higher frequencies for the downward movements from the upper opening than the upward ones from the orifice. Thus, the resourceful silicon nanofabrication technology is shown to enable nanopore designs toward enriching sensor applications.
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| 15. |
- Pi, Zhaoyang, et al.
(författare)
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Flexible piezoelectric nanogenerator made of poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) thin film
- 2014
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Ingår i: NANO ENERGY. - : Elsevier BV. - 2211-2855. ; 7, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a flexible nanogenerator based on direct piezoelectric effect using a spin-coated poly(vinytidenefluoride-co-trifluoroethylene) (PVDF-TrFE) thin film as functional layer has been fabricated on polyimide substrate. The as-prepared nanogenerator exhibits the open-circuit voltage up to 7 V and short-circuit current of 58 nA with current density of 0.56 mu A/Cm-2. The impact of the variation of strain rate on the electrical outputs of the nanogenerator has been characterized experimentally and analyzed theoretically. An analytical model that explains well the experimental results has been established. (C) 2014 Elsevier Ltd. All rights reserved.
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| 16. |
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| 17. |
- Tian, Lei, et al.
(författare)
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Understanding the Role of Surface States on Mesoporous NiO Films
- 2020
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:43
-
Tidskriftsartikel (refereegranskat)abstract
- Surface states of mesoporous NiO semiconductor films have particular properties differing from the bulk and are able to dramatically influence the interfacial electron transfer and adsorption of chemical species. To achieve a better performance of NiO-based p-type dye-sensitized solar cells (p-DSCs), the function of the surface states has to be understood. In this paper, we applied a modified atomic layer deposition procedure that is able to passivate 72% of the surface states on NiO by depositing a monolayer of Al2O3. This provides us with representative control samples to study the functions of the surface states on NiO films. A main conclusion is that surface states, rather than the bulk, are mainly responsible for the conductivity in mesoporous NiO films. Furthermore, surface states significantly affect dye regeneration (with I–/I3– as redox couple) and hole transport in NiO-based p-DSCs. A new dye regeneration mechanism is proposed in which electrons are transferred from reduced dye molecules to intra-bandgap states, and then to I3– species. The intra-bandgap states here act as catalysts to assist I3– reduction. A more complete mechanism is suggested to understand the particular hole transport behavior in p-DSCs, in which the hole transport time is independent of light intensity. This is ascribed to the percolation hole hopping on the surface states. When the concentration of surface states was significantly reduced, the light-independent charge transport behavior in pristine NiO-based p-DSCs transformed into having an exponential dependence on light intensity, similar to that observed in TiO2-based n-type DSCs. These conclusions on the function of surface states provide new insight into the electronic properties of mesoporous NiO films.
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| 18. |
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| 19. |
- Tseng, Chiao-Wei, et al.
(författare)
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Synergy of Ionic and Dipolar Effects by Molecular Design for pH Sensing beyond the Nernstian Limit
- 2020
-
Ingår i: Advanced Science. - : Wiley. - 2198-3844. ; 7:2
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge of interfacial interactions between analytes and functionalized sensor surfaces, from where the signal originates, is key to the development and application of electronic sensors. The present work explores the tunability of pH sensitivity by the synergy of surface charge and molecular dipole moment induced by interfacial proton interactions. This synergy is demonstrated on a silicon‐nanoribbon field‐effect transistor (SiNR‐FET) by functionalizing the sensor surface with properly designed chromophore molecules. The chromophore molecules can interact with protons and lead to appreciable changes in interface dipole moment as well as in surface charge state. In addition, the dipole moment can be tuned not only by the substituent on the chromophore but also by the anion in the electrolyte interacting with the protonated chromophore. By designing surface molecules to enhance the surface dipole moment upon protonation, an above‐Nernstian pH sensitivity is achieved on the SiNR‐FET sensor. This finding may bring an innovative strategy for tailoring the sensitivity of the SiNR‐FET‐based pH sensor toward a wide range of applications.
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| 20. |
- Wen, Chenyu, et al.
(författare)
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A Guide to Signal Processing Algorithms for Nanopore Sensors
- 2021
-
Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 6:10, s. 3536-3555
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Forskningsöversikt (refereegranskat)abstract
- Nanopore technology holds great promise for a wide range of applications such as biomedical sensing, chemical detection, desalination, and energy conversion. For sensing performed in electrolytes in particular, abundant information about the translocating analytes is hidden in the fluctuating monitoring ionic current contributed from interactions between the analytes and the nanopore. Such ionic currents are inevitably affected by noise; hence, signal processing is an inseparable component of sensing in order to identify the hidden features in the signals and to analyze them. This Guide starts from untangling the signal processing flow and categorizing the various algorithms developed to extracting the useful information. By sorting the algorithms under Machine Learning (ML)-based versus non-ML-based, their underlying architectures and properties are systematically evaluated. For each category, the development tactics and features of the algorithms with implementation examples are discussed by referring to their common signal processing flow graphically summarized in a chart and by highlighting their key issues tabulated for clear comparison. How to get started with building up an ML-based algorithm is subsequently presented. The specific properties of the ML-based algorithms are then discussed in terms of learning strategy, performance evaluation, experimental repeatability and reliability, data preparation, and data utilization strategy. This Guide is concluded by outlining strategies and considerations for prospect algorithms.
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| 21. |
- Wen, Chenyu, et al.
(författare)
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Assessing kinetics of surface adsorption-desorption of gas molecules via electrical measurements
- 2016
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 223, s. 791-798
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Tidskriftsartikel (refereegranskat)abstract
- Gas sensing represents a grand research and application field. Owing to their unique structure of single-atom/molecule thickness, the emerging two-dimensional (2D) semiconductors are anticipated to display ultrahigh sensitivity capable of detecting minute changes in surface charge. To support the vast variety of gas sensing applications for domestic gases and environmental control, rapid and reliable quantitative analysis of measurement results based on established sensing mechanism and kinetics is essential. The present work uses graphene-based 2D sensors as a model system to establish the analytical capability for assessing the adsorption-desorption kinetics of gas molecules via electrical characterization. By linking the electrical current in graphene to the surface coverage of gas molecules and by incorporating the non-steady-state initial conditions for adsorption and desorption, an analytical model is established. Important kinetic parameters including activation energy, equilibrium coverage and adsorption-desorption time constants are obtained. The model can also facilitate real-world applications in gas sensing.
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| 22. |
- Wen, Chenyu, et al.
(författare)
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Autogenic analyte translocation in nanopores
- 2019
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 60, s. 503-509
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Tidskriftsartikel (refereegranskat)abstract
- Nanopores have been widely studied for power generation and single-molecule detection. Although the power level generated by a single nanopore based on electrolyte concentration gradient is too low to be practically useful, such a power level is found sufficient to drive analyte translocation in nanopores. Here, we explore the simultaneous action of a solid-state nanopore as a nanopower generator and a nanoscale biosensor by exploiting the extremely small power generated to drive the analyte translocation in the same nanopore device. This autogenic analyte translocation is demonstrated using protein and DNA for their distinct shape, size and charge. The simple device structure allows for easy implementation of either electrical or optical readout. The obtained nanopore translocation is characterized by typical behaviors expected for an ordinary nanopore sensor powered by an external source. Extensive numerical simulation confirms the power generation and power level generated. It also reveals the fundamentals of autogenic translocation. As it requires no external power source, the sensing can be conducted with simple readout electronics and may allow for integration of high-density nanopores. Our approach demonstrated in this work may pave the way to practical high-throughput single-molecule nanopore sensing powered by the distributed energy harvested by the nanopores themselves.
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| 23. |
- Wen, Chenyu, et al.
(författare)
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Efficient reduction and exfoliation of graphite oxide by sequential chemical reduction and microwave irradiation
- 2014
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 194, s. 71-76
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Tidskriftsartikel (refereegranskat)abstract
- An efficient hybrid method combining chemical reduction and microwave irradiation is used to reduce graphite oxide. The hybrid reduction method achieved a carbon/oxygen ratio of 10.33 which is 2.7 times and 1.4 times higher than those obtained with chemical solution and solid-phase microwave irradiation only methods, respectively. The reduced graphene oxide obtained by the hybrid method had a conductance (1.19 × 104 S/m) 84.2 times higher than that by chemical solution and 15.6 times higher than that by solid-phase microwave irradiation. In addition, we reveal that microwave irradiation removes CO bonds more efficiently than CO bonds.
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| 24. |
- Wen, Chenyu, et al.
(författare)
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Fundamentals and potentials of solid-state nanopores : a review
- 2021
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Ingår i: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 54:2
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Forskningsöversikt (refereegranskat)abstract
- Solid-state nanopore (SSNP) technology presents an emerging single-molecule based analytical tool for separation and analysis of biomolecules or nanoparticles. Different prominent approaches have been pursued to attain the anticipated detection performance: process innovation to achieve pore size matching the physical dimensions of biomolecules so as to boost signal; electrolyte management to control translocation speed so as to improve signal quality; surface functionalisation to amplify molecular differences so as to enhance specificity; and implementation of additional, complementary means, such as optical, to manipulate the translocation so as to increase data fidelity. This review focuses on the fundamentals pertaining to the physical processes involved in nanopore sensing based on SSNPs of distinct shapes. It also provides a comprehensive picture regarding challenges and development trends in putting nanopore-based molecular sensors in use. This effort is facilitated by establishing physical-phenomenological models supported by experiment and numerical simulation. To assist the readership, the discussion starts from relatively simple cases and then develops towards complex systems, i.e. from open-pore state to analyte translocation and from single pores to pore arrays. Key physical parameter threading through these aspects is effective transport length that is simple to perceive and easy to calculate.
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| 25. |
- Wen, Chenyu, 1990-, et al.
(författare)
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Generalized Noise Study of Solid-State Nanopores at Low Frequencies
- 2017
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 2:2, s. 300-307
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Tidskriftsartikel (refereegranskat)abstract
- Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study lowfrequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nmthick SiNx membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.
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| 26. |
- Wen, Chenyu, et al.
(författare)
-
Group behavior of nanoparticles translocating multiple nanopores
- 2018
-
Ingår i: Analytical Chemistry. - Washington : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:22, s. 13483-13490
-
Tidskriftsartikel (refereegranskat)abstract
- Nanopores have been implemented as nanosensors for DNA sequencing, biomolecule inspection, chemical analysis, nanoparticle detection, etc. For high-throughput and parallelized measurement using nanopore arrays, individual addressability has been a crucial technological solution in order to enable scrutiny of signals generated at each and every nanopore. Here, an alternative pathway of employing arrayed nanopores to perform sensor functions is investigated by examining the group behavior of nanoparticles translocating multiple nanopores. As no individual addressability is required, fabrication of nanopore devices along with microfluidic cells and readout circuits can be greatly simplified. Experimentally, arrays of less than 10 pores are shown to be capable of analyzing translocating nanoparticles with a good signal-to-noise margin. According to theoretical predictions, more pores (than 10) per array can perform high-fidelity analysis if the noise level of the measurement system can be better controlled. More pores per array would also allow for faster measurement at lower concentration because of larger capture cross sections for target nanoparticles. By experimentally varying the number of pores, the concentration of nanoparticles, or the applied bias voltage across the nanopores, we have identified the basic characteristics of this multievent process. By characterizing average pore current and associated standard deviation during translocation and by performing physical modeling and extensive numerical simulations, we have shown the possibility of determining the size and concentration of two kinds of translocating nanoparticles over 4 orders of magnitude in concentration. Hence, we have demonstrated the potential and versatility of the multiple-nanopore approach for high-throughput nanoparticle detection.
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| 27. |
- Wen, Chenyu, et al.
(författare)
-
On current blockade upon analyte translocation in nanopores
- 2021
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 129:6
-
Tidskriftsartikel (refereegranskat)abstract
- Nanopore sensing primarily concerns quantifying the amplitude and shape of blockage current as well as the frequency of translocation events by analyzing the variation of the ionic current upon analyte translocation in a nanopore that represents an extremely simple device structure. To facilitate such an analysis, most reported physical-phenomenological models focus on geometrical factors. Here, we systematically analyze several other factors that may influence the amplitude and waveform of the blockage current. Our theoretical analysis starts with an analytical model based on geometry. It is then extended to include effects of surface conductance, electroosmotic flow, ionic concentration polarization, and induced charge on nanopore membranes. This approach allows for the examination of related electrokinetic and electrohydrodynamic aspects of analyte translocation in nanopores. The model results are confirmed using numerical simulation. The principal outcome of our theoretical scrutiny includes the identification of the respective determinatives of various factors as well as criteria for safely neglecting some of them when correlating the amplitude and waveform of blockage current to the properties of the translocating analyte. Our attempt to categorize these factors can be of practical implications in understanding the translocation process and for developing advanced data analysis algorithms as an effort to promote nanopore sensor applications.
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| 28. |
- Wen, Chenyu, et al.
(författare)
-
On nanopore DNA sequencing by signal and noise analysis of ionic current
- 2016
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 27
-
Tidskriftsartikel (refereegranskat)abstract
- DNA sequencing, i.e., the process of determining the succession of nucleotides on a DNA strand, has become a standard aid in biomedical research and is expected to revolutionize medicine. With the capability of handling single DNA molecules, nanopore technology holds high promises to become speedier in sequencing at lower cost than what are achievable with the commercially available optics-or semiconductor-based massively parallelized technologies. Despite tremendous progress made with biological and solid-state nanopores, high error rates and large uncertainties persist with the sequencing results. Here, we employ a nano-disk model to quantitatively analyze the sequencing process by examining the variations of ionic current when a DNA strand translocates a nanopore. Our focus is placed on signal-boosting and noise-suppressing strategies in order to attain the single-nucleotide resolution. Apart from decreasing pore diameter and thickness, it is crucial to also reduce the translocation speed and facilitate a stepwise translocation. Our best-case scenario analysis points to severe challenges with employing plain nanopore technology, i.e., without recourse to any signal amplification strategy, in achieving sequencing with the desired single-nucleotide resolution. A conceptual approach based on strand synthesis in the nanopore of the translocating DNA from single-stranded to double-stranded is shown to yield a 10-fold signal amplification. Although it involves no advanced physics and is very simple in mathematics, this simple model captures the essence of nanopore sequencing and is useful in guiding the design and operation of nanopore sequencing.
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| 29. |
- Wen, Chenyu, et al.
(författare)
-
On rectification of ionic current in nanopores
- 2019
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 91:22, s. 14597-14604
-
Tidskriftsartikel (refereegranskat)
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| 30. |
|
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| 31. |
- Wen, Chenyu, et al.
(författare)
-
Physical Model for Rapid and Accurate Determination of Nanopore Size via Conductance Measurement
- 2017
-
Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 2:10, s. 1523-1530
-
Tidskriftsartikel (refereegranskat)abstract
- Nanopores have been explored for various biochemical and nanoparticle analyses, primarily via characterizing the ionic current through the pores. At present, however, size determination for solid-state nanopores is experimentally tedious and theoretically unaccountable. Here, we establish a physical model by introducing an effective transport length, L (eff) that measures, for a symmetric nanopore, twice the distance from the center of the nanopore where the electric field is the highest to the point along the nanopore axis where the electric field falls to e-(1)of this maximum. By G = sigma(s0)/L-eff, a simple expression S-0=/(G, sigma, h, beta) is derived to algebraically correlate minimum nanopore cross-section area S (0)to nanopore conductance G, electrolyte conductivity a, and membrane thickness h with (3 to denote pore shape that is determined by the pore fabrication technique. The model agrees excellently with experimental results for nanopores in graphene, single-layer MoS2, and ultrathin SiNx films. The generality of the model is verified by applying it to micrometer-size pores.
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| 32. |
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| 33. |
- Wen, Chenyu
(författare)
-
Solid-State Nanopores for Sensing : From Theory to Applications
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanopore based sensing technology has been widely studied for a broad range of applications including DNA sequencing, protein profiling, metabolite molecules, and ions detection. The nanopore technology offers an unprecedented technological solution to meeting the demands of precision medicine on rapid, in-field, and low-cost biomolecule analysis. In general, nanopores are categorized in two families: solid-state nanopore (SSNP) and biological nanopore. The former is formed in a solid-state membrane made of SiNx, SiO2, silicon, graphene, MoS2, etc., while the latter represents natural protein ion-channels in cell membranes. Compared to biological pores, SSNPs are mechanically robust and their fabrication is compatible with traditional semiconductor processes, which may pave the way to their large-scale fabrication and high-density integration with standard control electronics. However, challenges remain for SSNPs, including poor stability, low repeatability, and relatively high background noise level. This thesis explores SSNPs from basic physical mechanisms to versatile applications, by entailing a balance between theory and experiment.The thesis starts with theoretical models of nanopores. First, resistance of the open pore state is studied based on the distribution of electric field. An important concept, effective transport length, is introduced to quantify the extent of the high field region. Based on this conductance model, the nanopores size of various geometrical shapes can be extracted from a simple resistance measurement. Second, the physical causality of ionic current rectification of geometrically asymmetrical nanopores is unveiled. Third, the origin of low-frequency noise is identified. The contribution of each noise component at different conditions is compared. Forth, a simple nano-disk model is used to describe the blockage of ionic current caused by DNA translocation. The signal and noise properties are analyzed at system level.Then, nanopore sensing experiments are implemented on cylinder SiNx nanopores and truncated-pyramid silicon nanopores (TPP). Prior to a systematic study, a low noise electrical characterization platform for nanopore devices is established. Signal acquisition guidelines and data processing flow are standardized. The effects of electroosmotic vortex in TPP on protein translocation dynamics are excavated. The autogenic translocation of DNA and proteins driven by the pW-level power generated by an electrolyte concentration gradient is demonstrated. Furthermore, by extending to a multiple pore system, the group translocation behavior of nanoparticles is studied. Various application scenarios, different analyte categories and divergent device structures accompanying with flexible configurations clearly point to the tremendous potential of SSNPs as a versatile sensor.
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| 34. |
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| 35. |
- Wen, Qin, et al.
(författare)
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Separating Direct Heat Flux Forcing and Freshwater Feedback on AMOC Change Under Global Warming
- 2023
-
Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 50:22
-
Tidskriftsartikel (refereegranskat)abstract
- The Atlantic meridional overturning circulation (AMOC) is predicted to weaken under global warming. Whether it is caused by heat flux or freshwater flux is under debate. Here we separate these two processes in changing the AMOC under global warming. The simulated AMOC is weakened during the first 600years and then gradually recovered to its initial state, with heat flux and freshwater feedback dominating at different timescales. Global warming immediately puts freshwater into the Southern Ocean, which triggers the initial AMOC weakening via altering surface temperature. Concurrently, the extensive heat into the ocean surface increases the temperature over the subpolar North Atlantic, reducing the deep convection and thus the AMOC in the subsequent 50–150years. Meanwhile, the Arctic sea ice melt leads to the AMOC shutdown. Subsequently, the salinity accumulation in the subtropical North Atlantic propagating northward to restart the North Atlantic deep convection is responsible for the AMOC recovery.
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| 36. |
- Xu, Xingxing, et al.
(författare)
-
Structural Changes of Mercaptohexanol Self-assembled Monolayers on Gold and their Influence on Impedimetric Aptamer Sensors
- 2019
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 91:22, s. 14697-14704
-
Tidskriftsartikel (refereegranskat)abstract
- Despite a large number of publications describing biosensors based on electrochemical impedance spectroscopy (EIS), little attention has been paid to the stability and reproducibility issues of the sensor interfaces. In this work, the stability and reproducibility of faradaic EIS analyses on the aptamer/mercaptohexanol (MCH) self-assembled monolayer (SAM) functionalized gold surfaces in ferri- and ferrocyanide solution were systematically evaluated prior to and after the aptamer-probe DNA hybridization. It is shown that the EIS data exhibited significant drift, and this significantly affected the reproducibility of the EIS signal of the hybridization. As a result, no significant difference between the charge transfer resistance (RCT) changes induced by the aptamer-target DNA hybridization and that caused by the drift could be identified. A conditioning of the electrode in the measurement solution for more than 12 hours was required to reach a stable RCT baseline prior to the aptamer-probe DNA hybridization. The monitored drift in RCT and CDL during the conditioning suggests that the MCH SAM on the gold surface reorganized to a thinner but more closely packed layer. We also observed that the hot binding buffer used in the following aptamer-probe DNA hybridization process could induce additional MCH and aptamer reorganization thus further drift in RCT. As a result, the RCT change caused by the aptamer-probe DNA hybridization was less than that caused by the hot binding buffer (blank control experiment). Therefore, it is suggested that the use of high temperature in the EIS measurement should be carefully evaluated or avoided. This work provides practical guidelines for the EIS measurements. Moreover, since SAM functionalized gold electrodes are widely used in biosensors, e.g., DNA sensors, an improved understanding of the origin of the observed drift is very important for the development of well-functioning and reproducible biosensors.
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| 37. |
- Yang, Hui, et al.
(författare)
-
Improving Electrical Performance of Few-Layer MoS2 FETs via Microwave Annealing
- 2019
-
Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 40:7, s. 1116-1119
-
Tidskriftsartikel (refereegranskat)abstract
- A few-layer molybdenum disulfide (MoS2) has attracted great attention because of its novel electrical and optoelectrical properties for devices. In this letter, we perform a systematic study on the evolution of the electrical performance of the few-layer MoS2 field-effect transistors (FETs) under microwave annealing. As a result, obvious improvements on electrical properties are achieved for the sample annealed in N-2 ambience between 420 and 840 W. The on/off current ratio of similar to 8.34 x 10(8) and the hysteresis of 2.1 V, which are similar to 150 times higher and similar to 2.1 times smaller compared with that of fabricated MoS2 FET, respectively. The proposed technique provides a new method to approach high-performance few-layer MoS2 FETs with minimized parasitic resistances.
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| 38. |
- Yao, Yao, et al.
(författare)
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On Induced Surface Charge in Solid-State Nanopores
- 2020
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Ingår i: Langmuir. - : AMER CHEMICAL SOC. - 0743-7463 .- 1520-5827. ; 36:30, s. 8874-8882
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopores constitute a versatile platform for study of ion transport in nanoconfinement. The electrical double layer (EDL) plays a vital role in such nanoconfinements, but effects of induced surface charge on the EDL in the presence of an external transmembrane electric field are yet to be characterized. Here, the formation of induced charge on the nanopore sidewall surface and its effects, via modulation of the EDL and electroosmotic flow, on the ionic current are elucidated using a novel experimental setup with solid-state truncated-pyramidal nanopores. This study consists of three complementary approaches, i.e., an analytical model for induced surface charge, numerical simulation of induced surface charge, electroosmotic flow, and ionic current, and experimental validation with respect to the ionic current. The induced surface charge is generated by polarization in the dielectric membrane as a response to the applied electric field. This charge generation results in a nonuniform density of surface charge along the nanopore sidewall. It further causes ions in the electrolyte to redistribute, leading to a massive accumulation of single-polarity ions in the EDL and their counterions near the smaller opening of the nanopore. It also alters electrohydrodynamic properties in the nanopore, giving rise to the formation of electroosmotic vortexes in the vicinity of the smaller opening of the nanopore. Finally, the pattern of the electroosmotic flow can significantly influence the transport properties of the nanopore.
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| 39. |
- Ye, Qiangqiang, et al.
(författare)
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Ultra-Sensitive and Responsive Capacitive Humidity Sensor Based on Graphene Oxide
- 2015
-
Ingår i: Proceedings of 2015 ieee 11th international conference on ASIC (ASICON). - : IEEE. - 9781479984855
-
Konferensbidrag (refereegranskat)abstract
- Humidity sensors have attracted extensive attentions due to their various applications in environment monitoring, health care and internet of things. Graphene oxide has recently been exploited as a humidity sensing material because of its good hydrophilicity and excellent sensitivity. Here we report an ultra-sensitive and responsive capacitive humidity sensor using graphene oxide as sensing material. A capacitance change of ten times is observed when the relative humidity changes from 50% to 90%. The response and recovery time of the sensor are measured to be 0.066 and 0.154 s, respectively, which are several orders of magnitude shorter than conventional humidity sensors. Furthermore, its responses to flow rate, temperature and other vapors are also characterized.
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| 40. |
- Zeng, Shuangshuang, et al.
(författare)
-
A Nanopore Array of Individual Addressability Enabled by Integrating Microfluidics and a Multiplexer
- 2020
-
Ingår i: IEEE Sensors Journal. - : IEEE. - 1530-437X .- 1558-1748. ; 20:3, s. 1558-1563
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopores (SSN) are of significant potential as a versatile tool for chemical sensing, biomolecule inspection, nanoparticle detection, etc. High throughput characterization of SSN in an arrayed format is highly desired for a wide range of applications. Herein, we demonstrate a novel design to integrate an SSN array with microfluidics and a multiplexer. Ionic current measurement on each nanopore can then be individually addressed fluidically and/or electrically with minimum cross talk (electric leakage). This integration provides a scalable platform for automated high-throughput, low-cost, and rapid electrical characterization potentially of a large number of SSN.
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| 41. |
- Zeng, Shuangshuang, et al.
(författare)
-
Controlled size reduction and its underlying mechanism to form solid-state nanopores via electron beam induced carbon deposition
- 2019
-
Ingår i: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 30:45
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopores have drawn considerable attention for their potential applications in DNA sequencing and nanoparticle analysis. However, fabrication of nanopores, especially those of diameter below 30 nm, requires sophisticated techniques. Here, a versatile method to controllably reduce the diameter of prefabricated large-size pores down to sub-30 nm without greatly increasing the effective pore depth from the original membrane thickness is shown. This method exploits carbon deposition achieved via hydrocarbon evaporation, induced by an incident beam of electrons, and subsequent dissociation of hydrocarbon to solid carbon deposits. The carbon deposition employs a conventional scanning electron microscope equipped with direct visual feedback, along with a stable hydrocarbon source nearby the sample. This work systematically studies how electron beam accelerating voltage, imaging magnification, initial pore size and membrane composition affect the process of pore size reduction. Secondary electrons generated in the membrane material are confirmed to be the main cause of the dissociation of hydrocarbon. Thicker carbon deposited on one side than on the other of the membrane results in an asymmetric nanopore shape and a rectifying ionic transport. A physico-phenomenological model combined with Monte Carlo simulations is proposed to account for the observed carbon deposition behaviors.
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| 42. |
- Zeng, Shuangshuang, et al.
(författare)
-
Mechanism and kinetics of lipid bilayer formation in solid-state nanopores
- 2020
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 36:6, s. 1446-1453
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopores provide a highly versatile platform for rapid electrical detection and analysis of single molecules. Lipid bilayer coating of the nanopores can reduce nonspecific analyte adsorption to the nanopore sidewalls and increase the sensing selectivity by providing possibilities for tethering specific ligands in a cell-membrane mimicking environment. However, the mechanism and kinetics of lipid bilayer formation from vesicles remain unclear in the presence of nanopores. In this work, we used a silicon-based, truncated pyramidal nanopore array as the support for lipid bilayer formation. Lipid bilayer formation in the nanopores was monitored in real time by the change in ionic current through the nanopores. Statistical analysis revealed that a lipid bilayer is formed from the instantaneous rupture of individual vesicle upon adsorption in the nanopores, differing from the generally agreed mechanism that lipid bilayer forms at a high vesicle surface coverage on a planar support. The dependence of the lipid bilayer formation process on the applied bias, vesicle size, and concentration was systematically studied. In addition, the nonfouling properties of the lipid bilayer coated nanopores were demonstrated during long single-stranded DNA translocation through the nanopore array. The findings indicate that the lipid bilayer formation process can be modulated by introducing nanocavities intentionally on the planar surface to create active sites or changing the vesicle size and concentration.
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| 43. |
- Zeng, Shuangshuang, et al.
(författare)
-
Rectification of protein translocation in truncated-pyramidal nanopores
- 2019
-
Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 14, s. 1056-1062
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopore technology presents an emerging single-molecule-based analytical tool for the separation and analysis of nanoparticles. Different approaches have been pursued to attain the anticipated detection performance. Here, we report the rectification behaviour of protein translocation through silicon-based truncated pyramidal nanopores. When the size of translocating proteins is comparable to the smallest physical constriction of the nanopore, the frequency of translocation events observed is lower for proteins that travel from the larger to the small opening of the nanopore than for those that travel in the reverse direction. When the proteins are appreciably smaller than the nanopore, an opposite rectification in the frequency of translocation events is evident. The maximum rectification factor achieved is around ten. Numerical simulations reveal the formation of an electro-osmotic vortex in such asymmetric nanopores. The vortex–protein interaction is found to play a decisive role in rectifying the translocation in terms of polarity and amplitude. The reported phenomenon can be potentially exploitable for the discrimination of various nanoparticles.
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| 44. |
- Zeng, Shuangshuang, et al.
(författare)
-
Single molecule detection via solid state carbon nanopore
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Single molecule detection is of vital importance for fundamental biotechnology research and practical applications. Among the numerous single molecule detection techniques, solid-state nanopores have been developed as single molecule sensors for the investigation of unlabeled biopolymers such as DNA, RNA and protein owing to their robustness, pore size controllability and tunability of physical/chemical properties. The most commonly used method today to form ultra-small nanopores relies on using focused high energy electron beams on a transmission electron microscope (TEM). However, the sophisticated operation of TEM, high cost and low throughput limit its extensive applications. In this work, we start with electron beam lithography combined with reactive ion etching to massively prefabricate nanopores with relatively large size in free-standing silicon nitride membranes. Then, electron beam irradiation is used to deposit carbon with a conventional scanning electron microscope so as to reduce the size of prefabricated pores. This process leads to the controllable formation of solid-state carbon nanopores sub-30 nm in diameter. We subsequently use the carbon nanopores to study translocation of λ-DNA as a demonstration of the capability of such carbon nanopores. By tuning bias voltage, the translocation events show regular changes in amplitude, dwell time and appearance frequency. With this advanced nanopore platform, detection of single DNA molecules is achieved with a high signal-to-noise ratio of ~6.
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| 45. |
- Zhao, Jie, et al.
(författare)
-
A Sequential Process of Graphene Exfoliation and Site-Selective Copper/Graphene Metallization Enabled by Multifunctional 1-Pyrenebutyric Acid Tetrabutylammonium Salt
- 2019
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:6, s. 6448-6455
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports a procedure leading to shear exfoliation of pristine few-layer graphene flakes in water and subsequent site-selective formation of Cu/graphene films on polymer substrates, both of which are enabled by employing the water soluble 1-pyrenebutyric acid tetrabutylammonium salt (PyB-TBA). The exfoliation with PyB-TBA as an enhancer leads to as-deposited graphene films dried at 90 °C that are characterized by electrical conductivity of ∼110 S/m. Owing to the good affinity of the tetrabutylammonium cations to the catalyst PdCl42–, electroless copper deposition selectively in the graphene films is initiated, resulting in a self-aligned formation of highly conductive Cu/graphene films at room temperature. The excellent solution-phase and low-temperature processability, self-aligned copper growth, and high electrical conductivity of the Cu/graphene films have permitted fabrication of several electronic circuits on plastic foils, thereby indicating their great potential in compliant, flexible, and printed electronics.
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| 46. |
- Zhao, Jie, et al.
(författare)
-
High-Conductivity Reduced-Graphene-Oxide/Copper Aerogel for Energy Storage
- 2019
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 60, s. 760-767
-
Tidskriftsartikel (refereegranskat)abstract
- This work reports a room-temperature, solution-phase and one-pot method for macro-assembly of a three-dimensional (3D) reduced-graphene-oxide/copper hybrid hydrogel. The hydrogel is subsequently transformed into a highly conductive aerogel via freeze-drying. The aerogel, featuring reduced graphene oxide (rGO) networks decorated with Cu and CuxO nanoparticles (Cu/CuxO@rGO), exhibits a specific surface area of 48 m2/g and an apparent electrical conductivity of ∼33 and ∼430 S/m prior to and after mechanical compression, respectively. The compressed Cu/CuxO@rGO aerogel delivers a specific capacity of ∼453 mAh g−1 at a current density of 1 A/g and ∼184 mAh g−1 at 50 A/g in a 3 M KOH aqueous electrolyte evidenced by electrochemical measurements. Galvanostatic cycling tests at 5 A/g demonstrates that the Cu/CuxO@rGO aerogel retains 38% (∼129 mAh g−1) of the initial capacity (∼339 mAh g−1) after 500 cycles. The straightforward manufacturing process and the promising electrochemical performances make the Cu/CuxO@rGO aerogel an attractive electrode candidate in energy storage applications.
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| 47. |
- Zhao, Jie, et al.
(författare)
-
Microstructure-tunable highly conductive graphene-metal composites achieved by inkjet printing and low temperature annealing
- 2018
-
Ingår i: Journal of Micromechanics and Microengineering. - : IOP PUBLISHING LTD. - 0960-1317 .- 1361-6439. ; 28:3
-
Tidskriftsartikel (refereegranskat)abstract
- We present a method for fabricating highly conductive graphene-silver composite films with a tunable microstructure achieved by means of an inkjet printing process and low temperature annealing. This is implemented by starting from an aqueous ink formulation using a reactive silver solution mixed with graphene nanoplatelets (GNPs), followed by inkjet printing deposition and annealing at 100 degrees C for silver formation. Due to the hydrophilic surfaces and the aid of a polymer stabilizer in an aqueous solution, the GNPs are uniformly covered with a silver layer. Simply by adjusting the content of GNPs in the inks, highly conductive GNP/Ag composites (> 106 S m(-1)), with their microstructure changed from a large-area porous network to a compact film, is formed. In addition, the printed composite films show superior quality on a variety of unconventional substrates compared to its counterpart without GNPs. The availability of composite films paves the way to the metallization in different printed devices, e.g. interconnects in printed circuits and electrodes in energy storage devices.
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