| 1. |
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| 2. |
- Luo, Yifei, et al.
(författare)
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Technology Roadmap for Flexible Sensors
- 2023
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 17:6, s. 5211-5295
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Forskningsöversikt (refereegranskat)abstract
- Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.
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| 3. |
- Lopez Cabezas, Ana, 1980-
(författare)
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Nanofibrillar Materials for Organic and Printable Electronics
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, organic electronics have attracted great attention due to their multiple advantages such as light weight, flexibility, large area fabrication and cost-effective production processes. The recent progress in fabricating organic electronic devices has been achieved with the development of new materials which provide competing functionalities to the electronics devices. However, as it happens with all type of technologies, organic electronics is not free from challenges. In the latest OE-A Roadmap for organic and printed electronics (2011), the “red brick walls” were identified, and the following three main challenges were pointed out as the potential roadblocks from the material point of view: electrical performance, solution processability (especially formulations in non-toxic solvents) and environmental stability. Currently there is a significant increasing interest in optimizing or developing novel materials to meet those requirements. This thesis presents processing development and study of nanofibrillar materials and deals with the optimization for its applicability for organic electronics. The overall work presented in the thesis is based on three nanofibrillar materials: Polyaniline (PANI), carbon nanotubes (CNTs) and the CNT/PANI composite. First, the solution processability of carbon nanotubes and polyaniline is studied respectively, and through covalent and non-covalent methods, stable aqueous dispersions of these materials are successfully achieved. Second, a composite consisting of multi-walled carbon nanotubes (MWCNTs) and PANI with a core-shell structure is developed and characterized. The investigation of the effects of the loading and type of nanotubes incorporated in the composite material, led to understanding on the fundamental theory underlying the composite morphology. Based on those findings and by carefully optimizing the synthesis procedure, water dispersible MWCNT/PANI nanofibrillar composite is successfully synthesized becoming compatible with solution processable techniques, such as spray coating and potentially with printing technology. With the incorporation of carbon nanotubes, the nanofibrillar composite reaches conductivities 20 times higher than that of the pure polymer. Moreover, the presence of the nanotubes in the composite material decelerates up to 60 times the thermal ageing of its conductivity, making the polymer more robust and suitable for possible manufacturing processes. Furthermore, the composite material still retains the advantageous properties of PANI: electrochromism, tunable conductivities, and sensing capabilities. Third, the stable dispersions of PANI, CNTs and MWCNT/PANI composite were effectively deposited by spray coating technique on several low-cost substrates (PET, PEN, polyimide and papers), and homogeneous, flexible, large-area films were fabricated. Additionally, by spraying the materials on pre-fabricated inkjet printed electrodes, a pH sensor based on the MWCNT/PANI composite and a humidity sensor based on functionalized MWCNTs capable of working at GHz range were demonstrated, which shows that the nanofibrillar materials studied in this thesis work are promising sensor materials for wireless application at ultra-high frequency (UHF) band. Finally, the humidity sensor was integrated into a sensor-box demonstrating a hybrid interconnection platform where printed electronics can be seamlessly integrated with silicon-based electronics. The integration closes the gap between the two technologies, anticipating the adaption of organic electronic technologies.
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| 4. |
- Li, Jiantong, 1980-
(författare)
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Ink-jet printing of thin film transistors based on carbon nanotubes
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The outstanding electrical and mechanical properties of single-walled carbon nanotubes (SWCNTs) may offer solutions to realizing high-mobility and high-bendability thin-film transistors (TFTs) for the emerging flexible electronics. This thesis aims to develop low-cost ink-jet printing techniques for high-performance TFTs based on pristine SWCNTs. The main challenge of this work is to suppress the effects of “metallic SWCNT contamination” and improve the device electrical performance. To this end, this thesis entails a balance between experiments and simulations. First, TFTs with low-density SWCNTs in the channel region are fabricated by utilizing standard silicon technology. Their electrical performance is investigated in terms of throughput, transfer characteristics, dimensional scaling and dependence on electrode metals. The demonstrated insensitivity of electrical performance to the electrode metals lifts constrains on choosing metal inks for ink-jet printing. Second, Monte Carlo models on the basis of percolation theory have been established, and high-efficiency algorithms have been proposed for investigations of large-size stick systems in order to facilitate studies of TFTs with channel length up to 1000 times that of the SWCNTs. The Monte Carlo simulations have led to fundamental understanding on stick percolation, including high-precision percolation threshold, universal finite-size scaling function, and dependence of critical conductivity exponents on assignment of component resistance. They have further generated understanding of practical issues regarding heterogeneous percolation systems and the doping effects in SWCNT TFTs. Third, Monte Carlo simulations are conducted to explore new device structures for performance improvement of SWCNT TFTs. In particular, a novel device structure featuring composite SWCNT networks in the channel is predicted by the simulation and subsequently confirmed experimentally by another research group. Through Monte Carlo simulations, the compatibility of previously-proposed long-strip-channel SWCNT TFTs with ink-jet printing has also been demonstrated. Finally, relatively sophisticated ink-jet printing techniques have been developed for SWCNT TFTs with long-strip channels. This research spans from SWCNT ink formulation to device design and fabrication. SWCNT TFTs are finally ink-jet printed on both silicon wafers and flexible Kapton substrates with fairly high electrical performance.
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| 5. |
- Xie, Yuan, et al.
(författare)
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Wnt signaling regulates MFSD2A-dependent drug delivery through endothelial transcytosis in glioma
- 2023
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Ingår i: Neuro-Oncology. - : Oxford University Press. - 1522-8517 .- 1523-5866. ; 25:6, s. 1073-1084
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Tidskriftsartikel (refereegranskat)abstract
- Background: Systemic delivery of anti-tumor therapeutic agents to brain tumors is thwarted by the blood-brain barrier (BBB), an organotypic specialization of brain endothelial cells (ECs). A failure of pharmacological compounds to cross BBB is one culprit for the dismal prognosis of glioblastoma (GBM) patients. Identification of novel vascular targets to overcome the challenges posed by the BBB in tumors for GBM treatment is urgently needed.Methods: Temozolomide (TMZ) delivery was investigated in CT2A and PDGFB-driven RCAS/tv-a orthotopic glioma models. Transcriptome analysis was performed on ECs from murine gliomas. Mfsd2a deficient, Cav1 deficient, and Mfsd2a EC-specific inducible mice were developed to study the underlying molecular mechanisms.Results: We demonstrated that inhibiting Wnt signaling by LGK974 could increase TMZ delivery and sensitize glioma to chemotherapy in both murine glioma models. Transcriptome analysis of ECs from murine gliomas revealed that Wnt signaling inhibition enhanced vascular transcytosis as indicated by the upregulation of PLVAP and downregulation of MFSD2A. Mfsd2a deficiency in mice enhances TMZ delivery in tumors, whereas constitutive expression of Mfsd2a in ECs suppresses the enhanced TMZ delivery induced by Wnt pathway inhibition in murine glioma. In addition, Wnt signaling inhibition enhanced caveolin-1 (Cav1)-positive caveolae-mediated transcytosis in tumor ECs. Moreover, Wnt signaling inhibitor or Mfsd2a deficiency fails to enhance TMZ penetration in tumors from Cav1-deficient mice.Conclusions: These results demonstrated that Wnt signaling regulates MFSD2A-dependent TMZ delivery through a caveolae-mediated EC transcytosis pathway. Our findings identify Wnt signaling as a promising therapeutic target to improve drug delivery for GBM treatment.
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| 6. |
- Li, Shiyu, 1991-
(författare)
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Engineering Surfaces of Solid-State Nanopores for Biomolecule Sensing
- 2021
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Nanopores have emerged as a special class of single-molecule analytical tool that offers immense potential for sensing and characterizing biomolecules such as nucleic acids and proteins. As an alternative to biological nanopores, solid-state nanopores present remarkable versatility due to their wide-range tunability in pore geometry and dimension as well as their excellent mechanical robustness and stability. However, being intrinsically incompatible with biomolecules, surfaces of inorganic solids need be modified to provide desired functionalities for real-life sensing purposes. In this thesis, we presented an exploration of various surface engineering strategies and an examination of several surface associated phenomena pertaining specifically to solid-state nanopores. Based on the parallel sensing concept using arrayed pores, optical readout is mainly employed throughout the whole study.For the surface engineering aspect, a list of approaches was explored. A versatile surface patterning strategy for immobilization of biomolecules was developed based on selective poly(vinylphosphonic acid) passivation and electron beam induced deposition technique. This scheme was then implemented on nanopore arrays for nanoparticle localization. In addition, vesicle rupture-based lipid bilayer coating was adapted to truncated-pyramidal nanopores, which was shown to be effective for the minimizing DNA-pore interaction. Further, HfO2 coating by means of atomic layer deposition was employed to prevent the erosion of Si-based pores and to shrink the pore diameter, which enabled reliable investigations of DNA clogging and DNA polymerase docking.For the surface associated phenomena, several findings were made. The lipid bilayer formation on truncated pyramidal nanopores via instantaneous rupture of individual vesicles was quantified based on combined ionic current monitoring and optical observation. The probability of pore clogging appeared to linearly increase with the length of DNA strands and applied bias voltage, which could be attributed a higher probability of knotting and/or folding of longer DNA strands and more frequent translocation events at higher voltage. A free-energy based analytical model was proposed to evaluate the DNA-pore interaction and to interpret observed clogging behavior. Finally, docking of DNA polymerase on nanopore arrays was demonstrated using label-free optical method based on Ca2+ indicator dyes, which may open the avenue to sequencing-by-synthesis enabled by the docked polymerase.
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| 7. |
- Luo, Jun, 1979-
(författare)
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Integration of metallic source/drain contacts in MOSFET technology
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The continuous and aggressive downscaling of conventional CMOS devices has been driving the vast growth of ICs over the last few decades. As the CMOS downscaling approaches the fundamental limits, novel device architectures such as metallic source/drain Schottky barrier MOSFET (SB-MOSFET) and SB-FinFET are probably needed to further push the ultimate downscaling. The ultimate goal of this thesis is to integrate metallic Ni1-xPtx silicide (x=0~1) source/drain into SB-MOSFET and SB-FinFET, with an emphasis on both material and processing issues related to the integration of Ni1-xPtx silicides towards competitive devices. First, the effects of both carbon (C) and nitrogen (N) on the formation and on the Schottky barrier height (SBH) of NiSi are studied. The presence of both C and N is found to improve the poor thermal stability of NiSi significantly. The present work also explores dopant segregation (DS) using B and As for the NiSi/Si contact system. The effects of C and N implantation into the Si substrate prior to the NiSi formation are examined, and it is found that the presence of C yields positive effects in helping reduce the effective SBH to 0.1-0.2 eV for both conduction polarities. In order to unveil the mechanism of SBH tuning by DS, the variation of specific contact resistivity between silicide and Si substrates by DS is monitored. The formation of a thin interfacial dipole layer at silicide/Si interface is confirmed to be the reason of SBH modification. Second, a systematic experimental study is performed for Ni1-xPtx silicide (x=0~1) films aiming at the integration into SB-MOSFET. A distinct behavior is found for the formation of Ni silicide films. Epitaxially aligned NiSi2-y films readily grow and exhibit extraordinary morphological stability up to 800 oC when the thickness of deposited Ni (tNi) <4 nm. Polycrystalline NiSi films form and tend to agglomerate at lower temperatures for thinner films for tNi≥4 nm. Such a distinct annealing behavior is absent for the formation of Pt silicide films with all thicknesses of deposited Pt. The addition of Pt into Ni supports the above observations. Surface energy is discussed as the cause responsible for the distinct behavior in phase formation and morphological stability. Finally, three different Ni-SALICIDE schemes towards a controllable NiSi-based metallic source/drain process without severe lateral encroachment of NiSi are carried out. All of them are found to be effective in controlling the lateral encroachment. Combined with DS technology, both n- and p-types of NiSi source/drain SB-MOSFETs with excellent performance are fabricated successfully. By using the reproducible sidewall transfer lithography (STL) technology developed at KTH, PtSi source/drain SB-FinFET is also realized in this thesis. With As DS, the characteristics of PtSi source/drain SB-FinFET are transformed from p-type to n-type. This thesis work places Ni1-xPtx (x=0~1) silicides SB-MOSFETs as a competitive candidate for future CMOS technology.
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| 8. |
- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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| 9. |
- Sahu, Siddharth S., 1994-
(författare)
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Detection of Bio-analytes with Streaming Current : From Fundamental Principles to Novel Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A biosensor based on streaming current is a new and relatively unexplored subject with significant potential. This thesis attempts to gain a deeper understanding of the governing principles, and then exploit them to further improve its performance as well as develop novel applications. To this end, the underlying theoretical frameworks were examined and two critical parameters of the target: its size and electric charge, influencing the sensor’s sensitivity were identified. This was followed by experimental evaluation of the parameters, using a set of tailor-made proteins, aiming to understand the nature and extent of their influence on the sensor response in relation to simulation performed following an established model.The dependence of the sensor response on the charge of an analyte, or specifically the charge contrast between the sensor surface and an analyte, opens a new avenue to improve the sensitivity and also to develop novel functionality. First, this aspect was exploited to improve the sensitivity by optimizing the surface functionalization strategy. Three such methods were compared in terms of the resulting zeta potential of the surface. The sensitivity was the highest when the charge contrast was maximum. The optimal functionalization strategy was then used for highly sensitive detection of extracellular vesicles (EVs), where an improvement in the limit of detection by two orders of magnitude over the previously reported results was demonstrated. Two applications of the improved method were then demonstrated: monitoring the effectiveness of targeted cancer medicines and analysis of liquid biopsy of cancer patients via sensitive profiling of EV-membrane proteins.Improvement in the detection specificity is a critical aspect of biosensing. This was achieved by implementing a sandwich immunoassay and demonstrating the proof of concept using trastuzumab as the target and Z-domain as both the capture and detection probes. Although the improved selectivity came at the cost of a lower sensitivity, this could be mitigated via DNA-conjugation with the detection probes, a novel electrostatic labelling strategy that allows for improvement of the sensitivity by exploiting the electrostatic influence. An application of this method was then demonstrated by detecting the target from a complex medium of E. coli cell lysate. Continuing the prospect of charge engineering of antibodies, a set of positively and negatively charged antibodies were synthesized by conjugating poly-lysine and DNA oligonucleotides, respectively. This enabled stepwise, multiplexed membrane protein analysis of EVs using the alternating charge-labelled antibodies. The method was then applied to investigate EV-heterogeneity.
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| 10. |
- Zhao, Jie
(författare)
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Solution-Processable Conductive Graphene-Based Materials for Flexible Electronics
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis work explores electrical conductors based on few-layer graphene flakes as an enabler for low-cost, mechanically flexible, and high-conductivity conductors in large area flexible and printed electronic devices. The flakes are deposited from aqueous solutions and processed at low temperature.Graphene is selected for its excellent properties in mechanical, optical, electronic, and electrical aspects. However, thin films of pristine few-layer graphene flakes deposited from dispersions normally exhibit inferior electrical conductivity. One cause responsible for this problem is the loose stacking and random orientation of graphene flakes in a graphene deposition. We have solved this problem by implementing a simple post-deposition treatment leading to dramatically densified and planarized thin films. Significantly increased electrical conductivity by ~20 times is obtained. The 1-pyrenebutyric acid tetrabutylammonium salt as an exfoliation enhancer and dispersant in water yields ~110 S/m in conductivity when the graphene based thin films are processed at 90 °C. In order to achieve higher conductivity, a room-temperature method for site-selective copper electroless deposition has been developed. This method is of particular interest for the self-aligned copper deposition to the predefined graphene films. The resultant two-layer graphene/copper structure is characterized by an overall conductivity of ~7.9 × 105 S/m, an increase by ~7000 times from the template graphene films. Several electronic circuits based on the graphene/copper bilayer interconnect have been subsequently fabricated on plastic foils as proof-of-concept demonstrators. Alternatively, highly conductive composites featuring graphene flakes coated with silver nanoparticles with electrical conductivity beyond 106 S/m can be readily obtained at 100 oC. Moreover, a highly conductive reduced-graphene-oxide/copper hybrid hydrogel has been achieved by mixing aqueous graphene oxide solution and copper-containing Fehling's solution. The corresponding aerogel of high porosity exhibits an apparent electrical conductivity of ~430 S/m and delivers a specific capacity of ~453 mAh g−1 at current density of 1 A/g. The experimental results presented in this thesis show that the solution-phase, low-temperature fabrication of highly conductive graphene-based materials holds promises for flexible electronics and energy storage applications.
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| 11. |
- Chen, Xi
(författare)
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Silicon Nanowire Field-Effect Devices as Low-Noise Sensors
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the past decades, silicon nanowire field-effect transistors (SiNWFETs) have been explored for label-free, highly sensitive, and real-time detections of chemical and biological species. The SiNWFETs are anticipated for sensing analyte at ultralow concentrations, even at single-molecule level, owing to their significantly improved charge sensitivity over large-area FETs. In a SiNWFET sensor, a change in electrical potential associated with biomolecular interactions in close proximity to the SiNW gate terminal can effectively control the underlying channel and modulate the drain-to-source current (IDS) of the SiNWFET. A readout signal is therefore generated. This signal is primarily determined by the surface properties of the sensing layer on the gate terminal, with sensitivity close up to the Nernstian limit widely demonstrated. To achieve a high signal-to-noise ratio (SNR), it is essential for the SiNWFETs to possess low noise of which intrinsic device noise is one of the major components. In metal-oxide-semiconductor (MOS)-type FETs, the intrinsic noise mainly results from carrier trapping/detrapping at the gate oxide/semiconductor interface and it is inversely proportional to the device area.This thesis presents a comprehensive study on design, fabrication, and noise reduction of SiNWFET-based sensors on silicon-on-oxide (SOI) substrate. A novel Schottky junction gated SiNWFET (SJGFET) is designed and experimentally demonstrated for low noise applications. Firstly, a robust process employing photo- and electron-beam mixed-lithography was developed to reliably produce sub-10 nm SiNW structures for SiNWFET fabrication. For a proof-of-concept demonstration, MOS-type SiNWFET sensors were fabricated and applied for multiplexed ion detection using ionophore-doped mixed-matrix membranes as sensing layers. To address the fundamental noise issue of the MOS-type SiNWFETs, SJGFETs were fabricated with a Schottky (PtSi/silicon) junction gate on the top surface of the SiNW channel, replacing the noisy gate oxide/silicon interface in the MOS-type SiNWFETs. The resultant SJGFETs exhibited a close-to-ideal gate coupling efficiency (60 mV/dec) and significantly reduced device noise compared to reference MOS-type SiNWFETs. Further optimization was performed by implementing a three-dimensional Schottky junction gate wrapping both top surface and two sidewalls of the SiNW channel. The tri-gate SJGFETs with optimized geometry exhibited significantly enhanced electrostatic control over the channel, thereby confined IDS in the SiNW bulk, which greatly improved the device noise immunity to the traps at bottom buried oxide/silicon interface. Finally, a lateral bipolar junction transistor (LBJT) was also designed and fabricated on a SOI substrate aiming for immediate sensor current amplification. Integrating SJGFETs with LBJTs is expected to significantly suppress environmental interference and improve the overall SNR especially under low sensor current situations.
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| 12. |
- Hinnemo, Malkolm, 1986-
(författare)
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On the Road to Graphene Biosensors
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biosensors are devices that detect biological elements and then transmit a readable signal. Biosensors can automatize diagnostics that would otherwise have to be performed by a physician or perhaps not be possible to perform at all. Current biosensors are however either limited to particular diseases or prohibitively expensive. In order to further the field, sensors capable of many parallel measurements at a lower cost need to be developed. Field effect transistor (FET) based sensors are possible candidates for delivering this, mainly by allowing miniaturization. Smaller sensors could be cheaper, and enable parallel measurements.Graphene is an interesting material to use as the channel of FET-sensors. The low electrochemical reactivity of its plane makes it possible to have graphene in direct contact with the sample liquid, which enhances the signal from impedance changes. Graphene-FET based impedance sensors should be able to sense almost all possible analytes and allow for scaling without losing sensitivity.In this work the steps needed to make graphene based biosensors are presented. An improved graphene transfer is described which by using low pressure to dry the graphene removes most contamination. A method to measure the contamination of graphene by surface enhanced Raman scattering is presented. Methods to produce double gated and electrolyte gated graphene transistors on a large scale in an entirely photolithographic process are detailed. The deposition of 1-pyrenebutyric acid (PBA) on graphene is studied. It is shown that at high surface concentrations the PBA stands up on graphene and forms a dense self-assembled monolayer. A new process of using Raman spectroscopy data to quantify adsorbents was developed in order to quantify the molecule adsorption. Biosensing has been performed in two different ways. Graphene FETs have been used to read the signal generated by a streaming potential setup. Using FETs in this context enables a more sensitive readout than what would be possible without them. Graphene FETs have been used to directly sense antibodies in high ionic strength. This sensing was done by measuring the impedance of the interface between the FET and the electrolyte.
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| 13. |
- Hu, Qitao
(författare)
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Silicon Nanowire Based Electronic Devices for Sensing Applications
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Silicon nanowire (SiNW) based electronic devices fabricated with a complementary metal-oxide-semiconductor (CMOS) compatible process have wide-range and promising applications in sensing area. These SiNW sensors own high sensitivity, low-cost mass production possibility, and high integration density. In this thesis, we design and fabricate SiNW electronic devices with the CMOS-compatible process on silicon-on-insulator (SOI) substrates and explore their applications for ion sensing and quantum sensing. The thesis starts with ion sensing using SiNW field-effect transistors (SiNWFETs). The specific interaction between a sensing layer and analyte generates a change of local charge density and electrical potential, which can effectively modulate the conductance of SiNW channel. Multiplexed detection of molecular (MB+) and elemental (Na+) ions is demonstrated using a SiNWFET array, which is functionalized with ionophore-incorporated mixed-matrix membranes (MMMs). As a follow-up, polyethylene glycol (PEG) doping strategy is explored to suppress interference from the hydrophobic molecular ion and expand the multiplexed detection range. Then, the SiNW is downscaled to sub-10 nm with a gate-oxide-free configuration for single charge detection in liquid. We directly observe the capture and emission of a single H+ ion with individually activated Si dangling bonds (DBs) on the SiNW surface. This work demonstrates the unprecedented ability of the sub-10 nm SiNWFET for investigating the physics of the solid/liquid interface at single charge level.Apart from ion sensing, the SiNWFET can be suspended and act as a nanoelectromechanical resonator aiming for electrically detecting potential quantized mechanical vibration at low temperature. A suspended SiNW based single-hole transistor (SHT) is explored as a nanoelectromechanical resonator at 20 mK. Mechanical vibration is transduced to electrical readout by the SHT, and the transduction mechanism is dominated by piezoresistive effect. A giant effective piezoresistive gauge factor (~6000) with a strong correlation to the single-hole tunneling is also estimated. This hybrid device is demonstrated as a promising system to investigate macroscopic quantum behaviors of vibration phonon modes.Noise, including intrinsic device noise and environmental interference, is a serious concern for sensing applications of SiNW electronic devices. A H2 annealing process is explored to repair the SiNW surface defects and thus reduce the intrinsic noise by one order of magnitude. To suppress the external interference, lateral bipolar junction transistors (LBJTs) are fabricated on SOI substrate for local signal amplification of the SiNW sensors. Current gain and overall signal-to-noise ratio of the LBJTs are also optimized with an appropriate substrate voltage.
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| 14. |
- Lind, Lars, et al.
(författare)
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Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)
- 2021
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Ingår i: eLife. - : eLife Sciences Publications Ltd. - 2050-084X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions.
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| 15. |
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| 16. |
- Shi, Peng, et al.
(författare)
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Age- and gender-specific trends in respiratory outpatient visits and diagnoses at a tertiary pediatric hospital in China : a 10-year retrospective study
- 2020
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Ingår i: BMC Pediatrics. - : BioMed Central. - 1471-2431. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Respiratory infections are one of three leading causes of childhood mortality, and worldwide increase and recent plateau in childhood asthma has been reported. However, data on trends of respiratory diseases over long period of time is limited. This study aimed to determine the trends of respiratory disease outpatient visits (ROVs) and diagnoses (RODs) in one of the largest children's teaching hospitals in China between 2009 and 2018.METHODS: A retrospective study based on routine administrative data was designed and implemented according to the RECORD statement. Demographic details and diagnoses of the outpatients < 18 years visiting the respiratory department of the hospital were extracted from the Hospital Information System. Age- and gender-specific trends were illustrated by calculating average annual growth rate (AAGR) for ROVs and comparing change of proportion for different RODs over time.RESULTS: There were 698,054 ROVs from 285,574 children (40.4% female). AAGR of ROVs was 15.2%. Children aged 4 to < 7 years had a faster increase than other age groups. Bronchitis (27.6%), pneumonia (18.5%), pneumonia affecting other systems (18.4%), asthma and status asthmaticus (10.7%), and vasomotor and allergic rhinitis (9.2%) accounted for 84.4% of all RODs. The proportion of bronchitis decreased across years, with the concomitant increasing trend in the proportion of pneumonia. Age-specific trend in diagnoses showed greater proportion of asthma in all visits for the children aged 7 to < 18 years than younger children. Gender-specific trend in diagnoses showed the proportion of asthma was greater for males but the AAGR was greater for females.CONCLUSION: The persistent upward trend in ROVs was observed among children at different ages and a gender difference was also seen. In contrast to what has been reported, burden of asthma and allergies diseases continues to increase locally.
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| 17. |
- Wen, Chenyu
(författare)
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Solid-State Nanopores for Sensing : From Theory to Applications
- 2019
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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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| 18. |
- Zhang, Zhen, 1979-
(författare)
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Integration of silicide nanowires as Schottky barrier source/drain in FinFETs
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The steady and aggressive downscaling of the physical dimensions of the conventional metal-oxide-semiconductor field-effect-transistor (MOSFET) has been the main driving force for the IC industry and information technology over the past decades. As the device dimensions approach the fundamental limits, novel double/trigate device architecture such as FinFET is needed to guarantee the ultimate downscaling. Furthermore, Schottky barrier source/drain technology presents a promising solution to reducing the parasitic source/drain resistance in the FinFET. The ultimate goal of this thesis is to integrate Schottky barrier source/drain in FinFETs, with an emphasis on process development and integration towards competitive devices. First, a robust sidewall transfer lithography (STL) technology is developed for mass fabrication of Si-nanowires in a controllable manner. A scalable self-aligned silicide (SALICIDE) process for Pt-silicides is also developed. Directly accessible and uniform NWs of Ni- and Pt-silicides are routinely fabricated by combining STL and SALICIDE. The silicide NWs are characterized by resistivity values comparable to those of their thin–film counterparts. Second, a systematic experimental study is performed for dopant segregation (DS) at the PtSi/Si and NiSi/Si interfaces in order to modulate the effective SBHs needed for competitive FinFETs. Two complementary schemes SIDS (silicidation induced dopant segregation) and SADS (silicide as diffusion source) are compared, and both yield substantial SBH modifications for both polarities of Schottky diodes (i.e. φbn and φbp). Third, Schottky barrier source/drain MOSFETs are fabricated in UTB-SOI. With PtSi that is usually used as the Schottky barrier source/drain for p-channel SB-MOSFETs, DS with appropriate dopants leads to excellent performance for both types of SBMOSFETs. However, a large variation in position of the PtSi/Si interface with reference to the gate edge (i.e., underlap) along the gate width is evidenced by TEM. Finally, integration of PtSi NWs in FinFETs is carried out by combining the STL technology, the Pt-SALICIDE process and the DS technology, all developed during the course of this thesis work. The performance of the p-channel FinFETs is improved by DS with B, confirming the SB-FinFET concept despite device performance fluctuations mostly likely due to the presence of the PtSi-to-gate underlap.
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| 19. |
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| 20. |
- Luo, Dan, et al.
(författare)
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Green, General and Low-cost Synthesis of Porous Organic Polymers in Sub-kilogram Scale for Catalysis and CO2 Capture
- 2023
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Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- Porous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large-scale production. Herein, we report the synthesis of imine and aminal-linked POPs using inexpensive diamine and dialdehyde monomer in green solvents. Theoretical calculations and control experiments show that using meta-diamines is crucial for forming aminal linkages and branching porous networks from [2 + 2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub-kilogram quantities at a relatively low cost. Proof-of-concept studies demonstrate that the POPs can be used as high-performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost-effective approach for large-scale synthesis of various POPs.
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| 21. |
- Taddei, C, et al.
(författare)
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Repositioning of the global epicentre of non-optimal cholesterol
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 582:7810, s. 73-
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Tidskriftsartikel (refereegranskat)abstract
- High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol—which is a marker of cardiovascular risk—changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million–4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.
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| 22. |
- Wang, Yuanbo, et al.
(författare)
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Prediction of urban airflow fields around isolated high-rise buildings using data-driven non-linear correction models
- 2023
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Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323 .- 1873-684X. ; 246
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Tidskriftsartikel (refereegranskat)abstract
- When it comes to predicting urban airflow, steady Reynolds-averaged Navier-Stokes (SRANS) models that rely on Reynolds stress often face a challenge called the closure problem. This problem involves unresolved structural flaws and uncertainties in the closure coefficients used in the models. Previous attempts to recalibrate coefficients for specific urban flows without breaking the linear constitutive relation have resulted in simulation results constrained by the baseline turbulence model. Therefore, this study aims to enhance the performance of SRANS models by addressing these structural flaws. To achieve this, a novel data-driven framework is proposed. It leverages the deterministic symbolic regression algorithm to discover explicit algebraic expressions for a non-linear Reynolds stress correction model. The robustness of the correction model is ensured by maintaining the linear eddy viscosity model for iterative calculations while keeping the non-linear component frozen. The proposed framework is evaluated using three isolated building cases with varying geometric configurations and inflow boundary conditions. Findings demonstrate that computational fluid dynamics (CFD) predictions incorporating the data-driven non-linear correction model consistently align closer to wind tunnel experimental results compared to both standard and non-linear versions of the k-ε turbulence model. This improvement is reflected in reduced reattachment lengths and more accurate mean velocity distributions in the wake of buildings. However, it should be noted that there is a possibility of overpredicting wind velocity in the windward area. This study introduces valuable insights and additional strategies to enhance the prediction accuracy of SRANS models in urban airflow simulations.
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