| 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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