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Journal articleYong S, Yao C, Hillier N, et al., 2024,
Ti3C2 MXene as additive for low‐cost textile supercapacitors with enhanced electrical performance
, Advanced Materials Technologies, Vol: 9, ISSN: 2365-709XTextile-based energy storage components are paramount for establishing invisible electronic textiles that do not require conventional rigid batteries. A novel and scalable fabrication method is reported for introducing MXene (Ti3C2Tx) into activated carbon (AC) supercapacitors to enhance electrochemical performance. Supercapacitors are prepared within a single layer of textile with a phase-inverted polymer membrane fabricated within the textile yarn structure to form a porous, flexible, and mechanically durable separator. MXene is introduced in two different forms: 1) A multilayer MXene (m-MXene)powder is mechanically mixed with an AC slurry and deposited onto the textile. 2) Delaminated MXene (d-Mxene) nanosheets are spray-coated onto the surface of spray coated AC electrode. With an organic electrolyte, 1 M tetraethylammonium tetrafluoroborate in dimethyl sulfoxide, these supercapacitors are electrochemically stable between +/− 2.6 V and demonstrate a maximum areal capacitance of 148.7 mF cm−2, an energy density of 0.921 mWh cm−2, and a power density of 1.01 mW cm−2. The addition of MXenes improves the areal capacitance and by combining both approaches an improvement of 220% is achieved compared with identical supercapacitors with standard AC electrodes. The novelty of this work is to develop a scalable and straightforward solution processing method for introducing MXene into carbon supercapacitor electrodes enabling high-performance textile-based energy storage devices.
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Journal articleYong S, Yao C, Hillier N, et al., 2024,
Ti3C2 MXene as additive for low-cost textile supercapacitors with enhanced electrical performance
, Advanced Materials Technologies, Vol: 9, ISSN: 2365-709XTextile-based energy storage components are paramount for establishing invisible electronic textiles that do not require conventional rigid batteries. A novel and scalable fabrication method is reported for introducing MXene (Ti3C2Tx) into activated carbon (AC) supercapacitors to enhance electrochemical performance. Supercapacitors are prepared within a single layer of textile with a phase-inverted polymer membrane fabricated within the textile yarn structure to form a porous, flexible, and mechanically durable separator. MXene is introduced in two different forms: 1) A multilayer MXene (m-MXene)powder is mechanically mixed with an AC slurry and deposited onto the textile. 2) Delaminated MXene (d-Mxene) nanosheets are spray-coated onto the surface of spray coated AC electrode. With an organic electrolyte, 1 M tetraethylammonium tetrafluoroborate in dimethyl sulfoxide, these supercapacitors are electrochemically stable between +/− 2.6 V and demonstrate a maximum areal capacitance of 148.7 mF cm−2, an energy density of 0.921 mWh cm−2, and a power density of 1.01 mW cm−2. The addition of MXenes improves the areal capacitance and by combining both approaches an improvement of 220% is achieved compared with identical supercapacitors with standard AC electrodes. The novelty of this work is to develop a scalable and straightforward solution processing method for introducing MXene into carbon supercapacitor electrodes enabling high-performance textile-based energy storage devices.
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Journal articleZhang X, Tan W, Carey T, et al., 2023,
Enhanced composite thermal conductivity by percolated networks of in-situ confined-grown carbon nanotubes
, Nano Research, Vol: 16, Pages: 12821-12829, ISSN: 1998-0000Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry, nanomaterials like carbon nanotubes (CNTs) have been constrained by the nonuniform dispersion and difficulty in constructing effective three-dimensional (3D) conduction network with low loading and desired isotropic or anisotropic (specific preferred heat conduction) performances. Herein, we illustrated the in-situ construction of CNT based 3D heat conduction networks with different directional performances. First, to in-situ construct an isotropic percolated conduction network, with spherical cores as support materials, we developed a confined-growth technique for CNT-core sea urchin (CNTSU) materials. With 21.0 wt.% CNTSU loading, the thermal conductivity of composites reached 1.43 ± 0.13 W/(m·K). Secondly, with aligned hexagonal boron nitride (hBN) as an anisotropic support, we constructed CNT-hBN aligned networks by in-situ CNT growth, which improved the utilization efficiency of high density hBN and reduced the thermal interface resistance between matrix and fillers. With ~ 8.5 wt.% loading, the composites possess thermal conductivity up to 0.86 ± 0.14 W/(m·K), 374% of that for neat matrix. Due to the uniformity of CNTs in hBN network, the synergistic thermal enhancement from one-dimensional (1D) + two-dimensional (2D) hybrid materials becomes more distinct. Based on the detailed experimental evidence, the importance of purposeful production of a uniformly interconnected heat conduction 3D network with desired directional performance can be observed, particularly compared with the traditional direct-mixing method. This study opens new possibilities for the preparation of high-power-density electronics packaging and interfacial materials when both directional thermal performance and complex composite geometry are simultaneously required.
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Journal articleWang T, Hopper T, Mondal N, et al., 2023,
Hot carrier cooling and trapping in atomically thin WS₂ probed by three-pulse femtosecond spectroscopy
, ACS Nano, Vol: 17, Pages: 6330-6340, ISSN: 1936-0851Transition metal dichalcogenides (TMDs) have shown outstanding semiconducting properties which make them promising materials for next-generation optoelectronic and electronic devices. These properties are imparted by fundamental carrier–carrier and carrier–phonon interactions that are foundational to hot carrier cooling. Recent transient absorption studies have reported ultrafast time scales for carrier cooling in TMDs that can be slowed at high excitation densities via a hot-phonon bottleneck (HPB) and discussed these findings in the light of optoelectronic applications. However, quantitative descriptions of the HPB in TMDs, including details of the electron–lattice coupling and how cooling is affected by the redistribution of energy between carriers, are still lacking. Here, we use femtosecond pump–push–probe spectroscopy as a single approach to systematically characterize the scattering of hot carriers with optical phonons, cold carriers, and defects in a benchmark TMD monolayer of polycrystalline WS2. By controlling the interband pump and intraband push excitations, we observe, in real-time (i) an extremely rapid “intrinsic” cooling rate of ∼18 ± 2.7 eV/ps, which can be slowed with increasing hot carrier density, (ii) the deprecation of this HPB at elevated cold carrier densities, exposing a previously undisclosed role of the carrier–carrier interactions in mediating cooling, and (iii) the interception of high energy hot carriers on the subpicosecond time scale by lattice defects, which may account for the lower photoluminescence yield of TMDs when excited above band gap.
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Journal articleFenech-Salerno B, Holicky M, Yao C, et al., 2023,
A sprayed graphene transistor platform for rapid and low-cost chemical sensing
, Nanoscale, Vol: 15, Pages: 3243-3254, ISSN: 2040-3364We demonstrate a novel and versatile sensing platform, based on electrolyte-gated graphene field-effect transistors, for easy, low-cost and scalable production of chemical sensor test strips. The Lab-on-PCB platform is enabled by low-boiling, low-surface-tension sprayable graphene ink deposited on a substrate manufactured using a commercial printed circuit board process. We demonstrate the versatility of the platform by sensing pH and Na+ concentrations in an aqueous solution, achieving a sensitivity of 143 ± 4 μA per pH and 131 ± 5 μA per log10Na+, respectively, in line with state-of-the-art graphene chemical sensing performance.
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Journal articleLatham KG, Edathil AA, Rezaei B, et al., 2022,
Challenges and opportunities in free-standing supercapacitors research
, APL Materials, Vol: 10, Pages: 1-14, ISSN: 2166-532XThe design of commercial supercapacitors has remained largely unchanged since the 1970s, comprising powdered electrodes housed in rigid metal cylinders or pouches. To power the next generation of integrated technologies, an evolution in supercapacitor materials and design is needed to create multifunctional materials that allow energy storage while imparting additional material properties (e.g., flexibility and strength). Conductive free-standing electrodes produced from fibers or 3D printed materials offer this opportunity as their intrinsic mechanical properties can be transferred to the supercapacitor. Additionally, their conductive nature allows for the removal of binders, conductive agents, and current collectors from the supercapacitor devices, lowering their economic and environmental cost. In this Perspective, we summarize the recent progress on free-standing supercapacitors from new methods to create free-standing electrodes to novel applications for these devices, together with a detailed discussion and analysis on their electrochemical performance and physicochemical and mechanical properties. Furthermore, the potential directions and prospects of future research in developing free-standing supercapacitors are proposed.
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Journal articleKim H, Arbab A, Fenech Salerno B, et al., 2022,
Barium titanate-enhanced hexagonal boron nitride inks for printable high-performance dielectrics
, Nanotechnology, Vol: 33, Pages: 1-8, ISSN: 0957-4484Printed electronics have been attracting significant interest for their potential to enable flexible and wearable electronic applications. Together with printable semiconductors, solution processed dielectric inks are key in enabling low-power and high-performance printed electronics. In the quest for suitable dielectrics inks, two-dimensional materials such as hexagonal boron nitride (h-BN) have emerged in the form of printable dielectrics. In this work, we report barium titanate (BaTiO3) nanoparticles as an effective additive for inkjet-printable h-BN inks. The resulting inkjet printed h-BN/BaTiO3 thin films reach a dielectric constant (εr) of ~ 16 by adding 10% of BaTiO3 nanoparticles (in their volume fraction to the exfoliated h-BN flakes) in water-based inks. This result enabled all-inkjet printed flexible capacitors with C ~ 10.39 nF cm-2, paving the way to future low power, printed and flexible electronics.
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Journal articleSpanu A, Mascia A, Baldazzi G, et al., 2022,
Parylene C-based, breathable tattoo electrode for high-quality biopotential measurements
, Frontiers in Bioengineering and Biotechnology, Vol: 10, Pages: 1-15, ISSN: 2296-4185A breathable tattoo electrode for bio-potential recording based on a Parylene C nanofilm is presented in this study. The proposed approach allows for the fabrication of micro-perforated epidermal submicrometer-thick electrodes that conjugate the unobtrusiveness of Parylene C nanofilms and the very important feature of breathability. The electrodes were fully validated for electrocardiography (ECG) measurements showing performance comparable to that of conventional disposable gelled Ag/AgCl electrodes, with no visible negative effect on the skin even many hours after their application. This result introduces interesting perspectives in the field of epidermal electronics, particularly in applications where critical on-body measurements are involved.
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Journal articlePiatti E, Arbab A, Galanti F, et al., 2021,
Charge transport mechanisms in inkjet-printed thin-film transistors based on two-dimensional materials
, Nature Electronics, Vol: 4, Pages: 893-905, ISSN: 2520-1131Printed electronics using inks based on graphene and other two-dimensional materials can be used to create large-scale, flexible, and wearable devices. However, the complexity of the ink formulations, and the polycrystalline nature of the resulting thin films, have made it difficult to examine charge transport in such devices. Here we report the charge transport mechanisms of surfactant- and solvent-free inkjet-printed thin-film devices based on few-layer graphene (semi-metal), molybdenum disulfide (MoS2, semiconductor) and titanium carbide MXene (Ti3C2, metal) by investigating the temperature, gate and magnetic field dependencies of their electrical conductivity. We find that charge transport in printed few-layer MXene and MoS2 devices is dominated by the intrinsic transport mechanism of the constituent flakes: MXene exhibits a weakly-localized 2D metallic behaviour at any temperature, whereas MoS2 behaves as an insulator with a crossover from 3D-Mott variable-range hopping to nearest-neighbour hopping around 200 K. Charge transport in printed few-layer graphene devices is dominated by the transport mechanism between different flakes, which exhibit 3D-Mott variable range hopping conduction at any temperature.
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Journal articleBohm S, Ingle A, Bohm M, et al., 2021,
Graphene production by cracking
, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 379, Pages: 1-14, ISSN: 1364-503Xn recent years, graphene has found its use in numerous industrial applications due to its unique properties. While its impermeable and conductive nature can replace currently used anticorrosive toxic pigments in coating systems, due to its large strength to weight ratio, graphene can be an important component as a next-generation additive for automotive, aerospace & construction applications. The current bottlenecks in using graphene & graphene oxide and other 2D materials are the availability of cost-effective, high-quality materials and their effective incorporation (functionalisation and dispersion)into the product matrices. On overcoming these factors, graphene may attract significant demands in terms of volume consumption. Graphene can be produced on industrial scales and cost-effective top-down routes such as chemical, electro chemical, and/or high-pressure mechanical exfoliation. Graphene depending on end applications can be chemically tuned and modified via functionalisation so that easy incorporation into product matrices is possible. This paper discusses different production methods and their impact on the quality of graphene produced in terms of energy input. Graphene with an average thickness below five layers were produced by both methods with varied defects. However, a higher yield of graphene with a lower number of layers was produced by the high-pressure exfoliation route.
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Journal articleSeyedin S, Carey T, Arbab A, et al., 2021,
Fibre electronics: towards scaled-up manufacturing of integrated e-textile systems
, Nanoscale, Vol: 13, Pages: 12818-12847, ISSN: 2040-3364The quest for a close human interaction with electronic devices for healthcare, safety, energy and security has driven giant leaps in portable and wearable technologies in recent years. Electronic textiles (e-textiles) are emerging as key enablers of wearable devices. Unlike conventional heavy, rigid, and hard-to-wear gadgets, e-textiles can lead to lightweight, flexible, soft, and breathable devices, which can be worn like everyday clothes. A new generation of fibre-based electronics is emerging which can be made into wearable e-textiles. A suite of start-of-the-art functional materials have been used to develop novel fibre-based devices (FBDs), which have shown excellent potential in creating wearable e-textiles. Recent research in this area has led to the development of fibre-based electronic, optoelectronic, energy harvesting, energy storage, and sensing devices, which have also been integrated into multifunctional e-textile systems. Here we review the key technological advancements in FBDs and provide an updated critical evaluation of the status of the research in this field. Focusing on various aspects of materials development, device fabrication, fibre processing, textile integration, and scaled-up manufacturing we discuss current limitations and present an outlook on how to address the future development of this field. The critical analysis of key challenges and existing opportunities in fibre electronics aims to define a roadmap for future applications in this area.
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Journal articleHui F, Liu P, Hodge S, et al., 2021,
In-situ observation of low-power nano-synaptic response in graphene oxide using conductive atomic force microscopy
, Small, Vol: 17, ISSN: 1613-6810Multiple studies have reported the observation of electro-synaptic response in different metal/insulator/metal devices; however, most of them analysed large (>1 µm2) devices that do not meet the integration density required by the industry (1010 devices/mm2). Some studies employed a scanning tunnelling microscope (STM) to explore nano-synaptic response in different materials, but in this setup there is a nanogap between the insulator and one of the metallic electrodes (i.e. the STM tip), which is not present in real devices. Here we show how to use a conductive atomic force microscope (CAFM) to explore the presence and quality of nano-synaptic response in confined areas <500 nm2. For this study, we selected graphene oxide (GO) due to its easy fabrication and excellent electrical properties. Our experiments indicate that metal/GO/metal nano-synapses exhibit potentiation and paired pulse facilitation with low write current levels <1 µA (i.e. power consumption ~3 μW), controllable excitatory post-synaptic currents and long-term potentiation and depression. Our results provide a new method to explore nano-synaptic plasticity at the nanoscale, and point GO as an important candidate material for the fabrication of ultra-small (<500 nm2) electronic synapses fulfilling the integration density requirements of neuromorphic systems.
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Journal articleLund A, Wu Y, Fenech-Salerno B, et al., 2021,
Conducting materials as building blocks for electronic textiles
, Materials Research Society (MRS) Bulletin, Vol: 46, Pages: 491-501, ISSN: 0883-7694To realize the full gamut of functions that are envisaged for electronic textiles (e-textiles) a range of semiconducting, conducting and electrochemically active materials are needed. This article will discuss how metals, conducting polymers, carbon nanotubes, and two-dimensional (2D) materials, including graphene and MXenes, can be used in concert to create e-textile materials, from fibers and yarns to patterned fabrics. Many of the most promising architectures utilize several classes of materials (e.g., elastic fibers composed of a conducting material and a stretchable polymer, or textile devices constructed with conducting polymers or 2D materials and metal electrodes). While an increasing number of materials and devices display a promising degree of wash and wear resistance, sustainability aspects of e-textiles will require greater attention.
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Journal articleCarey T, Arbab A, Anzi L, et al., 2021,
Inkjet printed circuits with 2D semiconductor inks for high-performance electronics
, Advanced Electronic Materials, ISSN: 2199-160XAir-stable semiconducting inks suitable for complementary logic are key to create low-power printed integrated circuits (ICs). High-performance printable electronic inks with 2D materials have the potential to enable the next generation of high performance low-cost printed digital electronics. Here, the authors demonstrate air-stable, low voltage (<5 V) operation of inkjet-printed n-type molybdenum disulfide (MoS2), and p-type indacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors (FETs), estimating an average switching time of τMoS2 ≈ 4.1 μs for the MoS2 FETs. They achieve this by engineering high-quality MoS2 and air-stable IDT-BT inks suitable for inkjet-printing complementary pairs of n-type MoS2 and p-type IDT-BT FETs. They then integrate MoS2 and IDT-BT FETs to realize inkjet-printed complementary logic inverters with a voltage gain |Av| ≈ 4 when in resistive load configuration and |Av| ≈ 1.4 in complementary configuration. These results represent a key enabling step towards ubiquitous long-term stable, low-cost printed digital ICs.
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Journal articleSergioli G, Militello C, Rundo L, et al., 2021,
A quantum-inspired classifier for clonogenic assay evaluations
, SCIENTIFIC REPORTS, Vol: 11, ISSN: 2045-2322- Author Web Link
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Conference paperJahin M, Fenech-Salerno B, Moser N, et al., 2021,
Detection of <i>MGMT</i> methylation status using a Lab-on-Chip compatible isothermal amplification method
, 43rd Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (IEEE EMBC), Publisher: IEEE, Pages: 7385-7389, ISSN: 1557-170X -
Journal articleMezzapesa FP, Garrasi K, Schmidt J, et al., 2020,
Terahertz frequency combs exploiting an on-chip, solution-processed, graphene-quantum cascade laser coupled-cavity
, ACS Photonics, Vol: 7, Pages: 3489-3498, ISSN: 2330-4022The ability to engineer quantum-cascade-lasers (QCLs) with ultrabroad gain spectra, and with a full compensation of the group velocity dispersion, at terahertz (THz) frequencies, is key for devising monolithic and miniaturized optical frequency-comb-synthesizers (FCSs) in the far-infrared. In THz QCLs four-wave mixing, driven by intrinsic third-order susceptibility of the intersubband gain medium, self-locks the optical modes in phase, allowing stable comb operation, albeit over a restricted dynamic range (∼20% of the laser operational range). Here, we engineer miniaturized THz FCSs, comprising a heterogeneous THz QCL, integrated with a tightly coupled, on-chip, solution-processed, graphene saturable-absorber reflector that preserves phase-coherence between lasing modes, even when four-wave mixing no longer provides dispersion compensation. This enables a high-power (8 mW) FCS with over 90 optical modes, through 55% of the laser operational range. We also achieve stable injection-locking, paving the way to a number of key applications, including high-precision tunable broadband-spectroscopy and quantum-metrology.
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Journal articleJi X, Liu W, Yin Y, et al., 2020,
A graphene-based electro-thermochromic textile display
, Journal of Materials Chemistry C, Vol: 8, Pages: 15788-15794, ISSN: 2050-7526Electronic textiles (e textiles) are rapidly emerging as key enablers for wearable electronics. Graphene and 2D materials have played a major role in enabling truly wearable e-textiles. Here we demonstrate a textile-based display using the Joule's heating of a screen-printed, few-layer graphene ink to drive the colour switching of thermochromic polyurethane on a cotton fabric. The average temperature of the few-layer graphene ink on the fabric was voltage-controlled reaching about 43 °C in 45 s at a bias of 12 V and a recovery of <20 s with negligible degradation after several heating/cooling cycles. This is used to demonstrate several electro-thermochromic textile displays, thus representing a breakthrough in e-textiles technology.
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Working paperCarey T, Arbab A, Anzi L, et al., 2020,
Inkjet printed circuits with two-dimensional semiconductor inks for high-performance electronics
, Publisher: arXivAir-stable semiconducting inks suitable for complementary logic are key tocreate low-power printed integrated circuits (ICs). High-performance printableelectronic inks with two-dimensional materials have the potential to enable thenext generation of high performance, low-cost printed digital electronics. Herewe demonstrate air-stable, low voltage (< 5 V) operation of inkjet-printedn-type molybdenum disulfide (MoS2) and p-typeindacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors(FETs), estimating a switching time of {\tau} ~ 3.3 {\mu}s for the MoS2 FETs.We achieve this by engineering high-quality MoS2 and air-stable IDT-BT inkssuitable for inkjet-printing complementary pairs of n-type MoS2 and p-typeIDT-BT FETs. We then integrate MoS2 and IDT-BT FETs to realise inkjet-printedcomplementary logic inverters with a voltage gain |Av| ~ 4 when in resistiveload configuration and |Av| ~ 1.36 in complementary configuration. Theseresults represent a key enabling step towards ubiquitous long-term stable,low-cost printed digital ICs.
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Journal articleSchütt F, Zapf M, Signetti S, et al., 2020,
Conversionless efficient and broadband laser light diffusers for high brightness illumination applications
, Nature Communications, Vol: 11, Pages: 1-10, ISSN: 2041-1723Laser diodes (LDs) are considered the next generation of ultra-efficient light sources. However, state-of-the-art LD-based lighting systems rely on light-converting phosphorous materials, which strongly limit the efficiency, lifetime as well as the achievable light output due to energy losses, saturation, thermal degradation and low irradiance levels. Here, we demonstrate a macroscopically expanded, three-dimensional diffuser composed of interconnected hollow hexagonal boron nitride microtubes with nanoscopic wall-thickness, acting as an artificial solid fog, capable of withstanding ~10 times the irradiance level of remote phosphors. Indeed, in contrast to phosphors, no light conversion is required as the diffuser relies solely on strong broadband (full visible range) lossless multiple light scattering events, enabled by a highly porous (> 99.99%) non-absorbing nanoarchitecture, resulting in efficiencies of up to 98 %. This can unleash the potential of lasers for high-brightness lighting applications, such as automotive headlights, projection technology or lighting for large spaces.
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