A nano-indentation study of the contact resistance and resistivity of a bi-layered Au/multi-walled carbon nanotube composite

A bi-layer metal-carbon nanotube composite has been developed as a potential low-force electrical contact surface, for application in micro-electromechanical systems switching devices. The samples consist of a vertically aligned forest of multi-walled carbon nanotube (MWCNT), sputter coated with a layer of Au. The effect of varying the components and composition are investigated by means of a modified nano-indenter. By measuring the contact resistance of the composites under various loading conditions, the electrical properties and performance can be evaluated. The composites are shown to have homogenous properties, with each of the layers influencing the total electrical characteristics of the samples. The internal structure of the sample, the MWCNT height and penetration of gold into the forest is shown to directly influence the performance and characteristics of the samples. By analyzing the samples as bulk, the effective resistivities of the composites are also determined to have values from 303 n? m down to 54 n? m, depending on the composition of the sample

Carbon nanotube (CNT) composite surfaces for electrical contact interfaces

MEMS relays boast numerous advantages over PIN diode and FET devices, for example: lower on-resistance, higher isolation and cut-off frequency. There are two common implementations of MEMS switches: capacitively coupled and metal-contacting. Whilst the use of capacitive switches at low frequencies is limited, they tend to be capable of surviving high numbers (&gt;500,000,000) of switching cycles without showing any signs of mechanical failure. For metal-contacting switches, the electrical contacts are mechanically brought into contact without the presence of a dielectric layer on the contacts, consequently enabling the transmission of DC to high frequency signals. A combination of electrical and mechanical factors result in degradation of the contact surfaces over consecutive opening and closing processes which ultimately result in switch failure.The use of gold-coated multi-walled carbon nanotube (Au/MWCNT) bilayer composites have been investigated as a method for improving the reliability of switch contacts. Using a gold-coated MEMS cantilever beam to test the composite contacts. With a load current of 50 mA (load voltage 4 V), the use of a composites contact resulted in a switching lifetime in excess of 44,000,000 hot switching cycles. With a load current of 10 mA, the lifetime is in excess of 500,000,000 cycles. The use of Au/MWCNT composites offer a promising solution to enhance the lifetime of MEMS switches.<br/

Additively Manufactured Graphitic Electrochemical Sensing Platforms

Additive manufacturing (AM)/3D printing technology provides a novel platform for the rapid prototyping of low cost 3D platforms. Herein, we report for the first time, the fabrication, characterisation (physicochemical and electrochemical) and application (electrochemical sensing) of bespoke nanographite (NG)-loaded (25 wt. %) AM printable (via fused deposition modelling) NG/PLA filaments. We have optimised and tailored a variety of NG-loaded filaments and their AM counterparts in order to achieve optimal printability and electrochemical behaviour. Two AM platforms, namely AM macroelectrodes (AMEs) and AM 3D honeycomb (macroporous) structures are benchmarked against a range of redox probes and the simultaneous detection of lead (II) and cadmium (II). This proof-of-concept demonstrates the impact that AM can have within the area of electroanalytical sensors

Additive manufacturing (3D printing) of electrically conductive polymers and polymer nanocomposites and their applications

Additive manufacturing, or three-dimensional (3D) printing, offers a unique solution for fabricating complex geometries with high tolerances. Currently, many commercial additive manufacturing machines focus on the printing of polymers with limited functionalities. However, conductive polymers (CPs) can be processed to enable the additive manufacturing of conductive, low-density, and low-cost parts for a myriad of applications. This review summarizes the relevant achievements in the additive manufacturing of conductive polymers (CPs) and conductive polymer nanocomposites, with a discussion of the advantages and limitations of processing and printing these materials compared with alternative traditional manufacturing methods and their properties. Finally, the prospective applications of these additive manufacturing printed conductive materials are explored

Next-Generation Additive Manufacturing of Complete Standalone Sodium-Ion Energy Storage Architectures

This is the peer reviewed version of the following article: Down, M. P., Martínez-Periñán, E., Foster, C. W., Lorenzo, E., Smith, G. C. & Banks, C. E. (2019). Next-Generation Additive Manufacturing of Complete Standalone Sodium-Ion Energy Storage Architectures. Advanced Energy Materials, 9(11), which has been published in final form at https://doi.org/10.1002/aenm.201803019. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingThe first entirely AM/3D-printed sodium-ion (full-cell) battery is reported herein, presenting a paradigm shift in the design and prototyping of energy- storage architectures. AM/3D-printing compatible composite materials are developed for the first time, integrating the active materials NaMnO2 and TiO2 within a porous supporting material, before being AM/3D- printed into a proof-of-concept model based upon the basic geometry of commercially existing AA battery designs. The freestanding and completely AM/3D-fabricated device demonstrates a respectable performance of 84.3 mAh g-1 with a current density of 8.43 mA g-1; note that the structure is typically comprised of 80% thermoplastic, but yet, still works and functions as an energy-storage platform. The AM/3D-fabricated device is critically benchmarked against a battery developed using the same active materials, but fabricated via a traditional manufacturing method utilizing an ink-based/doctor-bladed methodology, which is found to exhibit a specific capacity of 98.9 mAh m-2 (116.35 mAh g-1). The fabrication of fully AM/3D-printed energy-storage architectures compares favorably with traditional approaches, with the former providing a new direction in battery manufacturing. This work represents a paradigm shift in the technological and design considerations in battery and energy-storage architecture

3D printed graphene based energy storage devices

The final publication is available at Springer via http://dx.doi.org/10.1038/srep422333D printing technology provides a unique platform for rapid prototyping of numerous applications due to its ability to produce low cost 3D printed platforms. Herein, a graphene-based polylactic acid filament (graphene/PLA) has been 3D printed to fabricate a range of 3D disc electrode (3DE) configurations using a conventional RepRap fused deposition moulding (FDM) 3D printer, which requires no further modification/ex-situ curing step. To provide proof-of-concept, these 3D printed electrode architectures are characterised both electrochemically and physicochemically and are advantageously applied as freestanding anodes within Li-ion batteries and as solid-state supercapacitors. These freestanding anodes neglect the requirement for a current collector, thus offering a simplistic and cheaper alternative to traditional Li-ion based setups. Additionally, the ability of these devices’ to electrochemically produce hydrogen via the hydrogen evolution reaction (HER) as an alternative to currently utilised platinum based electrodes (with in electrolysers) is also performed. The 3DE demonstrates an unexpectedly high catalytic activity towards the HER (−0.46 V vs. SCE) upon the 1000th cycle, such potential is the closest observed to the desired value of platinum at (−0.25 V vs. SCE). We subsequently suggest that 3D printing of graphene-based conductive filaments allows for the simple fabrication of energy storage devices with bespoke and conceptual designs to be realised

Covalent targeting of non-cysteine residues in PI4KIIIβ

The synthesis and characterisation of fluorosulfate covalent inhibitors of the lipid kinase PI4KIIIβ is described. The conserved lysine residue located within the ATP binding site was targeted, and optimised compounds based upon reversible inhibitors with good activity and physicochemical profile showed strong reversible interactions and slow onset times for the covalent inhibition, resulting in an excellent selectivity profile for the lipid kinase target. X-Ray crystallography demonstrated a distal tyrosine residue could also be targeted using a fluorosulfate strategy. Combination of this knowledge showed that a dual covalent inhibitor could be developed which reveals potential in addressing the challenges associated with drug resistant mutations

Comparison of sequencing-based methods to profile DNA methylation and identification of monoallelic epigenetic modifications.

Analysis of DNA methylation patterns relies increasingly on sequencing-based profiling methods. The four most frequently used sequencing-based technologies are the bisulfite-based methods MethylC-seq and reduced representation bisulfite sequencing (RRBS), and the enrichment-based techniques methylated DNA immunoprecipitation sequencing (MeDIP-seq) and methylated DNA binding domain sequencing (MBD-seq). We applied all four methods to biological replicates of human embryonic stem cells to assess their genome-wide CpG coverage, resolution, cost, concordance and the influence of CpG density and genomic context. The methylation levels assessed by the two bisulfite methods were concordant (their difference did not exceed a given threshold) for 82% for CpGs and 99% of the non-CpG cytosines. Using binary methylation calls, the two enrichment methods were 99% concordant and regions assessed by all four methods were 97% concordant. We combined MeDIP-seq with methylation-sensitive restriction enzyme (MRE-seq) sequencing for comprehensive methylome coverage at lower cost. This, along with RNA-seq and ChIP-seq of the ES cells enabled us to detect regions with allele-specific epigenetic states, identifying most known imprinted regions and new loci with monoallelic epigenetic marks and monoallelic expression

Next Generation Additive Manufacturing: Tailorable Graphene/Polylactic(acid) Filaments Allow the Fabrication of 3D Printable Porous Anodes for Utilisation within Lithium-Ion Batteries

This is the peer reviewed version of the following article: Foster, C. W., Zou, G., Jiang, Y., Down, M. P., Liauw, C. M., Ferrari, A. G., Ji, X., Smith, G. C., Kellyand, P. J., Banks, C. E. (2019). Next Generation Additive Manufacturing: Tailorable Graphene/Polylactic(acid) Filaments Allow the Fabrication of 3D Printable Porous Anodes for Utilisation within Lithium-Ion Batteries. Batteries & Supercaps., 2(5), 448-453, which has been published in final form at https://doi.org/10.1002/batt.201800148. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingHerein, we report the fabrication and application of Li-ion anodes for utilisation within Li-ion batteries, which are fabricated via additive manufacturing/3D printing (fused depo- sition modelling) using a bespoke graphene/polylactic acid (PLA) filament, where the graphene content can be readily tailored and controlled over the range 1–40 wt. %. We demon- strate that a graphene content of 20 wt. % exhibits sufficient conductivity and critically, effective 3D printability for the rapid manufacturing of 3D printed freestanding anodes (3DAs); simplifying the components of the Li-ion battery negating the need for a copper current collector. The 3DAs are physicochemcally and electrochemically characterised and possess sufficient conductivity for electrochemical studies. Critically, it is found that if the 3DAs are used in Li-ion batteries the specific capacity is very poor but can be significantly improved through the use of a chemical pre-treatment. Such treatment induces an increased porosity, which results in a 200-fold increase (after anode stabilisation) of the specific capacity (ca. 500 mAhg-1 at a current density of 40 mAg-1). This work significantly enhances the field of additive manufacturing/3D printed graphene based energy storage devices demonstrating that useful 3D printable batteries can be realise