New Publication: Novel circuit design for high-impedance and non-local electrical measurements of two-dimensional materials

Fig 1: High-impedance measuring chamber and circuitry. (a) Schematic drawing of the vacuum chamber used to perform the measurements, configured to retrofit a magnet or cryostat. In order to avoid stray capacitance, each SMA connector is wired to the device under test (DUT) using a single-core insulated copper wire. (b) Schematic of the break-out box used to interface the DUT to the measuring instruments. For each BNC connector, it is possible to choose two separate terminals for the shielding (GND1 and GND2), in order to ensure complete floating of the measuring probes. (c) Model of the printed circuit board (PCB) used to mount the DUT. The pins are spaced 5 mm apart to ensure high insulation. (d) Photograph of the actual chamber mounted on an Oxford Instruments Microstat MO superconducting magnet.

Jake Mehew‘s work on an optical isolator circuit which grants access to high-impedance states by electrically decoupling the current-injection from the voltage-sensing circuitry has recently been published in AIP Review of Scientific Instruments: “Two-dimensional materials offer a novel platform for the development of future quantum technologies. However, the electrical characterisation of topological insulating states, non-local resistance, and bandgap tuning in atomically thin materials can be strongly affected by spurious signals arising from the measuring electronics. Common-mode voltages, dielectric leakage in the coaxial cables, and the limited input impedance of alternate-current amplifiers can mask the true nature of such high-impedance states. Here, we present an optical isolator circuit which grants access to such states by electrically decoupling the current-injection from the voltage-sensing circuitry. We benchmark our apparatus against two state-of-the-art measurements: the non-local resistance of a graphene Hall bar and the transfer characteristic of a WS2 field-effect transistor. Our system allows the quick characterisation of novel insulating states in two-dimensional materials with potential applications in future quantum technologies.” See the full article in Review of Scientific Instruments, Volume 89, Issue 2, DOI 10.1063/1.5020044

 

>> See all XM2 publications on www.exeter.ac.uk/metamaterials/research/publications/ <<

 

Riddle time!

In need of a break? Try this for a bit of a change:

Ever played the game Tetris? There’s the possibility to completely clear the board after the first five pieces are placed in a block that’s 10 x 2 squares wide/high. Can you figure out how many different arrangements of Tetris pieces there are to make this happen?

Too easy? Got another one? Please email your riddle suggestions to

The solution to last newsletter’s riddle (I am a three digit number. My second digit is four times more than my third digit. My first digit is seven less than my second digit. What Am I?): 182.

First XM2 PhD thesis submission by Tanveer Tabish: Development of graphene nanostructures for use in anti-cancer nanomedicine

Tanveer Tabish is the first XM2 PGR to submit his PhD thesis (15 February 2018). Please see the abstract of his thesis below. Tanveer is supervised by Shaowei Zhang and Yongde Xia and he published more than 10 journal articles and conference proceedings during his time in the CDT for Metamaterials, for example in the International Journal of Nanomedicine, Nanotechnology, Redox Biology, Scientific Reports, and at the IEEE Nanotechnology Materials and Devices conference (2016), respectively. Tanveer spent 3 months on a research visit at the Politecnico di Milano (Italy) in 2017, and arranged multiple short-term research stays with collaborators at the University of Oxford, King’s College London, and the University of Newcastle. He went to various national and international conferences and workshops, for example in Oxford (UK),  Antalya (Turkey), Toulouse (France) and Chennai (India) where he presented his work via posters and presentations. Tanveer won a presentation prize at the 22nd CSCST-SCI Conference for Renewable energy and novel materials for a sustainable future (Birmingham, 2015) and gave an invited talk on “Fabrication of graphene nanopres for application in marine biology” at a workshop organized by British Council and Royal Society of Chemistry the at the Middle East Technical University in Ankara (Turkey, 2017) .

We are incredibly proud of Tanveer and hope he will be successful with his applications to embark on a career in academia in the UK.

Well done Tanveer!

***

PhD thesis abstract Tanveer Tabish: DEVELOPMENT OF GRAPHENE NANOSTRUCTURES FOR USE IN ANTI-CANCER NANOMEDICINE

 

Figure 1: Schematic illustration of the potential mechanisms by which reactive oxygen species (ROS) are associated with the cellular toxicity of graphene. Graphene may affect biological behavior at the cellular, subcellular, protein and gene levels. The deposition, distribution and clearance of graphene after entering into a living system is a major knowledge gap in understanding the toxicity of graphene. Graphene circulating in the bloodstream is internalized into cells through the plasma membrane. The plasma membrane is a selectively permeable membrane that transfers materials such as ions and nano-sized proteins. Graphene (depending on its size, shape, and surface chemistry) enters the cell via different pathways such as clathrin/caveolar-mediated endocytosis, phagocytosis, macropinocytosis, and pinocytosis and exits the cell via the pathways of lysosome secretion, vesicle-related secretion, and non-vesicle-related secretion. Graphene-induced ROS may cause oxidative stress, loss of cell function, mitochondrial damage, initiation of lipid peroxidation, covalent chemical modifications of nucleic acids, DNA-strand breaks, induction of gene expression via the activation of transcription factors, and modulation of inflammation via signal transduction – leading to toxicity, cell death and genotoxicity.
[With permission of Elsevier, Oxford; ‘Tabish, T. A., Zhang, S., & Winyard, P. G. (2018). Developing the next generation of graphene-based platforms for cancer therapeutics: The potential role of reactive oxygen species. Redox biology. 15, 34-40]
Nanomedicine utilises biocompatible nanomaterials for therapeutic as well as imaging purposes, for the treatment of various diseases including cancer, neurological disorders and wound infections. Graphene, a material composed of a single layer of carbon atoms, has recently shown great potential to improve diagnostics and therapeutics, owing to its small size, large surface-area-to-volume ratio and unique physicochemical properties. However, the limited fabrication, in vitro and in vivo functionalities published in the literature indicate inconsistencies regarding the factors affecting metabolic fate, biodistribution as well as toxicity patterns of graphene. This thesis focuses on the biological effects of graphene-based materials, including graphene oxide (GO), reduced graphene oxide (rGO), graphene nanopores (GNPs), graphene quantum dots (GQDs) and three-dimensional graphene foam (GF). These can be used to closely mimic therapeutic functions and thereby open up new pathways to anticancer nanomedicine. In this work, a biocompatible GO-based anti-metastatic enzyme cancer therapy approach has been introduced for the first time to target the extracellular pro-metastatic and pro- tumourigenic enzymes of cathepsin D and cathepsin L, which are typically overexpressed in ovarian and breast cancers. Definitive binding and modulation of cathepsin- D and -L with GO has revealed that both of the enzymes were adsorbed onto the surface of GO through its cationic and hydrophilic residues under the biologically relevant condition of acidic pH. It has been demonstrated that low concentrations of rGO were shown to significantly produce late apoptosis and necrosis rather than early apoptotic events in lung cancer cells (A549 and SKMES-1), suggesting that it was able to disintegrate the cellular membranes in a dose-dependent manner. GNPs at lower concentrations (250µg/ml) induce upregulation of phosphatidylserine on cell surface membrane (i.e. early apoptotic event), which does not significantly disintegrate the cell membrane in the aforementioned lung cancer cells, while higher concentrations of GNPs (5 and 15 mg/kg) in rats (when intraperitoneally injected) exhibited sub-chronic toxicity in a period of 27 days. The interaction of GQDs and trypsin has revealed the strong bonding capacity of GQDs with trypsin, owing to their surface charge and surface functionalities evidencing the high bioavailability of GQDs in enzyme engineering. Finally, 3D GF was developed to probe the role of graphene-based scaffold cues in the field of regenerative medicine revealing their cell attachment to in vitro cell cultures. Furthermore, GF was shown to maintain remarkable biocompatibility with in vitro and in vivo toxicity screening models when exposed for 7 days at doses of 5, 10 and 15 mg/l. Taken together, graphene and its modified structures developed in this thesis promise to revolutionise clinical settings across the board in nanomedicine which include, but are not limited to, ultra-high sensitive enzyme adsorbents, high throughput biosensors, enzyme modulators and smart scaffolds for tissue regeneration.

XM2 Oversight Board meeting summary

On 13 February 2018 the XM2 Oversight Board (OB) visited us to evaluate the progress our centre has made over the last 6 months.

The day’s agenda saw a few ‘firsts’ as highlights of the day:

  • Prof Alastair Hibbins gave his first talk as Director of the CDT to the OB – an open session to which all supervisors and PGRs were invited;
  • Our first cohort, now approaching graduation, met with the OB to provide feedback on their experiences in the centre over the past 4 years;
  • Our latest intake (2017/18) attended the meeting for the first time – and they did a great job presenting posters of their current work to the Oversight Board.

The OB, the XM2 Management Board (MB) and our Student Advisory Group had an engaged discussion that included ideas about how to best utilise the OB members’ time and experience to the benefit of future PGRs – a proposal following the discussion will be developed together with the student body over the next months. In addition, the PGRs made valuable suggestions on the training elements of the programme which will be taken into consideration for both the current centre and the new proposal.

Overall, the OB’s impressions of the centre’s development (based on the biannual report and communication with PGRs and MB on the day) are rather positive. In particular,  the increase in research outputs and the enhanced profile raising activities (website, blog, CDT videos) to showcase the breadth of our research and the PGRs activities were very well received. A key item of the OB recommendations for future improvement is the engagement of the supervisor body with CDT events and the training progamme. Following sign off of the OB feedback summary we will communicate the details of the recommendations made.

 

 

 

 

 

Training and other events in March 2018

Please see below upcoming trainings, meetings and talks related to the CDT programme.

A final reminder: The next call for Soapbox Science speakers will close on 23rd February 2018. Learn more about Soapbox Science and how to participate.

Date Training/Event Cohort Time Venue
07.03.2018 CDT Group Meeting Group 2 13.30 – 14.30 Har209
09.03.2018 Physics Colloquium: Stuart Mangles – ‘Laser Wakefield Accelerators: a particle accelerator in a university lab?’ All 12.30 – 13.30 Newman Red
13.03.2018 Physics Theory Seminar: David Manolopoulus (title tbc) All 13.30 – 14.30 Physics SCR
14.03.2018 CDT Group Meeting Group 3 13.30 – 14.30 Phy124
16.03.2018 CDT Metamaterials Colloquium: Jaime Gomez Rivas – ‘Surface Lattice Resonances in Arrays of Metallic Particles: From Enhanced Emission to Induced Transparency’ All 12.30 – 13.30 Newman Red
19.03.2018 Presentation Skills workshop 1st Years 10.00 – 12.00 Old Library 4 & 5
21.03.2018 Beyond a PhD: Liz O’Driscoll (title tbc) All 14.00 – 15.30 Laver LT3
23.03.2018 Physics Colloquium: ‘Thermal energy propagation in Si membranes and phononic crystals’ Clivia Sotomayor-Torres All 12.30 – 13.30 Newman Red
28.03.2018 CDT Group Meeting Group 1 12.30 – 13.30 Har209
29.03.2018 Deadline for submission of 6 months project report 1st years  4pm

See February schedule here.

SPIE Photonics West – Our PGRs at the world’s largest photonics technologies event

The XM2 PGRs Joaquin Faneca and Liam Trimby visited San Francisco (California) for one of the biggest events in photonics: the SPIE photonic WEST conference.

Joaquin gave a presentation on his recent research results on integrated 2D materials in silicon nitride platformin in the Silicon Photonic section, and presented a poster in a section devoted to Optical Interconnects. Liam presented a poster summarising his work on tunable metamaterial band-pass filters. Our PGRs appreciated the opportunity to liaise with international representatives from both the scientific and the industry community. The event provided an excellent platform to gain insights in the latest developments of the sector, e.g. outlined in Stephen G. Anderson’s presentation on the strength of the photonics market.

The PGRs also got to enjoy the social and cultural aspects of the conference – from active team work during evening sessions to cycling around the bay and visiting Alcatraz. Joaquin and Liam returned to Exeter being fully enthused by their experience. In Joaquin’s words: “It was simply fantastic!

Julia De Pineda Gutiérrez – the new SAG representative for our second year PGRs

Julia De Pineda Gutiérrez has joined our Student Advisory Group (SAG) to co-represent the 2016 cohort for the remainder of the academic year 2017/18. Zahid Hussain has stepped down due to his extended research stay in Germany.

The Student Advisory Group consists of normally 2 members of each cohort who represent the student body at meetings with the Management and Oversight Boards and the Programme Manager. They help to implement new ideas that benefit the overall experience of their peers, to offer different perspectives, and to ensure the PGRs’ opinions are heard. SAG is currently chaired by Ben Hogan, one of our 3rd year PGRs.

See all SAG representatives and other XM2 PGR ambassadors under http://emps.exeter.ac.uk/metamaterials/about/studentambassadors/

Image taken by Tom Graham (13 Feb 2018)

New Publication: A new class of magnetically actuated pumps and valves for microfluidic applications

has published his latest article on “A new class of magnetically actuated pumps and valves for microfluidic applications” in Scientific Reports in Jan 2018. The research team proposes a new class of magnetically actuated pumps and valves that could be incorporated into microfluidic chips with no further external connections. The idea is to repurpose ferromagnetic low Reynolds number swimmers as devices capable of generating fluid flow, by restricting the swimmers’ translational degrees of freedom. Read more…

Fig: Flow in a Y-shaped channel. The swimmer is pinned at the centre of the junction and the bottom branch of the channel is aligned in parallel to the external magnetic field. The direction of the flow is shown with white arrows. (a) Flow direction in the presence of an applied magnetic field of strength 2.40 mT at a frequency of 60 Hz. (b) Flow direction in the presence of an applied magnetic field of strength 1.38 mT at a frequency of 130 Hz.

>> See all XM2 publications on www.exeter.ac.uk/metamaterials/research/publications/ <<

New Publication: A facile synthesis of porous graphene for efficient water and wastewater treatment

Tanveer Tabish has recently published an article on A facile synthesis of porous graphene for efficient water and wastewater treatment in Nature’s Scientific Reports:

The use of two-dimensional graphene-based materials in water treatment has recently gained significant attention due to their unique electronic and thermal mobility, high surface area, high mechanical strength, excellent corrosion resistance and tunable surface chemistry. However, the relatively expensive, poor hydrophobicity, low adsorption capacity and recyclability, and complex post-treatment of the most pristine graphene frameworks limit their practical application. Here, we report a facile scalable method to produce highly porous graphene from reduced graphene oxide via thermal treatment without addition of any catalyst or use of any template. Read more…

>> See all XM2 publications on www.exeter.ac.uk/metamaterials/research/publications/ <<