D.R.S. Cumming

University of Glasgow, Glasgow, Scotland, United Kingdom

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Publications (236)363.35 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Advances in diagnostics, cell and stem cell technologies drive the development of application-specific tools for cell and particle separation. Acoustic micro-particle separation offers a promising avenue for high-throughput, label-free, high recovery, cell and particle separation and isolation in regenerative medicine. Here, we demonstrate a novel approach utilizing a dynamic acoustic field that is capable of separating an arbitrary size range of cells. We first demonstrate the method for the separation of particles with different diameters between 6 and 45 μm and secondly particles of different densities in a heterogeneous medium. The dynamic acoustic field is then used to separate dorsal root ganglion cells. The shearless, label-free and low damage characteristics make this method of manipulation particularly suited for biological applications. Advantages of using a dynamic acoustic field for the separation of cells include its inherent safety and biocompatibility, the possibility to operate over large distances (centimetres), high purity (ratio of particle population, up to 100%), and high efficiency (ratio of separated particles over total number of particles to separate, up to 100%).
    Lab on a Chip 12/2014; · 5.70 Impact Factor
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    ABSTRACT: An experimental method has been used to estimate the dead space of planar Gunn diodes which were fabricated using GaAs and InP based materials, respectively. The experimental results indicate that the dead space was approximately 0.23 μm and the saturation domain velocity 0.96 × 105 m s−1 for an Al0.23Ga0.77As based device, while for an In0.53Ga0.47As based device, the dead space was approximately 0.21 μm and the saturation domain velocity 1.93 × 105 m s−1. Further, the results suggest that the saturation domain velocity is reduced or there is an increase in the dead-space due to local field distortions when the active channel length of the planar Gunn diode is less than 1 micron.
    Semiconductor Science and Technology 11/2014; 30(1). · 1.92 Impact Factor
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    ABSTRACT: Miniature aluminium gallium arsenide/gallium arsenide (AlGaAs/GaAs) coolers were fabricated on wafer, enabling different contact geometries to be realized in the same process run. To individually DC bias the microcooler, microprobes were used leading to thermal loading of the cooler. A simple experimental technique was developed to verify the temperature difference (ΔT) between the cold cathode and hot anode contacts is due to cooling rather than heating of the cooler. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2699–2700, 2014
    Microwave and Optical Technology Letters 11/2014; 56(11). · 0.59 Impact Factor
  • Ivonne Escorcia Carranza, James Grant, David R.S. Cumming
    39th International Conference on Infrared, Millimeter, and Terahertz Waves, Tucson, AZ; 09/2014
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    ABSTRACT: Planar Indium Gallium Arsenide (InGaAs) Gunn diodes with on chip matching circuits have been fabricated on a semi-insulating Indium Phosphide (InP) substrate to enable the extraction of the second harmonic in millimeter-wave and terahertz frequencies. The planar Gunn diodes were designed in coplanar waveguide (CPW) format with an active length of 4 µm and width 120 µm integrated to CPW matching circuit and radial stub resonator to suppress the fundamental and extract the second harmonic. Initial experimental measurements have shown good fundamental suppression (-35.2 dBm) and extraction of power (-19dBm) at the second harmonic frequency (117GHz).
    Solid-State Electronics 09/2014; 99:38-40. · 1.48 Impact Factor
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    ABSTRACT: This work presents two different approaches for the implementation of pseudomorphic high electron mobility transistors (pHEMTs) and planar Gunn diodes on the same gallium arsenide substrate. In the first approach, a combined wafer is used where a buffer layer separates the active layers of the two devices. A second approach was also examined using a single wafer where the AlGaAs/InGaAs/GaAs heterostructures were designed for the realisation of pHEMTs. The comparison between the two techniques showed that the devices fabricated on the single pHEMT wafer presented superior performance over the combined wafer technique. The DC and small-signal characteristics of the pHEMTs on the single wafer were enhanced after the use of T-gates with 70 nm length. The maximum transconductance of the transistors was equal to 780 mS/mm with 200 GHz maximum frequency of oscillation (fmax). Planar Gunn diodes fabricated in the pHEMT wafer, with 1.3 μm anode-to-cathode separation (LAC) presented oscillations at 87.6 GHz with maximum power of oscillation equal to −40 dBm.
    Solid-State Electronics 07/2014; · 1.48 Impact Factor
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    ABSTRACT: We have designed, simulated and fabricated multi-spectral materials operating in visible, near infrared and terahertz wavebands by combining plasmonic filters with metamaterials. Multi-spectral materials offer a path to the creation of co-axial multi-spectral imagers.
    CLEO: Science and Innovations; 06/2014
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    ABSTRACT: Accurate control over positioning of cells is a highly desirable feature in tissue engineering applications since it allows, for example, population of substrates in a controlled fashion, rather than relying on random seeding. Current methods to achieve a differential distribution of cells mostly use passive patterning methods to change chemical, mechanical or topographic properties of surfaces, making areas differentially permissive to the adhesion of cells. However, these methods have no ad hoc control over the actual deposition of cells. Direct patterning methods like bioprinting offer good control over cell position, but require sophisticated instrumentation and are often cost- and time-intensive. Here, we present a novel electronically controlled method of generating dynamic cell patterns by acoustic trapping of cells at a user-determined position, with a heptagonal acoustic tweezer device. We demonstrate the capability of the device to create complex patterns of cells using the device's ability to re-position acoustic traps by using a phase shift in the acoustic wave, and by switching the configuration of active piezoelectric transducers. Furthermore, we show that by arranging Schwann cells from neonatal rats in a linear pattern we are able to create Bands of Büngner-like structures on a non-structured surface and demonstrate that these features are able to guide neurite outgrowth from neonatal rat dorsal root ganglia.
    Lab on a Chip 05/2014; · 5.70 Impact Factor
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    ABSTRACT: We present, for the first time, the fabrication process for a submicron planar Gunn diode in In0.53Ga0.47As on an InP substrate operating at 265 GHz. A novel two stage lift off method has been developed to achieve a submicron gaps between contacts down to 135 nm with widths up to 120 μm.
    2014 26th International Conference on Indium Phosphide and Related Materials (IPRM); 05/2014
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    ABSTRACT: The length of the transit region of a Gunn diode determines the natural frequency at which it operates in fundamental mode—the shorter the device, the higher the frequency of operation. The long-held view on Gunn diode design is that for a functioning device the minimum length of the transit region is about 1.5 lm, limiting the devices to fundamental mode operation at frequencies of roughly 60 GHz. Study of these devices by more advanced Monte Carlo techniques that simulate the ballistic transport and electron-phonon interactions that govern device behaviour, offers a new lower bound of 0.5 lm, which is already being approached by the experimental evidence that has shown planar and vertical devices exhibiting Gunn operation at 600 nm and 700 nm, respectively. The paper presents results of the first ever THz submicron planar Gunn diode fabricated in In 0.53 Ga 0.47 As on an InP substrate, operating at a fundamental frequency above 300 GHz. Experimentally measured rf power of 28 lW was obtained from a 600 nm long  120 lm wide device. At this new length, operation in fundamental mode at much higher frequencies becomes possible—the Monte Carlo model used predicts power output at frequencies over 300 GHz. V C 2014 AIP Publishing LLC.
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    J Grant, I J H McCrindle, C Li, D R S Cumming
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    ABSTRACT: We present the simulation, implementation, and measurement of a multispectral metamaterial absorber (MSMMA) and show that we can realize a simple absorber structure that operates in the mid-IR and terahertz (THz) bands. By embedding an IR metamaterial absorber layer into a standard THz metamaterial absorber stack, a narrowband resonance is induced at a wavelength of 4.3 μm. This resonance is in addition to the THz metamaterial absorption resonance at 109 μm (2.75 THz). We demonstrate the inherent scalability and versatility of our MSMMA by describing a second device whereby the MM-induced IR absorption peak frequency is tuned by varying the IR absorber geometry. Such a MSMMA could be coupled with a suitable sensor and formed into a focal plane array, enabling multispectral imaging.
    Optics Letters 03/2014; 39(5):1227-30. · 3.39 Impact Factor
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    J. Grant, I. J. H. McCrindle, C. Li, D. R. S. Cumming
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    ABSTRACT: We present the simulation, implementation, and measurement of a multispectral metamaterial absorber (MSMMA) and show that we can realize a simple absorber structure that operates in the mid-IR and terahertz (THz) bands. By embedding an IR metamaterial absorber layer into a standard THz metamaterial absorber stack, a narrowband resonance is induced at a wavelength of 4.3 μm. This resonance is in addition to the THz metamaterial absorption resonance at 109 μm (2.75 THz). We demonstrate the inherent scalability and versatility of our MSMMA by describing a second device whereby the MM-induced IR absorption peak frequency is tuned by varying the IR absorber geometry. Such a MSMMA could be coupled with a suitable sensor and formed into a focal plane array, enabling multispectral imaging.
    Optics Letters 02/2014; 39(5). · 3.39 Impact Factor
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    ABSTRACT: A novel gallium arsenide (GaAs) based micro-cooler design, previously analysed both experimentally and by an analytical Heat Transfer (HT) model, has been simu-lated using a self-consistent Ensemble Monte Carlo (EMC) model for a more in depth analysis of the thermionic cooling in the device. The best fit to the experimental data was found and was used in conjunction with the HT model to estimate the cooler-contact resistance. The cooling results from EMC indicated that the cooling power of the device is highly dependent on the charge distribution across the leading inter-face. Alteration of this charge distribution via interface extensions on the nanometre scale has shown to produce significant changes in cooler performance. C 2014 Au-thor(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4865251]
  • V. Papageorgiou, A. Khalid, C. Li, D.R.S. Cumming
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    ABSTRACT: We present the cofabrication of planar Gunn diodes and high-electron mobility transistors (HEMTs) on an indium phosphide substrate for the first time. Electron beam lithography has been used extensively for the complete fabrication procedure and a 70-nm T-gate technology was incorporated for the enhancement of the small-signal characteristics of the HEMT. Diodes with anode-to-cathode separation ( (L_{rm ac}) ) down to 1- and 120- (mu ) m width were shown to oscillate up to 204 GHz. The transistor presents a cutoff frequency ( (f_{_{T}}) ) of 220 GHz, with power gain up to 330 GHz ( (f_{max }) ). The integration of the two devices creates the potential for the realization of high-power, high-frequency MMIC Gunn oscillators, circuits, and systems.
    IEEE Transactions on Electron Devices 01/2014; 61(8):2779-2784. · 2.06 Impact Factor
  • David R S Cumming, Stephen B Furber, Douglas J Paul
    Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 01/2014; 372(2012):20130376. · 2.89 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The length of the transit region of a Gunn diode determines the natural frequency at which it operates in fundamental mode—the shorter the device, the higher the frequency of operation. The long-held view on Gunn diode design is that for a functioning device the minimum length of the transit region is about 1.5 μm, limiting the devices to fundamental mode operation at frequencies of roughly 60 GHz. Study of these devices by more advanced Monte Carlo techniques that simulate the ballistic transport and electron-phonon interactions that govern device behaviour, offers a new lower bound of 0.5 μm, which is already being approached by the experimental evidence that has shown planar and vertical devices exhibiting Gunn operation at 600 nm and 700 nm, respectively. The paper presents results of the first ever THz submicron planar Gunn diode fabricated in In0.53Ga0.47As on an InP substrate, operating at a fundamental frequency above 300 GHz. Experimentally measured rf power of 28 μW was obtained from a 600 nm long × 120 μm wide device. At this new length, operation in fundamental mode at much higher frequencies becomes possible—the Monte Carlo model used predicts power output at frequencies over 300 GHz.
    Journal of Applied Physics 01/2014; 115(11):114502-114502-6. · 2.21 Impact Factor
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    ABSTRACT: Wirelessly directed nerve regeneration: inductively powered electrical stimulation circuits on the biodegradable polymer, polycaprolactone, demonstrate directed regeneration of sensory neurons from a dorsal root ganglion. These circuits, produced using a unique transfer printing process, illustrate progress towards the use of electrical stimulation systems on biodegradable materials to improve peripheral nerve repair functional outcomes.
    Advanced Healthcare Materials 12/2013;
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    Advanced Optical Materials. 11/2013;
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    ABSTRACT: In this article a monolithic resonant terahertz sensor element with a noise equivalent power superior to that of typical commercial room temperature single pixel terahertz detectors and capable of close to real time read-out rates is presented. The detector is constructed via the integration of a metamaterial absorber and a micro-bolometer sensor. An absorption magnitude of 57% at 2.5 THz, a minimum NEP of and a thermal time constant of 68 ms for the sensor are measured. As a demonstration of detector capability, it is employed in a practical Nipkow terahertz imaging system. The monolithic resonant terahertz detector is readily scaled to focal plane array formats by adding standard read-out and addressing circuitry enabling compact, low-cost terahertz imaging.
    Laser & Photonics Review 11/2013; 7(6). · 7.98 Impact Factor
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    Chong Li, James Grant, Jue Wang, David R S Cumming
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    ABSTRACT: We present a novel Nipkow disk design for terahertz (THz) single pixel imaging applications. A 100 mm high resistivity (ρ≈3k-10k Ω·cm) silicon wafer was used for the disk on which a spiral array of twelve 16-level binary Fresnel lenses were fabricated using photolithography and a dry-etch process. The implementation of Fresnel lenses on the Nipkow disk increases the THz signal transmission compared to the conventional pinhole-based Nipkow disk by more than 12 times thus a THz source with lower power or a THz detector with lower detectivity can be used. Due to the focusing capability of the lenses, a pixel resolution better than 0.5 mm is in principle achievable. To demonstrate the concept, a single pixel imaging system operating at 2.52 THz is described.
    Optics Express 10/2013; 21(21):24452-9. · 3.55 Impact Factor

Publication Stats

1k Citations
363.35 Total Impact Points

Institutions

  • 1995–2014
    • University of Glasgow
      • • School of Engineering
      • • Division of Electronics and Electrical Engineering
      Glasgow, Scotland, United Kingdom
  • 2010
    • Chinese Academy of Sciences
      Peping, Beijing, China
  • 2006
    • University of Liverpool
      • School of Biological Sciences
      Liverpool, ENG, United Kingdom
    • Barcelona Science Park
      Barcino, Catalonia, Spain
  • 2002–2005
    • The University of Edinburgh
      Edinburgh, Scotland, United Kingdom
  • 1999–2003
    • University of Canterbury
      • Department of Electrical and Computer Engineering
      Christchurch, Canterbury, New Zealand
  • 1992–1993
    • University of Cambridge
      • • Centre for Research in Microeconomics
      • • Department of Physics: Cavendish Laboratory
      Cambridge, England, United Kingdom