D.R.S. Cumming

University of Glasgow, Glasgow, Scotland, United Kingdom

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Publications (173)231.23 Total impact

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    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; 15(3). DOI:10.1039/c4lc01153h · 5.75 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). DOI:10.1088/0268-1242/30/1/012001 · 2.21 Impact Factor
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    ABSTRACT: Indium gallium arsenide (InGaAs) planar Gunn diodes with on chip matching circuits were fabricated on a semi-insulating Indium phosphides (InP) substrate. Radial and diamond stub resonators were used as circuit elements to suppress the fundamental frequency and allow the second harmonic frequency to be extracted from the planar Gunn diode. The extraction of the second harmonic will enable the planar Gunn diode to operate at millimetre wave and terahertz frequencies. InGaAs planar Gunn diodes were fabricated with an active channel length (anode to cathode separation) of 4 µm and a width of 120 µm. The experimental results gave a second harmonics signal at 118 GHz with an RF output power of -20 dBm for the radial stub resonator, and 121 GHz with an RF output power of -14.1 dBm for the diamond stub resonator. This is the highest second harmonic power recorded for a planar Gunn diode. The results indicate the potential of terahertz operation by reducing the channel length to sub-micron and extracting the second or third harmonic from the planar Gunn diode.
    ARMMS-Nov-2014, Bedfordshire, United Kingdom; 11/2014
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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). DOI:10.1002/mop.28681 · 0.62 Impact Factor
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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. DOI:10.1016/j.sse.2014.05.011 · 1.51 Impact Factor
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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 08/2014; 61(8):2779-2784. DOI:10.1109/TED.2014.2331368 · 2.36 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: Fluorescence endoscopy is one of the most effective methods for early cancer detection in the GI tract. An endoscopy pill that can provide qualitative and quantitative diagnostic information is required to inspect parts of the GI tract inaccessible to conventional endoscopes. A key component of this pill is an integrated high-sensitivity fluorescence imager with a high voltage source for biasing with very low power consumption. In this paper, we present a power management system for a high sensitivity imager to be integrated in a capsule endoscope for autofluorescence imaging.
    2014 IEEE International Symposium on Circuits and Systems (ISCAS); 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; 14(13). DOI:10.1039/c4lc00436a · 5.75 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 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 03/2014; 115(11):114502-114502-6. DOI:10.1063/1.4868705 · 2.19 Impact Factor
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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. · 3.18 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). DOI:10.1364/OL.39.001227 · 3.18 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]
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    ABSTRACT: A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup.
    Applied Physics Letters 12/2013; 103(24):244103-244103-4. DOI:10.1063/1.4846395 · 3.52 Impact Factor
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    V. Papageorgiou, A. Khalid, J. Grant, C. Li, D. R. S. Cumming
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    ABSTRACT: A new technique is demonstrated for the realisation of air bridges using one lithographic step. Gray scale lithography is used for the formation of 3D profiles on polymethyl methacrylate (PMMA) where a variable dose exposure is applied to create a trapezoid profile for the air bridge. In previous 3D electron beam lithography (EBL) methods the span area was exposed to a low dose or a low acceleration voltage [1,2,3]. Thus, the required discontinuity with the surrounding area for the lift-off process was created. In this technique, no exposure of the span area is needed. Another exposure of a gradient dose is applied to the sides of the highest part of the air bridge. The created profile, after developing the resist, is depicted in Figure 1. The surfaces with red and blue colour represent the metal to form the air bridge and the metal to lift-off, respectively. Using this configuration, the deposited metal at the sides of the top part of the air bridge is connected to the surrounding metal to lift-off and disconnect from the air bridge. The electron dose used in this area has to be smaller than the minimum dose that penetrates the total resist layer, so that the deposited metal does not reach the substrate. This method takes maximum advantage of the resist thickness for the fabrication of high structures, as no part of the resist is sacrificed
    39th International Conference on Micro and Nano Engineering London, UK, September 2013., London; 09/2013
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    ABSTRACT: This work presents the implementation of planar Gunn diodes and pseudomorphic high electron mobility transistors (pHEMTs) on the same wafer for the first time. The AlGaAs/InGaAs/GaAs heterostructures were designed for the realisation of pHEMTs on a Gallium Arsenide - based wafer. T-gate technology has been used for the maximisation of the transistor performance. Devices with a 70 nm long gate foot showed excellent DC and small-signal characteristics, with 780 mS/mm peak transconductance and 200 GHz fmax. Planar Gunn diodes were fabricated in parallel with the pHEMTs, sharing most of the fabrication steps. The diodes produce oscillations with 87.6 GHz maximum frequency and -40 dBm maximum output power.
    ESSDERC 2013 - 43rd European Solid State Device Research Conference; 09/2013
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    ABSTRACT: A self-consistent Ensemble Monte Carlo (EMC) model was developed to simulate the thermionic effect in heterostructure barrier coolers. The model was validated on an InGaAs-InGaAsP heterostructure device of variable barrier height and width, producing good quantitative agreement with previous literature results. The operation of the cooler was found to be a complex and intricate process depending on the field, conduction band and details of barrier structure. When applied to a GaAs-AlGaAs micro-cooler there was good agreement with the experimental results. Importantly, very small alterations in the barrier structure were found to lead to considerable changes in device performance. V C 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4817087]
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    ABSTRACT: An ultrasonic device for micro-patterning and precision manipulation of micrometre-scale particles is demonstrated. The device is formed using eight piezoelectric transducers shaped into an octagonal cavity. By exciting combinations of transducers simultaneously, with a controlled phase delay between them, different acoustic landscapes can be created, patterning micro-particles into lines, squares, and more complex shapes. When operated with all eight transducers the device can, with appropriate phase control, manipulate the two dimensional acoustic pressure gradient; it thus has the ability to position and translate a single tweezing zone to different locations on a surface in a precise and programmable manner.
    2013 IEEE International Ultrasonics Symposium (IUS); 07/2013

Publication Stats

2k Citations
231.23 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
  • 2007
    • University of Aberdeen
      • Department of Physics
      Aberdeen, Scotland, United Kingdom
  • 2006
    • Barcelona Science Park
      Barcino, Catalonia, Spain
  • 2002–2006
    • The University of Edinburgh
      • School of Engineering
      Edinburgh, Scotland, United Kingdom
  • 1992–2004
    • University of Cambridge
      • Centre for Research in Microeconomics
      Cambridge, England, United Kingdom
  • 1999–2003
    • University of Canterbury
      • Department of Electrical and Computer Engineering
      Christchurch, Canterbury, New Zealand