Greg Bridges

Greg Bridges
University of Manitoba | UMN · Department of Electrical and Computer Engineering

PhD

About

219
Publications
17,124
Reads
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2,212
Citations
Additional affiliations
January 1989 - February 2016
University of Manitoba
Position
  • Professor

Publications

Publications (219)
Article
Dry food commodities like grains and pulses can be stored safely for several years under controlled storage conditions. The equilibrium moisture content of the packaged grain is one of the most important parameters required to be monitored and controlled for extended safe storage. This paper presents a single element dual-polarized sensing tag base...
Article
Full-text available
The perfect absorption of electromagnetic waves has promoted many applications, including photovoltaics, radar cloaking, and molecular detection. Unlike conventional methods of critical coupling that require asymmetric boundaries or coherent perfect absorption that require multiple coherent incident beams, here we demonstrate single-beam perfect ab...
Article
Food waste amounts to roughly one-third of its total production every year. There is an unprecedented demand to improve long-term storage of food products while preserving quality and safety in every stage of its processing, from postharvesting to preconsumption. Different technologies, such as total viable count (TVC), metal-oxide-semiconductor se...
Article
The dielectric properties of biological cells can be used to gain information on their physiology and morphology. This paper reports the first measurements of the dielectric spectra of viable and non-viable cells over the full beta-dispersion (interfacial) frequency range. Dielectrophoresis (DEP) single cell in-flow techniques were employed to quan...
Article
In this work, we present an optical transit dielectrophoresis (DEP) flow cytometer for parallel single‐cell analysis. Each cell's dielectric property is inferred from velocity perturbations due to DEP actuation in a microfluidic channel. Dual LED sources facilitate velocity measurement by producing two transit shadows for each cell passing through...
Article
Acoustic pulse-echo systems, are effective for corrosion damage detection in buried individual ground rods without any need for excavation. In electric power distribution systems there are large numbers buried ground rods are used in substations to form a grounding networks that is critical for the protection of equipment and personnel working in t...
Article
The ability to monitor the status of cells during nutrient limitation is important for optimizing bioprocess growth conditions in batch and fed‐batch cultures. The activity level of Na+/K+ ATPase pumps and cytoplasm ionic concentrations are directly influenced by the nutrient level, and thus, cytoplasm conductivity can be used as a marker‐less indi...
Article
The dielectric properties of cells are directly related to their morphological and physiological properties and can be used to monitor their status when exposed to stress conditions. In this work, dual-frequency dielectrophoresis (DEP) cytometry was employed to measure changes in the membrane capacitance and cytoplasm conductivity of single Chinese...
Chapter
Dielectric measurement techniques such as impedance spectroscopy and dielectrophoresis methods have been employed to study biological phenomena based on the intrinsic electrical properties of cells and their sub-compartments (membrane capacitance and conductance, cytosol conductivity, etc.). They are label-free and non-invasive and have shown promi...
Article
Full-text available
Abstract In mammalian cells cytoplasm ion concentrations and hence cytoplasm conductivity is an important indicator of their physiological state. Changes in the cytoplasm conductivity has been associated with physiological changes such as progression of cancer and apoptosis. In this work, a model that predicts the effects of physiological changes i...
Article
Dielectrophoresis (DEP) cytometry was used to investigate changes in the membrane capacitance, membrane conductance, and cytoplasm conductivity of single Chinese hamster ovary (CHO) cells subjected to thermal stress. CHO cells were exposed to temperatures ranging from 37 °C to 50 °C for 15 min and measured immediately after exposure. Heat-treated c...
Article
Nutrient depletion in fed-batch cultures and at the end of batch cultures is among the main causes of stress on cells and a trigger of apoptosis. In this study, we investigated changes in the cytoplasm conductivity of Chinese hamster ovary (CHO) cells under controlled starvation. Employing a single-cell dielectrophoresis (DEP) cytometer, we measure...
Article
Full-text available
Applying sufficiently strong pulsed electric fields to a cell can permeabilize the membrane and subsequently affect its dielectric properties. In this study, we employ a microfluidicdielectrophoresis cytometry technique to simultaneously electroporate and measure the time-dependent dielectric response of single Chinese hamster ovary cells. Using ex...
Conference Paper
This paper presents a stacked multiple coil design for simultaneous multi-parameter narrow-band sensing with RLC-type near-field coupled resonators. The resonant frequency and Q-factor of each RLC sensor is dependent on change of stored energy and loss in response to the parameter of interest. One challenge with these types of sensors is mutual cou...
Article
Full-text available
We present a dielectric model and its parameters for Chinese hamster ovary (CHO) cells based on a double-shell structure which includes the cell membrane, cytoplasm, nuclear envelope, and nucleoplasm. Employing a dielectrophoresis(DEP) based technique and a microfluidic system, the DEP response of many single CHO cells is measured and the spectrum...
Conference Paper
We present a microfluidic device for measuring the dielectrophoresis (DEP) response of single Chinese hamster ovary cells while in flow. The device measures the sign and amplitude of the DEP induced translation of single cells at two frequencies by sensing the change in impedance at microwave frequency as the cell passes over a multi-electrode tran...
Article
A universal, torque-mixing method for magnetic resonance spectroscopy is presented. In analogy to resonance detection by magnetic induction, the transverse component of a precessing dipole moment can be measured in sensitive broadband spectroscopy, here using a resonant mechanical torque sensor. Unlike induction, the torque amplitude allows equilib...
Conference Paper
Studying biological phenomena at the cellular level allows understanding the basics of cellular function and the mechanism of their interactions with internal or external stimuli. Among available single cell analysis techniques such as, fluorescent labeling, magnetic labeling, mechanical, and electrical approaches, electrical ones are of special in...
Conference Paper
Measuring carbon dioxide (CO 2 ) concentration plays an important role in environmental sciences, agri-food, medicine, packed food, and oil and chemical industry (R. Ali, T. Lang, S.M. Saleh, R.J. Meier and O.S. Wolfbeis, Analytical Chemistry, 83, 2846–2851, 2011). Spoilage of grain can be 3–10% in developed countries and as high as 30% in developi...
Conference Paper
Full-text available
We present a multi-frequency dielectrophoresis (DEP) based microfluidic device for characterizing the complex dielectric properties of single micron-sized particles while in flow. The device employs a multi-electrode transmission line sensor coupled to a microwave-interferometer, capable of subattofarad sensitivity, for detecting the DEP-induced tr...
Article
A microwave frequency reflectometer with atto-farad capacitance sensitivity has been designed and tested for detection of particles and cells in a microfluidic channel. The design is implemented on a printed circuit board. Capacitance sensitivity up to 1.25 aF is achieved in a 50 Hz bandwidth. The sensor was used for detection of 5.7 μm polystyrene...
Article
We present a near-field coupled passive sensor capable of measuring acidic and basic volatile concentration in its surrounding environment. The sensor employs an LC resonant circuit consisting of a spiral inductor connected in parallel with a voltage dependent capacitor (varactor). The volatile detector comprises a hydrogel coated pH-sensitive elec...
Article
One of the main uses of adenosine triphosphate (ATP) within mammalian cells is powering the Na +/K+ ATPase pumps used to maintain ion concentrations within the cell. Since ion concentrations determine the cytoplasm conductivity, ATP concentration is expected to play a key role in controlling the cytoplasm conductivity. The two major ATP production...
Conference Paper
In this work the dielectric response evaluated by dielectrophoresis (DEP) cytometer was used to track cytoplasm conductivity and therefore ion concentrations during apoptosis induced by inhibition of mitochondrial ATP production. Oligomycin was used to inhibit mitochondrial ATP production in Chinese hamster ovary (CHO) cells. During induction healt...
Conference Paper
Full-text available
It is important to detect corrosion at the initiation stage for effective intervention to minimize the impact of corrosion. In this paper, we present a passive inductively coupled coil sensor that can detect corrosion potential with respect to a reference electrode. The sensor has a sensitivity of 0.13 kHz/mV. Several experiment results of diffe...
Conference Paper
Electroporation affects the dielectric properties of cells by creating pores in their membrane which allow transport of ions. Dielectrophoresis (DEP) is a powerful technique to investigate electroporation of single biological cells. Here we study the frequency dependent response of Chinese hamster ovary (CHO) cells and investigate the effect of dif...
Conference Paper
Acidic and basic volatiles are a by-product of the food spoilage process. We demonstrate a near field coupled volatile absorption pH sensor that can be used for wireless food quality monitoring. The sensor is based on a LC resonator whose resonant frequency changes with the concentration of acidic and/or basic volatiles in the sensor's surrounding...
Article
A passive embeddable coupled coil sensor for remote bioprocess pH monitoring is described. The sensor is sterilizable, able to operate in a fluid medium, and small enough to fit inside a small bioreactor or test tube. It consists of a planar spiral inductor connected parallel to a varactor forming an LC resonant circuit. A pH combination electrode...
Conference Paper
We present a passive tag capable of detecting basic volatiles in the surrounding environment. The tag is based on a voltage dependant frequency shift approach using a LC resonator comprised of a spiral inductor in parallel with a varactor. The volatile detector, comprised of a pair of pH-sensitive electrodes coated with a very thin layer of hydroge...
Article
Full-text available
We present a printed circuit board-based wireless inductively coupled corrosion potential sensor for monitoring corrosion of steel-reinforced concrete civil infrastructure. The sensor is a passive LC coil resonator whose resonant frequency varies owing to the corrosion potential produced by two electrodes connected across a voltage-controlled capac...
Article
To ensure maximum productivity of recombinant proteins it is desirable to prolong cell viability during a mammalian cell bioprocess, and therefore important to carefully monitor cell density and viability. In this study, five different and independent methods of monitoring were applied to Chinese hamster ovary (CHO) cells grown in a batch culture i...
Article
Full-text available
In nanosecond pulsed electroporation of biological cells nanosecond duration pulses with high frequency spectral content are applied to the cell. We show that accurate modeling of the electroporation process on these time scales requires considering the effect of the dielectric dispersion on the electric potential across the membrane. We describe t...
Conference Paper
We present a semi-automated event identification method for collecting the dielectrophoretic signatures of cells flowing through a dieletrophoretic cytometer. The marker free dielectrophoresis (DEP) cytometer presented in this study is capable of detecting electronic signatures of cells which identifies Claussius-Mossotti factor (CMF). The CMF can...
Conference Paper
A microwave tomography system utilizing an inexpensive data acquisition system is introduced. The data acquisition system comprises several antennas surrounding an object-of-interest, field measuring probes distributed evenly in the measurement chamber, and a lock-in amplifier unit to perform measurements at audio frequencies based on the modulated...
Article
Corrosion of reinforcing steel, which results in premature deterioration of reinforced concrete structures, is a worldwide problem. Most corrosion sensing techniques require some type of wired connection between the sensor and monitoring electronics. This causes significant problems in their installation and long-term use. In this paper we describe...
Article
Full-text available
The importance of maximizing power transfer through overhead transmission lines necessitates the use of dynamic power control to keep transmission line temperatures within acceptable limits. Excessive conductor operating temperatures lead to an increased sag of the transmission line conductor and may reduce their expected life. In this paper, a pas...
Article
Full-text available
Temperature must be accounted for in order to provide accurate measurements in electrode-based pH sensors. We present an integrated wireless passive sensor for remote pH monitoring employing temperature compensation. The sensor is a resonant circuit consisting of a planar spiral inductor connected in parallel to a temperature-dependent resistor (th...
Conference Paper
We describe a microfluidic device integrated with a microwave interferometric sensor that is able to simultaneously electroporate and measure the dielectrophoresis (DEP) response of single biological cells. The system can measure changes in dielectric properties of a cell permeabilized using a high-intensity pulsed electric field (PEF) from a few s...
Conference Paper
In this work we demonstrate a printed circuit board based wireless inductively coupled corrosion potential sensor for monitoring steel reinforced concrete civil infrastructure. The sensor uses a coupled coil resonator whose resonant frequency varies due to the corrosion potential being applied across a varactor diode. The sensor is interrogated ext...
Conference Paper
Full-text available
In this work we demonstrate a printed circuit board based wireless inductively coupled corrosion potential sensor for monitoring steel reinforced concrete civil infrastructure. The sensor uses a coupled coil resonator whose resonant frequency varies due to the corrosion potential being applied across a varactor diode. The sensor is interrogated ext...
Conference Paper
We present a wireless pH sensor which utilizes water as an absorptive medium for gaseous organic acids. The potential of a pH-sensitive commercial mixed metal oxide (MMO) electrode with respect to a pH-insensitive Ag/AgCl electrode influences LC sensor resonant frequency via a varactor diode. The sensitivity of MMO electrode potential to electrolyt...
Conference Paper
A wireless passive pH sensor for continuous remote bioprocess monitoring is presented. The sensor is small enough to fit inside a small bioreactor or test tube. It consists of a planar spiral inductor connected in parallel to a varactor forming a LC resonant circuit. A pH combination electrode made of an iridium/iridium oxide sensing electrode and...
Conference Paper
We present a microfluidic device able to electroporate and measure the resultant changes in dielectric properties of single biological cells. The device can measure the dielectrophoresis (DEP) response of the electroporated cell from a few seconds after exposure to electroporating pulses. Studying electroporation at the single cell level can provid...
Conference Paper
We present a semi-automated event identification method for collecting the dielectrophoretic signatures of cells flowing through a dieletrophoretic cytometer. The marker free dielectrophoresis (DEP) cytometer presented in this study is capable of detecting electronic signatures of cells which identifies Claussius-Mossotti factor (CMF). The CMF can...
Article
Full-text available
The instrument described here is an all-electronic dielectrophoresis (DEP) cytometer sensitive to changes in polarizability of single cells. The important novel feature of this work is the differential electrode array that allows independent detection and actuation of single cells within a short section ( ∼ 300 μm) of the microfluidic channel. DEP...
Article
Asymptotic limits of Negative Group Delay (NGD) in linear causal media satisfying Kramers-Kronig relations are investigated. Even though there is no limit on the NGD-bandwidth product of a linear medium, it is shown that the out-of-band to center frequency amplitude ratio, or out-of-band gain, increases with the NGD-bandwidth product, and is propor...
Article
Electroporation affects the dielectric properties of cells by creating pores in their membrane which allow transport of ions in and out of cells. Dielectric characterization techniques are powerful tools to investigate the time evolution of electroporation induced changes. Here we employ a dielectrophoresis (DEP) technique to study the effect of el...
Article
A one-dimensional medium capable of bidirectional lossless negative group delay electromagnetic wave propagation is described. The medium is implemented as a microwave circuit comprising two symmetric resonator-loaded transmission lines, with active gain compensation and coupled through power combiners. We experimentally demonstrate the circuit is...
Article
A design procedure for filter-antenna modules in substrate integrated waveguide technology is presented. The filter antenna module is designed as a second order filter, with the output resonator loaded with the radiating element. The design procedure is developed in three stages, which are explained in detail through the design of two filter-antenn...
Article
This paper introduces a 2-dimensional conformal transformation scheme for the parameter extraction of an arbitrary overhead transmission line or underground cable in an unbounded lossy space. The quasi-magnetic Helmholtz equation is solved using the finite element method (FEM). A modified bilinear transformation is employed to transform the unbound...
Conference Paper
We present a wireless passive sensor for remote in vivo milk pH measurement. The sensor consists of a planar spiral inductor connected in parallel to a varactor forming a LC resonant circuit. A pH combination electrode made of an iridium/iridium oxide sensing electrode and a silver/silver chloride reference electrode, is connected in parallel to th...
Article
Full-text available
A microwave near field phase imaging technique has been achieved by an on-chip spintronic sensor. The sensor directly rectifies a microwave field into a dc voltage signal by employing the spintronic principle, in which the relative phase between microwave electric and magnetic fields plays an important role. By manipulating the relative phase, the...