Douglas J Thomson

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

The ability to quantitatively and non-invasively characterize complex multiphase geomaterials is still a major challenge to the engineering, construction, and geophysical fields. In the context of accelerating climate change, construction on permafrost requires remedial measures and an appropriate characterization of permafrost (e.g., ice content,...

Faults in a grounding network pose a serious threat to power system equipment protection and worker safety. A large number of vertical electrodes are used in a grounding network and break-points in these due to soil induced corrosion is one of the prime reasons for faults. We present a rod insertion time domain reflectometry (TDR) technique for ver...

Soil scour near a bridge pier foundation is one of the leading causes of bridge failures. Traditional vibration-based scour monitoring methods are nearly incapable of quantifying scour levels using a single acceleration response without knowledge of excitation information. In this paper, a new output-only scour level prediction method is introduced...

Reducing greenhouse gas emissions including carbon dioxide (CO2) is central to minimizing the human contribution to global warming. Industrial activities and transportation are some of the main contributors to carbon dioxide emission. Bridges are the key element in the transportation system and many of them are reaching the end of their designed se...

Fibre reinforced polymer (FRP) rods are widely used as corrosion-resistant reinforcing in civil structures. However, developing a method to determine the loads on in-service FRP rods remains a challenge. In this study, the entropy of acoustic emission (AE) emanating from FRP rods is used to estimate the applied loads. As loads increased, the fracti...

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...

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...

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...

Composite action between steel girders and concrete slab is an important mechanical feature that needs to be maintained so that bridges can carry the applied load safely. This mechanical feature is maintained through the shear studs installed at the top flange of the steel girders. These shear studs keep the steel girders and the concrete slab work...

Composite action between steel girders and concrete deck slabs is an important feature of slab-on-girder bridges. The composite action between steel girders and concrete slabs is maintained through the shear studs installed at the top surface of the top flange of the steel girders. These shear studs keep the steel girders and the concrete deck slab...

Bridges are key elements of the transportation system. The load carrying capacity of a bridge can be evaluated through load testing. However, this only provides a snap shot of the structure at a particular time. In this work, sensors, including strain gauges, accelerometers, and thermocouples, are used to collect real time structural responses to t...

It is critical to detect cracks in steel girders of bridges before they have the potential to compromise the integrity of the structure. Both distributed binary sensors and distributed fiber optic sensors are capable of detecting cracks that are wider than 0.2 mm in steel girders. The objective of this paper is to report the optimum placement of th...

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...

Determining the integrity of grounding electrodes is challenging and there is need to augment expensive and time consuming excavation based methods. In this work pulse-echo methods based on acoustic guided waves were tested on model ground rods with machined model corrosion pits. The generation and propagation of the guided acoustic waves in the mo...

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...

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...

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...

Steel girder bridges make up a significant percentage of all bridges. Many of the steel girder bridges are aging and approaching their designed service lives. Crack formation and its propagation over time is one of the main deficiencies of aging steel girders and may result in unusable or unsafe service conditions. The existing distributed crack de...

Axle detection is a critical monitoring process that needs to be implemented on bridges so that the number of axles of crossing vehicles can be determined. Most bridge design codes specify bridge design loads based on certain trucks configurations. Reviewing and updating bridge design codes depend on an accurate measurement of the nature of the loa...

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...

Steel girder bridges make up a significant percentage of all bridges. Many of the steel girder bridges are aging and approaching their designed service lives. Crack formation and its propagation over time is one of the main deficiencies of aging steel girders and may result in unusable or unsafe service conditions. The existing distributed crack de...

Acoustic emission (AE) signal has proved to be a useful tool for monitoring structures reinforced with FRP composites such as Fiber Reinforced Polymer (FRP) reinforced beams, carbon FRP (CFRP) sheets, or steel fiber reinforced concrete. This work focuses on studying the behavior of pultruded FRP bars, which have been manufactured using continuous f...

It is well documented that civil infrastructure, including steel bridges, are aging and are approaching the end of their design service life. One of the challenging problems with aging steel girder bridges is the potential for crack formation and propagation that may result in unusable service conditions. Timely detection of cracks demands frequent...

Fiber reinforced polymer (FRP) rods are used for pre-stressing and reinforcing in civil engineering applications. Damage in FRP rods can lead to sudden brittle failure, therefore, a reliable method that provides indicators of damage progression and potential failure in FRP rods is highly desirable. Acoustic emission (AE) signal analysis has been us...

North American infrastructure, including steel bridges, are aging and reaching the end of their service lives. Over time, environmental stresses and cyclic truck traffic over bridges may lead to crack formation and crack propagation in the steel girders used in bridges. Cracks in steel girders decreases the load bearing capacity of the superstructu...

An integrated dielectrophoresis cytometer has been designed and implemented using a standard 0.35 μm CMOS technology. This design makes use of differential ring oscillators. The frequency difference between the two oscillators, in presence of a cell, is detected by an XOR gate. The frequency difference is then measured by a frequency counter. This...

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...

A simple high frequency capacitance sensor with 180 aF sensitivity is designed for a wide range of microfluidic applications. The sensor is implemented utilizing differential ring oscillators operating at <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">~</sub> 240 MHz with a differential signal at <sub...

Differential 3-stage and 5-stage, ring oscillator based capacitance sensors were designed and integrated using 0.35 μm CMOS technology. The sensor operates at 0.7 GHz and 1.4 GHz and achieves ∼14 aF capacitive sensitivity. The use of CMOS technology makes the integration of the sensing circuit, and the detection microelectrodes on chip possible. A...

A passive wireless sensor for the measurement of ac electric fields emanating from high-voltage (HV) apparatus using radio-frequency (RF) resonant cavities is presented. The sensor is composed of a coaxial transmission line resonator, where the resonant frequency is perturbed by capacitively coupled varactors. HV apparatus induces a bias voltage on...

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...

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...

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...

Structural health monitoring systems are required to detect the presence of cracks on structures. Currently available sensing systems are costly and difficult to install. In this work, a new crack sensing system based on the propagation of cracks from the structure through a bonded conductor is presented. The conductor is severed when a crack on th...

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...

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...

In this paper, a wireless interrogation method based on pulse-echo technique is demonstrated for passive resonator based sensors. This technique can be employed for the measurement of time varying measurands. The measurand studied in this paper is a 60 Hz AC electric potential that varies the resonance frequency of a passive, resonator sensor. The...

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...

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...

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...

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...

Capacitance sensors with a capacitive sensing electronics have been calibrated for measuring moisture content (MC) in masonry stones. A total of 64 samples were tested. The MCs determined by gravimetry are correlated to the signals measured by the capacitive sensing electronics. The relationship between the MC and the measured voltage has been mode...

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...

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...

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...

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...

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...

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...

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...

Acoustic emission (AE) activity occurring during tests on fibre reinforced polymer (FRP) materials has proven to be indicative of the state of damage in a sample. In this experimental program, FRP tendons were instrumented with AE monitoring equipment and tested in tension in order to develop a simple AE-based damage monitoring system. Using contro...

The economic case for extending the service life of structures using the combination of testing and structural health monitoring (SHM) is very strong. In the USA, it is estimated that there are 70,000 structurally deficient bridges. Surprisingly, 12,000 have no deficiency other than a low load rating, with only six reported to have a rating based o...

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...

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...

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...

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...

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...