Colin Dalton

University of Calgary, Electrical and Computer Engineering, Faculty Member

Followers

Following

Co-authors

Public Views

Biomedical engineer with high quality publications and a strong background in knowledge translation. Expert in advanced manufacturing technologies for biomedical micro-systems, with a range of teaching and supervisory experience. Over 10 years of collaborative interdisciplinary research advancing healthcare solutions. Excellent communication and leadership skills in cross-faculty team environments.

less

InterestsView All (6)

Uploads

Papers by Colin Dalton

Electromanipulation of micro and nano scale particles

Microfluidics Devices For Genetic Analysis Of Cancer

ABSTRACT

Electrorotation of Ascaris suum

We report electrorotation studies of ova of the nematode Ascaris suum. Electrorotation, the proce... more We report electrorotation studies of ova of the nematode Ascaris suum. Electrorotation, the process of inducing controlled cellular spin by using rotating electric fields, is sensitive to the dielectric properties of microbiological organisms (ARNOLD, W.M. & ZIMMERMAN, U., 1988: Journal of Electrostatics, 21, 151-191). Ascaris suum is the large roundworm infecting swine which can cross infect to humans (ANDERSON, T.J.C., 1995: Parasitology, 110 Pt2, 215-219). An adult female worm can lay in excess of 200,000 fertilised ova per day into the environment, which in temperate climates can remain viable for 7 years. There are currently some 59 million people at risk of some morbidity from Ascariasis (DeSILVA, N.R. et al., 1997: Tropical Medicine & International Health, 2-6, 519-528). We present distinct differences in the electrorotational response between fertilised and unfertilised ova of A. suum which can be used for identification purposes in mixed populations. We also report variatio...

Integrated Electrokinetic Microfluidic Systems for Cell Detection and Separation

Electrokinetic Particulate Laboratory-on-a-chip (Biofactory) Technology

Fertilization state of <I>Ascaris suum</I> determined by electrorotation

Journal of Helminthology, 2006

Electrorotation is a non-invasive technique that is capable of detecting changes in the morpholog... more Electrorotation is a non-invasive technique that is capable of detecting changes in the morphology and physicochemical properties of microorganisms. The first detailed electrorotation study of the egg (ovum) of a parasitic nematode, namely Ascaris suum is described to show that electrorotation can rapidly differentiate between fertilized and non-fertilized eggs. Support for this conclusion is by optical microscopy of egg morphology, and also from modelling of the electrorotational response. Modelling was used to determine differences in the dielectric properties of the unfertilized and fertilized eggs, and also to investigate specific differences in the spectra of fertilized eggs only, potentially reflecting embryogenesis. The potential of electrorotation as an investigative tool is shown, as undamaged eggs can be subjected to further non-destructive and destructive techniques, which could provide further insight into parasite biology and epidemiology.

Download

Mixture Theory approach to microneedle enhanced drug delivery into tissue

Electrical stimulation and enhanced axon regeneration: Novel in vivo and in vitro findings

Despite assumptions otherwise, axon regeneration after peripheral nerve injury is delayed and inc... more Despite assumptions otherwise, axon regeneration after peripheral nerve injury is delayed and incomplete. Brief low frequency electrical stimulation (ES) applied immediately after injury is known to improve axonal regeneration. We previously found that ES enhances axon-Schwann cell partnership and is associated with improved long term regeneration, including functional recovery. In this work we describe additional and novel features of the benefits of ES. Mice with a thy-1 YFP transgene and fluorescent peripheral axons were analyzed and divided into ES and sham (S) stimulation groups (n=5/group). Sciatic nerves in each group were transected and repaired within a silicone tube (2 mm gap). The ES paradigm, as identified previously in the Gordon laboratory (0.1ms, 3V, 20Hz for 1 h) was applied immediately thereafter. YFP axons were live imaged for 4 weeks and compound muscle action potentials (CMAPs) were Abstract Print View http://www.abstractsonline.com/Plan/AbstractPrintView.aspx?.....

Electrical Stimulation and Augmented Peripheral Nerve Regeneration in Diabetics: Potential Role of PI3-K Signaling Pathway

Rapid determination of parasite viability using AC electrokinetic techniques

A novel bio-mimicking, planar nano-edge microelectrode enables enhanced long-term neural recording

by Colin Dalton and Naweed Syed

Our inability to accurately monitor individual neurons and their synaptic activity precludes fund... more Our inability to accurately monitor individual neurons and their synaptic activity precludes fundamental understanding of brain function under normal and various pathological conditions. However, recent breakthroughs in micro-and nano-scale fabrication processes have advanced the development of neuro-electronic hybrid technology. Among such devices are three-dimensional and planar electrodes, offering the advantages of either high fidelity or longer-term recordings respectively. Here, we present the next generation of planar microelectrode arrays with " nano-edges " that enable long-term (≥1 month) and high fidelity recordings at a resolution 15 times higher than traditional planar electrodes. This novel technology enables better understanding of brain function and offers a tremendous opportunity towards the development of future bionic hybrids and drug discovery devices. Various neuronal activity recording and stimulating devices enable cellular exploration 1–3 using micro-and nano-devices 4. A multitude of penetrating and non-penetrating nanopillar electrodes 5–7 , carbon nanotube electrodes 8 , mushroom-shaped protruding microelectrodes 9 , planar microelectrode arrays (MEAs) etc. have been used to record neuronal activities. Among such devices are three-dimensional and planar microelectrodes, each with their respective advantages and disadvantages. Whereas, the three-dimensional electrodes tend to allow for high fidelity recordings they only do so over a short time period (hours to days). On the other hand, the planar microelectrodes permit longer-term recordings (weeks to months), albeit at the expense of low signal resolution. Ideally, combining both advantages would permit long-term and high-resolution recordings, which, in turn, could offer new opportunities to monitor and record subtle aspects of brain activity. Inspired by the structural attributes of a synaptic cleft, our team reports here on the next generation of planar microelectrode arrays with nano-edges offering high fidelity recordings over long time periods. Design and analysis Inspired by the morphology of a synaptic cleft, whereby both pre-and postsynaptic structures are juxtaposed and semi-encapsulated, we developed microelectrodes mimicking a synapse morphology as well as neuronal juxtapo-sition with their adjacent cells. Specifically, microelectrodes that " bio-mimic " the postsynaptic cleft were designed to exhibit 'nano-edges' that provide a tighter physical and dielectrical seal between the device and the neuron. This structural geometry was also anticipated to prevent the leakage of current into the surrounding extracellular milieu, thus preserving and augmenting the functional integrity of chemical and electrical neuronal signal processing (Fig. 1a,b). We named these types of microelectrodes as " nano-edge microelectrodes ". Gold planar microelectrodes were fabricated using a standard photolithography technique and lift-off process. Electrode sizes, and distances between them, were adjusted according to our experimental needs by modifying the photomask designs, allowing us to keep the design relatively simple, economical and scalable. Once the planar microelectrodes were fabricated, the nano-edge was added using a custom photolithography process. Following the fabrication, we characterized and validated the morphological attributes of the microelectrodes with atomic force microscopy (Fig. 1c) and were able to qualitatively confirm the presence of the nano-edges (Fig. 1d).

Download

Development of a planar microelectrode array offering long-term, high-resolution neuronal recordings

by Colin Dalton and Naweed Syed

All nervous system functions, ranging from simple reflexes to learning and memory, rely on networ... more All nervous system functions, ranging from simple reflexes to learning and memory, rely on networks of interconnected brain cells called neurons, which initiate and convey electrical information. Monitoring neuronal activities of a large neuronal ensemble, non-invasively and over an extended time period, is pivotal for understanding all brain functions. A variety of neuro-electronic interfaces now allow monitoring of neuronal and ion channel activities. These neuronal monitoring devices are however limited vis-à-vis their efficacy, fidelity and longer-term recording capabilities. Here we report on a novel microelectrode array technology that allows for the detection and characterization of neural activity from individual cells and networks, over long periods of time and with a higher signal-to-noise ratio than commercially available devices. Our in-house development of planar microelectrode arrays has focused on modifying design parameters and fabrication techniques to improve their performance. One such device, the Soma-Soma Chip (SS-Chip), allows us to record activity from single and paired cells (pre-and post-synaptic neurons) continuously over extended periods of time with a signal-to-noise ratio higher than similar standard devices. This allows for the analysis of neural activity, which can help to characterize firing patterns of neurons at various developmental-stages. Of particular importance is the precise " signatures " of neuronal firing pattern that offers a unique opportunity to decipher how neuronal activity influences brain network connectivity. Our data also underscore the importance of further development of novel microelectrode array technologies. These developments will provide novel tools and open new research opportunities critical for understanding the fundamental cellular and network properties underlying network activity under both normal and disease conditions.

Download

Accelerating Neurite Outgrowth Through Electric Field Manipulation

by Michael Purdy and Colin Dalton

Brief electrical stimulation accelerates neuronal regeneration both in individual cells and in li... more Brief electrical stimulation accelerates neuronal regeneration both in individual cells and in living models. In vitro experiments facilitate further understanding of regenera-tion mechanisms, and are typically carried out by plating individual cells on slides or microelectrode arrays. However, uniform electric fields may be better suited to enhance growth than traditionally used point-source fields. Applied uniform electric fields would allow for long distance stimulation without requiring destructively high voltages, and may be more easily transferred to an implantable design for clinical use. The viability of uniform electric field stimulation was explored in this study through the use of a custom-fabricated planar mi-croelectrode array. Simulation of several electrode configurations resulted in the design of a parallel plate anode-cathode pair. Several such electrode pairs were embedded onto a single microelectrode array at various gap widths, to allow for the study of electric field strength on overall growth. With this novel electrode array, individual Lymnaea snail cells were stimulated with a 20 Hz, 1 volt pulse train for one hour. The impact of this stimulation on growth was measured 24 hours later, and compared to control cells plated on identical electrode arrays that were not stimulated. Stimulated cells showed an increase in overall neurite length compared to the control group. This effect was seen regardless of stimulus magnitude, within the range of 1000 – 2000 mV/mm.

Download

A novel alternating current multiple array electrothermal micropump for lab-on-a-chip applications

The AC electrothermal technique is very promising for biofluid micropumping, due to its ability t... more The AC electrothermal technique is very promising for biofluid micropumping, due to its ability to pump high conductivity fluids. However, compared to electroosmotic micropumps, a lack of high fluid flow is a disadvantage. In this paper, a novel AC multiple array electrothermal (MAET) micropump, utilizing multiple microelectrode arrays placed on the side-walls of the fluidic channel of the micropump, is introduced. Asymmetric coplanar microelectrodes are placed on all sides of the microfluidic channel, and are actuated in different phases: one, two opposing, two adjacent, three, or all sides at the same time. Micropumps with dif- ferent combinations of side electrodes and cross sections are numerically investi- gated in this paper. The effect of the governing parameters with respect to thermal, fluidic, and electrical properties are studied and discussed. To verify the simula- tions, the AC MAET concept was then fabricated and experimentally tested. The resulted fluid flow achieved by the experiments showed good agreement with the corresponding simulations. The number of side electrode arrays and the actuation patterns were also found to greatly influence the micropump performance. This study shows that the new multiple array electrothermal micropump design can be used in a wide range of applications such as drug delivery and lab-on-a-chip, where high flow rate and high precision micropumping devices for high conductivity flu- ids are needed

Download

HIGH EFFICIENT BIOFLUID MICROMIXING USING ULTRA-FAST AC ELECTROTHERMAL FLOW

Electrokinetics have been widely used in lab-on-a-chip devices for fluid manipulation application... more Electrokinetics have been widely used in lab-on-a-chip devices for fluid manipulation applications. The AC electrothermal (ACET) effect is a highly efficient technique for biofluids (σ>0.1 S/m) active micromixing, which can be used in chemical, biological, and medical analysis systems. In this paper, a novel idea of employing microelectrode arrays placed on side-walls of a fluidic microchannel for increasing the mixing efficiency of biofluids is numerically investigated. It was reporte d that coplanar asymmetric microelectrode arrays are capable of creating ACET vortices in the bulk of a high conductive electrolyte solution. Two electrode arrays can be placed on the sidewalls of a microchannel, each of which has a different role, one pumps the biofluid while the other mixes it. Two different actuation patterns were applied to the electrodes. One pair of microelectrodes was simulated and the simulation procedure was then verified by conducting experiments for ACET flow measurement in a similar geometry. Microelectrode arrays were fabricated on 1mm thick glass substrates using photolithography. A 800 µm thick fluidic microchannel was fabricated by soft lithography of Polydimethylsiloxane (PDMS). The results showed that such a technique can dramatically increase the mixing of the solution while pumping is taking place. The mechanism was capable of efficiently mixing biofluid solutions (resultant concentration ratio of up to 80%) in a short time (<3 min) and short distance (<600 µm) for a 300×300 µm2 fluidic microchannel cross section area. Medical analysis such as heterogeneous immunoassays can be potential applications of such micromixing technique.

Download

A NOVEL AC ELECTROTHERMAL MICROPUMP FOR BIOFLUID TRANSPORT USING CIRCULAR INTERDIGITATED MICROELECTRODE ARRAY

Electrokinetic micropumps have been widely used in lab-on-a-chip devices. The AC electrothermal (... more Electrokinetic micropumps have been widely used in lab-on-a-chip devices. The AC electrothermal (ACET) effect is highly efficient for biofluidic micropumping, but is unable to generate high flow rates. Attempts to increase ACET flows, such as applying a wide range of actuation voltages, using asymmetric microelectrode arrays and using 3D microelectrodes have been reported. In this paper a novel idea of employing circular coplanar asymmetric microelectrodes placed on the perimeter of a microchannel is explored. An array of microelectrodes is simulated using COMSOL Multiphysics software. The micropump output shows relatively high flow rates compared to other ACET micropumps which have the same electrode dimensions. Moreover, the idea of using different micropumps with scaled dimensions is investigated. The results show that a highly efficient ACET micropump can be achieved if an appropriate electrode size-to-channel dimension ratio is selected. The results also show that a micropump with a scale of 0.2 can show negligible flow rate, but if the electrodes are used in a micropump with the scale of 1, a flow rate of 15 ×10 6 µm 3 /s can be generated. This new ACET pump design can be utilized for lab-on-a-chip applications, specifically in biofluid delivery systems.

Download

VIBRATION EFFECT ON CROSS-FLOW AND CO-FLOW FOCUSING MECHANISM FOR DROPLET GENERATION

Microbubbles are widely used in many industries such as water treatment, drug coating, and ultras... more Microbubbles are widely used in many industries such as water treatment, drug coating, and ultrasonic contrast agents. Cross-flow focusing and co-flow focusing are considered basic mechanisms used for microbubble generation. Typically, to achieve micron-sized droplets requires structure dimensions in the same order of magnitude of the desired droplet sizes. In this paper we report a method of applying an external vibration to a cross-flow and co-flow focusing structure, which allows for smaller droplets to be generated. The junction dimension was 700×400 µm, and the channel width was 800 µm. The two assumed fluids are selected in a way that the Capillary number is high (Ca>10) to make use of necking effect occurred in the downstream. Linear vibration was exerted on the microchannel structure in the direction of central flow. A 2D structure was simulated using finite element software, and the numerical approach was then verified by comparing the experimental data of a typical cross-flow focusing structure taken from our previous study with the corresponding simulation assuming the same parameters. The results show that although the droplet generation regime depends on flow ratio (Qa/Qw) and vibration parameter (ampl×freq), Capillary number also has a significant effect on the regime. Briefly, applying a low-cost linear vibration to the conventional flow focusing structures can be used as an accurate controlling technique for increasing the chance of droplet generation. In fact, vibration motion can change the flow regime and breakup mechanism. It can also change the breakup point at which the droplets are formed.

Download

FLUID FLOW STUDY OF AN AC ELECTROTHERMAL MICROPUMP CONSISTING OF MULTIPLE ARRAYS OF MICROELECTRODES FOR BIOFLUID APPLICATIONS

Electrokinetics has many applications in a wide range of areas, such as lab-on-a-chip and biomedi... more Electrokinetics has many applications in a wide range of areas, such as lab-on-a-chip and biomedical microdevices. The electrothermal effect has been used for biofluid delivery systems since it has high pumping efficiency for high conductive liquids (>0.1 S/m) compared to other electrokinetic techniques such as electroosmosis. AC electrothermal (ACET) micropumps are based on the temperature gradient caused by Joule heating or an external heat source, which generates permittivity and conductivity gradients in the bulk of the liquid. When the liquid is subjected to an electric field, the ACET force is created. Electrode geometry significantly affects the electric field distribution, which can yield stronger ACET forces. Previously electrode dimension optimization has been performed for a single-array coplanar asymmetric configuration in order to obtain maximum ACET velocities. In this paper we expand the study to other governing parameters in a multiple-row microelectrode array configuration consisting of microelectrodes placed on top, bottom , and/or side walls of a microchannel. The studied parameters are the substrate material and thickness , ambient temperature, fluid viscosity, and actuation frequency. Electrode dimensions remain constant during the study (120 µm wide and 20 µm thin electrodes, 20 µm gap). The study is performed using finite element analysis software for one pair of microelectrodes on each array with periodic boundary conditions. The simulation data is then compared with experimental data for a single combination of the aforementioned parameters. The results show that the effect of these parameters on ACET flow can be significant.

Download

Peripheral neuron plasticity is enhanced by brief electrical stimulation and overrides attenuated regrowth in experimental diabetes

Peripheral nerve regrowth is less robust than commonly assumed, particularly when it accompanies ... more Peripheral nerve regrowth is less robust than commonly assumed, particularly when it accompanies common clinical scenarios such as diabetes mellitus. Brief extracellular electrical stimulation (ES) facilitates the regeneration of peripheral nerves in part through early activation of the conditioning injury response and BDNF. Here, we explored intrinsic neuronal responses to ES to identify whether ES might impact experimental diabetes, where regeneration is attenuated. ES altered several regeneration related molecules including rises in tubulin, Shh (Sonic hedgehog) and GAP43 mRNAs. ES was associated with rises in neuronal intracellular calcium but its strict linkage to regrowth was not confirmed. In contrast, we identified PI3K–PTEN involvement, an association previously linked to diabetic regenerative impairment. Following ES there were declines in PTEN protein and mRNA both in vitro and in vivo and a PI3K inhibitor blocked its action. In vitro, isolated diabetic neurons were capable of mounting robust responsiveness to ES. In vivo, ES improved electrophysiological and behavioral indices of nerve regrowth in a chronic diabetic model of mice with pre-existing neuropathy. Regrowth of myelinated axons and reinnervation of the epidermis were greater following ES than sham stimulation. Taken together, these findings identify a role for ES in supporting regeneration during the challenges of diabetes mellitus.

Download

Effect of planar microelectrode geometry on neuron stimulation: Finite element modeling and experimental validation of the efficient electrode shape

by Colin Dalton and Naweed Syed

• Stimulation efficiency of circular, spiral, and star perimeter electrodes with the same area wa... more • Stimulation efficiency of circular, spiral, and star perimeter electrodes with the same area was compared at the cellular level. • Circular microelectrode requires less stimulus to activate a cell compared to the spiral and star perimeter shaped electrodes. • The average current density and not the maximum current density of the electrode that determines its stimulation efficiency at the cellular level. • Star electrodes with larger perimeter than circular electrodes did not result in higher neural stimulation efficiency at the cellular level. a b s t r a c t Background: Microelectrode arrays have been used successfully for neuronal stimulation both in vivo and in vitro. However, in most instances currents required to activate the neurons have been in un-physiological ranges resulting in neuronal damage and cell death. There is a need to develop electrodes which require less stimulation current for neuronal activation with physiologically relevant efficacy and frequencies. New method: The objective of the present study was to examine and compare the stimulation efficiency of different electrode geometries at the resolution of a single neuron. We hypothesized that increasing the electrode perimeter will increase the maximum current density at the edges and enhance stimulation efficiency. To test this postulate, the neuronal stimulation efficacy of common circular electrodes (smallest perimeter) was compared with star (medium perimeter), and spiral (largest perimeter with internal boundaries) electrodes. We explored and compared using both a finite element model and in vitro stimulation of neurons isolated from Lymnaea central ganglia. Results: Interestingly, both the computational model and the live neuronal stimulation experiments demonstrated that the common circular microelectrode requires less stimulus to activate a cell compared to the other two electrode shapes with the same surface area. Our data further revealed that circular electrodes exhibit the largest sealing resistance, stimulus transfer, and average current density among the three types of electrodes tested. Comparison with existing methods: Average current density and not the maximum current density at the edges plays an important role in determining the electrode stimulation efficiency. Conclusion: Circular shaped electrodes are more efficient in inducing a change in neuronal membrane potential.

Download

Colin Dalton

Uploads

Papers by Colin Dalton

Log In