Progress 01/01/18 to 12/31/18
Outputs
Target Audience:Research students, post-doctoral researchers, faculty and scientists who attend scientific conferences including the Electrochemical Society, International Meeting on Chemical Sensors, Association of Microbiologists, and Biomedical Engineering Society. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Graduate student training and completion of PhD studies. How have the results been disseminated to communities of interest?Results have been published in book chapter, journal papers, conference papers and a dissertation. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Capture of Salmonella bacteria on magnetically actuated cillia was achieved and is reported in the publications in ECS Transactions, and also Disseration by S. Hanasoge.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
S. K. G. Hanasoge, P. J. Hesketh, A. Alexeev, ⿿Metachronal motion of artificial magnetic cilia, Soft Matter Vol. 14, pp. 3689-3693 (2018).
- Type:
Book Chapters
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, P. J. Hesketh, A. Alexeev, ⿿Magnetic thin film cilia for microfluidic applications, in Atlas of Cilia Bioengineering and Biocomputing, Editors: Richard Mayne, and Jaap den Toonder, River Publishers (2018) ISBN: 9788770220026
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
S. K. G. Hanasoge, A. Alexeev, P. J. Hesketh, , ⿿Microfluidic pumping using artificial magnetic cilia, J. Microsystems and NanoEngineering Vo. 4, No. 1, pg. 11, (2018).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, A. Alexeev, M. Erickson P. J. Hesketh, Y. R. Ortega, ⿿Artificial Cilia for Microfluidics Particle Capture, Transactions of the ECS Vol. 86, No. 16 pg 3-12 (2018).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, A. Alexeev, P. J. Hesekth, M. Erickson, J. Xu, Magnetic Beads and Artificial Cilia for Efficient Pre-concentration of Salmonella Bacteria, American Microbiology Meeting, Atlanta GA, April, 2018.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, A. Alexeev, M. Erickson, J. Xu, P. J. Hesketh, ⿿Magnetic Actuated Beating Cilia for Preconcentration of Bacteria, Spring ECS Meeting, Seattle, May 2018
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, A. Alexeev, M. Erickson, J. Xu, P. J. Hesketh, ⿿Artificial cilia for microfluidics particle capture, Fall ECS Meeting, Cancun, October 2018
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, A. Alexeev, M. Erickson, J. Xu, P. J. Hesketh, ⿿Bacteria Capture Using Artificial Magnetic Cilia, IMCS, Vienna Austria, July 2018.
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2019
Citation:
S. Hanasoge "Magnetic artificial cillia for microfluidic applications" PhD Dissertation in Mechanical Engineering, Georgia Institute of Technology, 2018.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
S. Hanasoge, A. Alexeev, P. Hesketh, "Designing magnetic cilia that exhibit metachronal motion," Abstract 2928, Biomedical Engineering Society Annual Meeting, Atlanta, GA, 17 ⿿ 20th October 2018
|
Progress 01/01/17 to 12/31/17
Outputs
Target Audience:Scientists and engineers working on food safety technology and students who attend meetings of the Electrochemical Society, the American Physical Society, and the uTAS meeting largest meeting on bioanalytical systems. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Training of graduate students in field of microfluidics and biosensing for application in food safety. How have the results been disseminated to communities of interest?Journal publications and presentations given at conferences and international scientific meetings What do you plan to do during the next reporting period to accomplish the goals?Test the sampling system with fluorescently labelled Salmonella in collaboration with Ynes Ortega at the Center for Food Safety at the University of Georgia. Quantify the capture with different spiked levels of bacteria in the sample. Examing the effects of using cantilever of different dimensions on the capture efficiency and the sample volumne throughput. Compile information collected to write journal publications and prepare conference papers on the results to disseminate our findings.
Impacts
What was accomplished under these goals?
We have developed and demonstrated microfluidic platform for capturing Salmonella bacteria using magnetic microbeads. We have also validated our results using lattice Boltzmann computer simulations. This system primarily mixes fluid in a microchannel by revolving magnetic microbeads around soft magnetic posts. The revolving beads enhance the fluid mixing, which in turns increases the chance of particles coming in contact with the beads. We have shown the capture of streptavidin coated beads that are revolving to capture biotin coated particles. Such capture can be extend to the capture of bacteria by using magnetic beads coated with bacteria specific antibody. The primary disadvantage of using such a microbeads based system is the low throughput. The beads can only capture particles in a channel of maximum depth. This limitation, however, can be overcome by using longer microstructures that extend into the microfluidic channel. Therefore, we propose the use of magnetic artificial cilia, which are hair like structures that can be manipulated using a magnetic field. Moving these hair like structures in a microfluidic channel can enhance the fluid mixing and thus enhance the chance of particle capture. These flexible structures can extend up to several hundred micrometers into the fluid. We have developed a fabrication process for making the artificial using simple microfabrication tools. The kinematics of beating a single isolated cilium is studied, and we have shown the spatially asymmetric motion under the influence of a simple rotating magnetic field. Such spatially asymmetric motion is essential of creating any microfluidic transport, because of negligible inertial effects. We understand the kinematic of motion of cilia in terms of governing non-dimensional sperm and magnetic numbers. We demonstrate that these numbers determine the operation of the cilia. Numerical simulations using COMSOL and lattice Boltzmann, both confirm our understanding of the cilia kinematics. We demonstrate the pumping capabilities of magnetic cilia and quantify the net pumping by an array of cilia. Our experimental setup, consisting of a microchannel loop, allows for direct visualization of flows created by the ciliary array. We vary various parameters such as direction and frequency of field, number of rows of cilia, channel height, spacing between the rows of cilia and establish the dependence of pumping on these parameters. We report high flow rates of up to , which translates to volumetric flowrate. The pressure drop created by this ciliary array is estimated to . Such systems can potentially be useful in applications which require low pressure drop and high flow rate, in low Reynolds number environments. Most natural occurring cilia are known to beat is a metachronal fashion, like a 'Mexican wave'. Such metachronal motion in the beating cilia are known to enhance fluid transport and particle capture properties. We demonstrate a simple mechanism for sequential one by one actuation of artificial cilia, which leads to metachronal motion similar to ones found in nature. We use cilia of varying lengths that are actuated by a uniform magnetic field to show this. We show the effects of changing length on cilium kinematics and the induced phase difference in the motion. We make use of this phase difference in their motion to actuate an array of cilia of increasing lengths in a metachronal fashion. Finally, we demonstrate bacteria capture on the surface of cilia by immobilizing anti-Salmonella antibody on the cilia surface. The immobilization is done in two steps. The first is the immobilization of streptavidin coated magnetic beads on the surface of the cilia. The second step is the immobilization of biotin-tagged antibody on the streptavidin beads. Following this process will leave microbeads that are coated with the antibody attached to the cilia surface. Next samples containing bacteria at various concentrations were introduced into a microchannel consisting of cilia at the bottom wall. These hair like protrusions from the surface of the channel, that oscillate, enhance the chances of bacteria capture. The results from these experiments suggest that the bacteria are selectively captured on the cilia surface. A microscopic visualization revels the higher concentration of bacteria on the cilia surface. These, preliminary experiments provide positive results, there is a need for better design and implementation. We have seen capture with bacteria concentration of cells per ml. The next step is to reduce the concentration and design a system that is capable of capturing lower concentrations of bacteria. Given the number of experimental variables, finding the optimum condition of maximum capture is critical. With the cilia based capture system, we are able to process of sample in .
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2018
Citation:
Srinivas Hanasoge, Peter J. Hesketh, Alexander Alexeev, "Microfluidic pumping using artificial magnetic cilia" Nature Microsystems and Nanoengineering
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Srinivas Hanasoge, Matthew Ballard, Peter J. Hesketh, Alexander Alexeev, "Asymmetric motion of magnetically actuated artificial cilia" uTAS Volume 17, pp. 3138-3145
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Srinivas Hanasoge, Matthew Ballard, Peter Hesketh, Alexander Alexeev, Magnetic thin films for active fluid manipulation in microfluidics Proceedings of uTAS 2017, Savanah, GA, October 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
P. J. Hesketh, Magnetically actuated synthetic cilia for microfluidics, INVITED TALK, AVS Meeting, Tampa, FL, October 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
S. Hanasoge, M. Ballard, A. Alexeev, P. J. Hesketh, Magnetic Cilia for Microfluidic Applications, Fall ECS Meeting, National Harbor, MA, November 2017.
|
Progress 01/01/16 to 12/31/16
Outputs
Target Audience:We have presented papers and posters at a number of scientific meetings including uTAS, SPIE,and the Electrochemical Society. The target audience is other scientists and researchers involved in developing micro-technology for biosensing and assay development. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Education of graduate students and involvement of undergraduate students in reserach project. How have the results been disseminated to communities of interest?We have presented papers and posters at a number of scientific meetings including uTAS, SPIE,and the Electrochemical Society. There was a lot of interest at the uTAS meeting about the use of cilia for fluid circulation in microchannels. At the SPIE and ECS meetings interest wasin using the sample preconcentration methods for target capture. What do you plan to do during the next reporting period to accomplish the goals?We will apply active cilia to quantify capture efficiency with cilia functionalized with antibody directed to the target Salmonella. We will quantify capture efficiency with active cilia, when functionalized antibody is attached to magnetic beads present in the flow, actively mixed by the cilia..
Impacts
What was accomplished under these goals?
A novel microsystem utilizing an array of rotating magnetic beads inside a microfluidic channel has been developed for mixing and capture at low Reynolds numbers. The magnetic beads are actuated via an external rotating magnetic field dynamically magnetizing small (<10 μm) soft magnetic features. The effectiveness of this system is experimentally evaluated in two separate common microfluidic operations, microfluidic mixing and particle capture or isolation. The hypothesis of the work is that the actuation of the magnetic beads will rapidly mix the system and the rapid mixing will increase the chance that a functionalized target particle will come into contact with the magnetic bead. The target could then be trapped via a protein-protein bond with the functionalization on the magnetic bead. The first operation, microfluidic mixing, is the ability for these beads to mix fluids inside a microfluidic channel. This was done by measuring the mixing of two streams of fluid as they flow over the rotating array of beads. This method demonstrated significant mixing (65%) in less than 300 μm of channel length if the magnetic beads are actuated at a high enough velocity relative to the bulk flow velocity. The second operation is the capacity to capture particles from the microfluidic channel. This capturing was accomplished via protein-protein bond between the surface functionalizations of the magnetic bead and the particle. This device demonstrated the capacity to capture >80% of particles that pass through the 400 μm array. This result was demonstrated in channels where the magnetic beads occupied less than 25% of the channel height. We have used numerical simulations to find that Salmonella can be captured using our device over a very short distance, and found that capture is most efficient when there is not a large spacing between soft magnetic discs, around which the superparamagnetic beads orbit. During this past year, we experimentally verified rapid capture of particles from a fluid sample. In our experiments, we demonstrated capture of up to 90% of the particles that were passed through a 390μm section of the microchannel, which contained an array of NiFe discs each orbited by two superparamagnetic beads. As we have seen in prior numerical studies, we found experimentally that the capture efficiency of our system generally decreases as the ratio of the flow velocity to the bead linear velocity increases. This is in large part due to the decreased residence time of the particles in the channel, but can also be attributed to the changing flow patterns in the channel as the ratio of velocities changes. In order to analyze a large amount of fluid in a short amount of time, a large throughput is desired for our device. One way to increase the throughput is to increase the height of the channel, which increases its cross-sectional area. However, increasing the channel height reduces the ability of the device to efficiently capture. In order to understand the effect of channel height on particle capture performance, we collected capture data in both experiments and numerical simulations in a 390μm capture section. We tested channel heights of 2a, 3a and 4a, where a is the microbead diameter. For all cases, we found efficient capture at low flow velocity ratios, with capture efficiency decreasing with increasing velocity ratio. However, the amount of decrease in capture efficiency with increasing velocity ratio is strongly dependent on the channel height. This not only confirms that the capture efficiency generally decreases with increasing channel height, but also shows us that this effect is relatively low in low velocity ratio flow conditions, while it is more pronounced at higher velocity ratios. Therefore we have studied magnetic cilia which can extend 250 - 400 micrometer across the channel to handle larger fluid volumes. Most eukaryotic organisms manipulate fluid by using cilia, which are hair like features that oscillate to produce net fluid motion. Biological cilia achieve this, even at the limit of low Reynolds number, through the use of complex asymmetric beating patterns which include an effective stroke and a recovery stroke in their beat cycles. There is little experimental evidence of the pumping effects of cilia. We have experimentally demonstrate magnetic micro-cilia based fluid manipulation techniques. Fluid manipulation is primarily determined by the bending pattern of the cilia in the forward and recovery strokes. The bending pattern and deflection of cilia can be defined by the sperm number,shows the ratio of viscous to elastic forces on the oscillating cilia, and defines the bending pattern of the cilia. The shape of the cilia and therefore the pumping depends on this number critically. We have shown an optimum in the sperm number for various functions of the cilia. We experimentally show the pumping due asymmetry in the forward and recovery strokes. This we do by directly imaging the cilia from the side view which clearly reveals the shape. The asymmetry in the power and recovery strokes is achieved in our experiments by varying their time. A difference in these times for the two strokes changes the shape and trajectory. This asymmetry allows for the manipulation of the fluid around it. We measure pumping speeds of up to 400 microns/s produced by arrays of these cilia. To order to simulate the fluid and solid dynamics of synthetic cilia, we used a computational method for fluid-structure interactions (FSI) that makes use of the LBM fully coupled through appropriate boundary conditions to a LSM, which models elastic solids as a system of distributed mass points (nodes) connected by harmonic springs arranged on a regular lattice. We modelled two different types of synthetic cilia. The first was an array of high aspect ratio flexible cilia with square cross-section. This model was used to demonstrate the basic physics of cilia oscillations. The second was a model uses ribbon-shaped cilia that closely replicate our experimental device, so as to facilitate an understanding of its dynamics. In both models, magnetic cilia actuation was simulated through the application of sinusoidal oscillating forces to the solid nodes. We have shown that cilia actuated in simple patterns create local circulatory flow patterns that result in mass transfer. In order to achieve a pumping effect, larger-scale flow patterns are desired. In order to demonstrate that cilia can be used with simple asymmetric oscillations to create a significant pumping effect, we performed simulations in which flexible filament cilia were oscillated by a modulated sinusoidal oscillating distributed force. We found that while cilia oscillated by a sinusoidal oscillating force experience symmetric beating patterns and generate no net pumping effect. The same cilia driven by asymmetric sinusoidal oscillating force results in an effective stroke in which the cilia sweep through the fluid in an erect position and a recovery stroke in which they are forced to recover in a bent pattern. This resulted in a significant pumping effect, where a volume of 74% of the cube of the cilium length was pumped with every stroke. We will use this understanding of the physics of oscillating cilia to guide the design of efficient capture and sample preconcentration geometries for target bacteria, in particular Salmonella. Our numerical model validated against our experimental observations will be used to further understand the complex physics of this system under various working parameters not easily accessible in the using experiments, and to guide designs of cilia arrays which are optimized for pumping and capture of targets in complex mixtures.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
D. Owen, M. Ballard, A. Alexeev, P. J. Hesketh, Rapid microfluidic mixing via rotating magnetic microbeads, Sensors and Actuators A Physical, Vol. 251, pp. 84-91 (2016).
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
M. Ballard, D. Owen, Z. G. Mills, P. J. Hesketh, A. Alexeev, Orbiting magnetic microbeads enable rapid microfluidic mixing, Microfluidics & Nanofluidics Vol. 20, pp. 88 (2016).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
S. Hanasoge, D. Owen, M. Ballard, Z. Mills, J. Xu, M. Erickson, P. J. Hesketh, A. Alexeev, Active fluid mixing with magnetic microactuators for capture of Salmonella, Sensing for Agriculture and Food Quality and Safety VIII, Proceedings of SPIE Vol. 9864, Baltimore (2021th April 2016).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
D. Owen, M. Ballard, S. Hanasoge, P. J. Hesketh, A. Alexeev, Efficient capture of particles via rotating magnetic beads in a microfluidic channel, 229th ECS Meeting, San Diego, CA, May 29th -June 3rd, 2016.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
S. K. G. Hanasoge, M. S. Ballard, M. Erickson, Jie Xu, P. J. Hesketh, A. Alexeev, Pumping induced by bio-mimetic magnetic micro-cilia in creeping flows, 230th ECS Meeting, Honolulu, Hawaii, October 2-6th 2016.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
P. J. Hesketh, Ultra-low power MEMS gas sensors and efficient preconcentration using microfluidic devices for Salmonella Biological and Chemical Sensors Summit, La Jolla, CA, Dec. 5-7th (2016).
|
Progress 01/01/15 to 12/31/15
Outputs
Target Audience:
Nothing Reported
Changes/Problems:Due to the limited range of the magnetic bead volume in the channel, we have been investigating cilia which extend a greater distance into the channel, 100's of micrometer, rather than 10 micrometer. This increases our fluid flow volumes by a factor of ten time or more. Magnetic cilia for mixing and capture. Capturing the magnetic micro beads on to the NiFe features as reported in the accomplishments is difficult at higher flow speeds, as the fluid drag forces are higher than the magnetic forces required to hold and manipulate the beads. To resolve this problem, we have developed hair-like, cilia, which extend from the surface, anchored at one end across the fluid channel. The cilia are much bigger in size, compared to the 3 um beads, and therefore stretch across the height of the channel. To perform the capture and mixing the cilia undergo an oscillatory motion. We have demonstrated a reliable and straight forward method for the fabrication of the cilia. The surface of the cilia will be specifically functionalized to enable specific capture. The cilia oscillate from a naturally curved position with an externally magnetic field. The oscillating frequency of the cilia has been controlled by changing the rpm of a spinning magnet. In our experiments we have actuated the cilia up to a frequency of 40Hz. We have successfully demonstrate fluid pumping and mixing effects of the cilia by using an array. Arrays of cilia are placed in opposing directions, in the transverse direction to fluid flow. These pump the fluid in opposite directions thereby mixing it. The primary mode for fluid manipulation is the asymmetric motion of the cilia, which leads to a net pumping of the fluid. What opportunities for training and professional development has the project provided?Training of three graduate students, Mathew Ballard, Zachary Mills, and Drew Owen How have the results been disseminated to communities of interest?see list of publications and conference presentations. What do you plan to do during the next reporting period to accomplish the goals?Future work Objective 1 and 2 Work is currently being done to investigate both modeling and experiments of the capture efficiency and reconcile any differences between these results and the experimental observations. These differences might be due binding probability effectiveness related to the time of contact between the functionalized bead and the Salmonella or strength of the binding forces itself. In addition, electrostatic effects could play a role introducing some repulsive forces, which are a function of the properties of the buffer media, pH and ionic strength. These effect could tend to reduce the probability of target capture onto the functionalized bead. Experiments on the ability for the rotating magnetic bead system to capture fluorescent particles from a fluid using a streptavidin-biotin bond are currently under way and will continue this spring semester. This will provide insight into the design of the large-scale device by showing what fluid and channel conditions are required for greatest capture efficiency. The fluorescent -particles used in these experiments are analogous in size to bacteria. The channel conditions tested in these experiments will be (1) the ratio between magnetic bead diameter and channel height and (2) the spacing between NiFe features. The ratio between bead diameter and channel height is important to study as the taller the channel the greater the flow throughput but also has the potential for less impact by the magnetic bead on the fluid. The spacing will be important to investigate because a tighter spacing between the NiFe features can increase the number of potential capture sites. However, some experimental work has shown that placing NiFe features too close to each other makes the capture of fluorescent particles unstable. Further to improve the processing of larger volumes of fluid, we will fabricate and evaluate rows of functionalized magnetic cilia in the channel. The key advantage of using cilia is that the motion extends through a greater height in the channel than the bead based processing. The surface of the surface will be functionalized with antibodies directed for target specific capture, in this case Salmonella. The captured Salmonella on the cilia can be detected by visually inspecting of the surface of the cilia. The motion of the cilia in the channel will induce turbulent mixing and hence increase the probability of capture. Objective 3 The ultimate goal is to implement the capture with arrays of cilia on a CD platform that can perform the capture in numerous channels simultaneously. This would have particular advantages as we can process very high volumes in a short time. We plan to do a comparison with a commercial immunomagnetic separation unit (Matrix) comparing their unit to ours. Comparisons of the performance of the CD based platform against the commercial system will quantify capture efficiency for model leafy greens inoculated with Salmonella.
Impacts
What was accomplished under these goals?
Objective 1: Modeling Capture of Salmonella with Magnetic Beads In our previous efforts, we had used numerical simulations to find that salmonella can be detected using our device over a very short distance (95% salmonella capture after 200 μm - 5 mm for channels of height ranging from 2-6 times the bead diameter), and that there was not an appreciable dependence of distance to salmonella capture on the velocity of fluid flow through the channel with respect to the magnetic bead velocity (velocity ratio) over moderate values of this velocity ratio. In order to better understand how microchannel geometry affects capture performance, we performed additional simulations with varied the spacing between the soft magnetic discs around which supermagnetic microbeads orbit. We found that increasing spacing increases the length of channel required to capture salmonella. This is as would be expected, as there is more space between orbiting beads for the salmonella to move uncaptured down the channel. Increasing the spacing by a factor of about two still results in capture in under a millimeter in channels twice the height of the bead diameter over the range of velocity ratios studied. Interestingly, we found that when the spacing is increased, a dependence of the capture distance on velocity ratio is developed, with the capture distance increasing with increasing velocity ratio. For the previously studied configuration in which orbiting magnetic beads nearly came into contact with each other, salmonella are captured rapidly no matter the velocity ratio. However, as the spacing is increased and there is significant space for salmonella to weave between orbiting beads, it becomes more vital to capture that the beads orbit fast in comparison to the flow velocity. We previously found that reliable capture of salmonella from all portions of the channel only occurs if the microchannel height is no greater than six times the bead diameter, since for channels taller there will be regions at the top of the channel where the beads cannot disturb the flow enough to draw down salmonella for capture. In order to determine a way to increase flow throughput through each microchannel by further increasing channel height, we studied the effect of diagonal ridges patterned onto the microchannel ceiling on circulation of the salmonella. We demonstrated that the flow circulation pattern created by the diagonal ridges causes salmonella in the channel to circulate around the channel, such that salmonella originating in the upper half of the channel move down to the bottom of the channel. Thus, the channel height could be doubled through use of this device, while still allowing all of the salmonella to come down near the beads for capture. However, the circulatory flow and thus the transverse velocity of the salmonella is no more than about 20% of the axial velocity of flow down the channel, and thus salmonella must flow through a section of channel 2.5 times the perimeter of the channel (approximately 800 μm in our case) for all salmonella to be located in the lower half of the channel at some point. Our current experimental device uses a bead array about 200 μm long, so while this could be done through the use of a longer bead array or alternating sections of beads and diagonal ridges, its incompatibility with our current setup leads it to not currently be a focus of our research. We also used numerical simulations to investigate the feasibility of separating magnetic beads with captured salmonella from those that have not captured salmonella, so as to facilitate detection of salmonella. The proposed method of separation consisted of using a magnetic field to drag beads through the fluid across the channel and separating beads with and without salmonella by the distance they travel across the channel, which is affected by the drag of the attached salmonella. In our simulations, we found that although attached salmonella increase fluid drag and decrease the translation distance across the channel, this difference is only about 5% of the total translation distance, and is not significant enough for reliable separation. Objective 2: Magnetic beads for capture of target Experimental Test Bed System A system was constructed for analyzing the mixing and capture abilities of the rotating beads. This system makes use of electroosmotic flow for precise control of fluid velocity. It also allows for analysis over a much wider array of flow ratios than was previously undertaken. This system uses glass substrates with a different fabrication process flow. A key insight in the development of this process flow was the observation that NiFe could be deposited without an underlying adhesion layer by increasing the chamber temperature during evaporation. In addition to the simplified fabrication, this system also was easier to load with magnetic beads, because any clusters of magnetic beads upon entering the array are dispersed. This system has been used to perform multiple experiments as summarized in the following section. Experimental Results on Capture The ability of the rotating magnetic beads to capture fluorescent particles from a fluid using a streptavidin-biotin bond have been studied over a range of flow rates and bead rotation velocity. The fluorescent particles used in these experiments are analogous to bacteria in size. The particles are captured more efficiently with a higher density of beads in the channel, and at large ratios of bead velocity to fluid velocity. When the fluid velocity is higher than the bead velocity capture is inefficient. The length of the channel also has an impact on collection efficiency. Data is currently being analyzed from the video's taken during the experiments to determine 1) the ratio between magnetic bead diameter and channel height and 2) the spacing between NiFe features for highest capture efficiency. This will provide insight into the design of the large-scale device by showing what fluid and channel conditions are required for greatest capture efficiency. Mixing Experiments An analysis of the mixing effects of rotating beads in the channel has also been performed. In these experiments, the ratio of fluid linear velocity to bead velocity has been varied. The mixing effect was found to be significant only when the ratio of fluid linear velocity to rotating bead linear velocity was less than 0.1. This effect has been confirmed in both experiment and numerical simulations. A journal paper has been submitted to Sensors and Actuators B which is now under review. A longer array with more columns of features and more magnetic beads could produce even greater mixing by having more a longer residence time for the beads to transport fluid across the channel width. This longer array could make it possible to achieve strong mixing at values of u > 0.1.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
M. S. Ballard, D. L. Owen, Z. G. Mills, S. K. G. Hanasoge, P. J. Hesketh, A. Alexeev, Low-concentration Salmonella detection using orbiting magnetic microbeads in a continuous-flow microfluidic device, Summer Biomechanics, Bioengineering and Biotransport Conference, Snowbird Resort, Utah, June 17-20 2015.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
M. S. Ballard, D. L. Owen, Z. G. Mills, S. K. G. Hanasoge, P. J. Hesketh, A. Alexeev, Design of a rapid magnetic microfluidic mixer, Abstract KP2-13, American Physical Society Meeting, Boston, MA, November 22-24th, 2015.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
S. K. G. Hanasoge, D. L. Owen, M. S. Ballard, P. J. Hesketh, A. Alexeev, Magnetically actuated cilia for microfluidic manipulation, Abstract JR9-7, American Physical Society Meeting, Boston, MA, November 22-24th, 2015.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2016
Citation:
D. Owen, S. K. Hanasoge, M. Ballard, Z. Mills, A. Alexeev, P. J. Hesketh, Title: Rapid Microfluidic Mixing via Rotating Magnetic Microbeads, submitted to Sensors and Actuators A (2016).
- Type:
Journal Articles
Status:
Under Review
Year Published:
2016
Citation:
M. Ballard, D. Owen, Z. G. Mills, Peter Hesketh, Alexander Alexeev, A rapid orbiting magnetic bead microfluidic mixer, submitted to Microfluidics Nanofluidics (2016).
- Type:
Other
Status:
Submitted
Year Published:
2016
Citation:
S. Hanasoge, D. Owen, M. Ballard, J. Xu, M. Erickson, A. Alexeev, P. J. Hesketh, "Efficient Preconcentration using Magnetic Beads and Cilia for Bacterial Contamination in Food Samples," NSF Workshop on Food, Energy, and Water Nexus: Transformative Food Technologies to Enhance Sustainability at the FEW Nexus, February 22-25th, Nebraska
|
Progress 01/01/14 to 12/31/14
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Training of graduate and undergraduate students. How have the results been disseminated to communities of interest? Through publications at conferences and workshops. What do you plan to do during the next reporting period to accomplish the goals? Capture experiments and quantification of Salmonella capture on Dynal magnetic beads and funcationalize beads from other vendors of different diamters to optimize capture efficiency. Model Salmonella Capture with Lattice Boltzmann technique and investigate optimum condition for capture in large fluid volumes by varing flow rate and channel dimensions.
Impacts
What was accomplished under these goals?
A key challenge in biosensing is the capture of a target from a complex matrix. We are investigating methods to improve sampling and pre-concentration through efficient bead-based manipulation using magnetic fields. We have assembled a test-bed system for evaluation of permanent magnet and coil based of magnetic field inducted manipulation of microbeads in a microfluidic channel. We have also assembled a Compact-Disc based microfluidic system with magnetic field action on the fluid channels at the disc to provide bead manipulation. Both of these system are imaged with the high power optical microscope to study the bead motions, fluorescent target capture and mixing of fluids in the channels at different flow rates. The test-bed magnetophoresis system capable of controlled transport of rotating super-paramagnetic beads among soft magnetic features on planar substrates. Low aspect-ratio NiFe discs (on the order of hundreds of nm tall, diameter 3 µm) are patterned onto a silicon or glass substrate. A PDMS channel is bonded onto the wafer to create the microfluidic channel. An external permanent magnet attached to a motor provides a magnetic field, which can be rotated at different speeds while magnetizing the NiFe disks in the channel. The super-paramagnetic microbeads (Dynabeads M-280, Invitrogen) are trapped at the poles of the now magnetized soft magnetic discs. Rotation of the external permanent magnet will also rotate the induced magnetic poles in the soft magnetic discs which will in turn rotate the trapped microbeads. As an analogue for bacteria, this system uses biotin-coated fluorescent particles (Fluorspheres, Life Sciences). The super-paramagnetic particles are coated with streptavidin in this set-up as an analogue to antibody coated beads. Fluorescent microspheres were introduced into the channel containing a bed of rotating Dynabead M-280s (2.8 µm diameter). Based upon the geometry of the channel (125 µm wide and 6.5 µm tall) at a volumetric flow rate of 0.2 µL/min. the calculated average velocity of the microspheres in the channel was 4 mm/s. The magnetically trapped M-280 beads were rotating at a speed of 2500 rpm in the channel, corresponding to a linear velocity of 0.4 mm/s. The individually controlled bead transport with synchronized circulating motion provide strong interact between the particles and the flow, which is also good for sample mixing. The CD test-bed employs a disc consisting of an array of circular NiFe magnetic features that are axially symmetric. Sample is driven along numerous axially symmetric micro-channels in a radially outward direction. This pumping occurs under the influence of the centrifugal force created by the rotating disc. Super-paramagnetic beads are first introduced into the rotating device and are manipulated by a uniform external magnetic field. This enables the bead rotation around the magnetic features, thereby enhancing the mixing in the device. This setup is novel in that, it enables continuous high volume sampling and does not require external pumps/valves for fluid handling. The rotating disc enables both the pumping of fluid and bead rotation. Simulation results In order for the microfluidic system to capture Salmonella for extraction and analysis, the microbeads must come into contact with the Salmonella. Numerical simulations of microfluidic mixing were used to quantitatively assess the ability of the microbeads to process all of the fluid in the microchannel, making it likely to come into contact with the target bacteria. Our research is focused on the design of a continuous-flow microfluidic device that uses antibody-functionalized superparamagnetic beads orbiting around soft ferromagnetic discs to sweep through the microchannel and enable rapid capture of Salmonella from the entire fluid volume. We focus on capture of Salmonella, but such a device could be functionalized for capture of other application-specific target cells. We simulate the microfluidic device as a microchannel filled with a pressure-driven viscous fluid, in which suspended Salmonella are modeled as cylinders with spherical caps (2 µm long and 0.5 µm in diameter). The microchannel also contains microbeads of diameter a=2.8 µm orbiting around 3 µm diameter ferromagnetic discs patterned on the channel floor. Periodic boundary conditions in the x (flow) and y(transverse) directions allow us to simulate flow down the channel and a wide channel cross-section, respectively. The z (vertical) direction is subjected to stationary solid wall boundary conditions. We use a lattice Boltzmann method with immersed boundary technique to model the interactions between the fluid and the solid beads and salmonella. The fluid dynamics is modeled using the lattice Boltzmann method(LBM) with interpolated bounce-back boundary conditions applied at the moving solid surfaces of the beads and salmonella based on the velocity of the solid nodes. The solid nodes experience the appropriate resulting forces from the fluid.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
D. Owen, M. Ballard, W. Mao, A. Alexeev, P. J. Hesketh, Magnetic microbeads for sampling and mixing in a microchannel, Proceedings of SPIE, Vol. 8976, #10, February (2014).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
S. Hanasoge, D. Owen, M. Ballard, Z. Mills, A. Alexeev, P. J. Hesketh, Development of CD based micro-fluidics device for high throughput particle capture and sampling, Fall Meeting of the ECS, Cancun, Mexico, October 5-10th (2014).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
P. J. Hesketh, A. Alexeeve, M. Ballard, S. Hanasoge, A. Mahdavifar, Z. Mills, D. Owen Magnetic Field Based Bead Sampling of Bacteria in MicroFluidic System and Low Power MEMS Sensors, Proceedings of ICMEMSS, Chennai, India, paper # MFI,2, December 18-20th (2014)
- Type:
Other
Status:
Published
Year Published:
2014
Citation:
D. Owen, M. Ballard, S. Hanasoge, Z. Mills, P. J. Hesketh, A. Alexeev Development of CD based micro-fluidic device for high throughput capture and sampling, NSF Workshop on Food Safety Global Supply Chain Needs, Alexandria, Virginia, October 29-30th (2014).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
D. Owen, M. Ballard, Z. Mills, S. Hanasoge, P. J. Hesketh, and A. Alexeev. "Salmonella capture using orbiting magnetic microbeads." Bulletin of the American Physical Society, Vol. 59, #20, November 23-25th (2014).
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