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Dahlberg, T., Stangner, T., Hanqing, Z., Wiklund, K., Lundberg, P., Edman, L. & Andersson, M. (2018). 3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers. Scientific Reports, 8(1), Article ID 3372.
Open this publication in new window or tab >>3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 3372Article in journal (Refereed) Published
Abstract [en]

We report a novel method for fabrication of three-dimensional (3D) biocompatible micro-fluidic flow chambers in polydimethylsiloxane (PDMS) by 3D-printing water-soluble polyvinyl alcohol (PVA) filaments as master scaffolds. The scaffolds are first embedded in the PDMS and later residue-free dissolved in water leaving an inscription of the scaffolds in the hardened PDMS. We demonstrate the strength of our method using a regular, cheap 3D printer, and evaluate the inscription process and the channels micro-fluidic properties using image analysis and digital holographic microscopy. Furthermore, we provide a protocol that allows for direct printing on coverslips and we show that flow chambers with a channel cross section down to 40 x 300 μm can be realized within 60 min. These flow channels are perfectly transparent, biocompatible and can be used for microscopic applications without further treatment. Our proposed protocols facilitate an easy, fast and adaptable production of micro-fluidic channel designs that are cost-effective, do not require specialized training and can be used for a variety of cell and bacterial assays. To help readers reproduce our micro-fluidic devices, we provide: full preparation protocols, 3D-printing CAD files for channel scaffolds and our custom-made molding device, 3D printer build-plate leveling instructions, and G-code.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Other Materials Engineering Other Engineering and Technologies not elsewhere specified Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-144631 (URN)10.1038/s41598-018-21638-w (DOI)000425500300044 ()
Funder
Swedish Research Council, 2013-5379The Kempe Foundations, JCK-1622
Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-08-16Bibliographically approved
Wiklund, K., Zhang, H., Stangner, T., Singh, B., Bullitt, E. & Andersson, M. (2018). A drag force interpolation model for capsule-shaped cells in fluid flows near a surface. Microbiology, 164(4), 483-494
Open this publication in new window or tab >>A drag force interpolation model for capsule-shaped cells in fluid flows near a surface
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2018 (English)In: Microbiology, ISSN 1350-0872, E-ISSN 1465-2080, Vol. 164, no 4, p. 483-494Article in journal (Refereed) Published
Abstract [en]

We report an interpolation model to calculate the hydrodynamic force on tethered capsule-shaped cells in micro-fluidic flows near a surface. Our model is based on numerical solutions of the full Navier–Stokes equations for capsule-shaped objects considering their geometry, aspect ratio and orientation with respect to fluid flow. The model reproduced the results from computational fluid dynamic simulations, with an average error of <0.15 % for objects with an aspect ratio up to 5, and the model exactly reproduced the Goldman approximation of spherical objects close to a surface. We estimated the hydrodynamic force imposed on tethered Escherichia coli cells using the interpolation model and approximate models found in the literature, for example, one that assumes that E. coli is ellipsoid shaped. We fitted the 2D-projected area of a capsule and ellipsoid to segmented E. coli cells. We found that even though an ellipsoidal shape is a reasonable approximation of the cell shape, the capsule gives 4.4 % better agreement, a small difference that corresponds to 15 % difference in hydrodynamic force. In addition, we showed that the new interpolation model provides a significantly better agreement compared to estimates from commonly used models and that it can be used as a fast and accurate substitute for complex and computationally heavy fluid dynamic simulations. This is useful when performing bacterial adhesion experiments in parallel-plate flow channels. We include a MATLAB script that can track cells in a video time-series and estimate the hydrodynamic force using our interpolation formula.

Place, publisher, year, edition, pages
Microbiology Society, 2018
Keywords
E. coli, adhesion, Goldman’s approximation, tethered cells, micro-fluidics
National Category
Other Physics Topics Other Biological Topics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-144499 (URN)10.1099/mic.0.000624 (DOI)29509130 (PubMedID)2-s2.0-85045149561 (Scopus ID)
Available from: 2018-02-05 Created: 2018-02-05 Last updated: 2018-08-16Bibliographically approved
Stangner, T., Dahlberg, T., Svenmarker, P., Zakrisson, J., Wiklund, K., Oddershede, L. B. & Andersson, M. (2018). Cooke-Triplet-Tweezers: More compact, robust and efficient optical tweezers. Optics Letters, 43(9), 1990-1993
Open this publication in new window or tab >>Cooke-Triplet-Tweezers: More compact, robust and efficient optical tweezers
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2018 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 9, p. 1990-1993Article in journal (Refereed) Published
Abstract [en]

We present a versatile three-lens optical design to improve the overall compactness, efficiency, and robustness for optical tweezers based applications. The design, inspired by the Cooke–Triplet configuration, allows for continuous beam magnifications of 2–10× , and axial as well as lateral focal shifts can be realized without switching lenses or introducing optical aberrations. We quantify the beam quality and trapping stiffness and compare the Cooke–Triplet design with the commonly used double Kepler design through simulations and direct experiments. Optical trapping of 1 and 2 μm beads shows that the Cooke–Triplet possesses an equally strong optical trap stiffness compared to the double Kepler lens design but reduces its lens system length by a factor of 2.6. Finally, we demonstrate how a Twyman–Green interferometer integrated in the Cooke–Triplet optical tweezers setup provides a fast and simple method to characterize the wavefront aberrations in the lens system and how it can help in aligning the optical components perfectly.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-145899 (URN)10.1364/OL.43.001990 (DOI)000431179400013 ()29714728 (PubMedID)
Available from: 2018-03-21 Created: 2018-03-21 Last updated: 2018-06-09Bibliographically approved
Zhang, H., Stangner, T., Wiklund, K. & Andersson, M. (2018). Object plane detection and phase retrieval from single-shot holograms using multi-wavelength in-line holography. Applied Optics, 57(33), 9855-9862
Open this publication in new window or tab >>Object plane detection and phase retrieval from single-shot holograms using multi-wavelength in-line holography
2018 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 57, no 33, p. 9855-9862Article in journal (Refereed) Published
Abstract [en]

Phase retrieval and the twin-image problem in digital in-line holographic microscopy can be resolved by iterative reconstruction routines. However, recovering the phase properties of an object in a hologram requires an object plane to be chosen correctly for reconstruction. In this work, we present a novel multi-wavelength iterative algorithm to determine the object plane using single-shot holograms recorded at multiple wavelengths in an in-line holographic microscope. Using micro-sized objects, we verify the object positioning capabilities of the method for various shapes and derive the phase information using synthetic and experimental data. Experimentally, we built a compact digital in-line holographic microscopy setup around a standard optical microscope with a regular RGB-CCD camera and acquired holograms of micro-spheres, E. coli, and red blood cells, which are illuminated using three lasers operating at 491 nm, 532 nm, and 633 nm, respectively. We demonstrate that our method provides accurate object plane detection and phase retrieval under noisy conditions, e.g., using low-contrast holograms with an inhomogeneous background. This method allows for automatic positioning and phase retrieval suitable for holographic particle velocimetry, and object tracking in biophysical or colloidal research. 

Place, publisher, year, edition, pages
Optical Society of America, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-152612 (URN)10.1364/AO.57.009855 (DOI)000450620700019 ()30462021 (PubMedID)
Funder
The Kempe FoundationsMagnus Bergvall Foundation
Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2018-12-19Bibliographically approved
Stangner, T., Hanqing, Z., Tobias, D., Krister, W. & Andersson, M. (2017). Step-by-step guide to reduce spatial coherence of laser light using a rotating ground glass diffuser. Applied Optics, 56(19), 5427-5435
Open this publication in new window or tab >>Step-by-step guide to reduce spatial coherence of laser light using a rotating ground glass diffuser
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2017 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 19, p. 5427-5435Article in journal (Refereed) Published
Abstract [en]

Wide field-of-view imaging of fast processes in a microscope requires high light intensities motivating the use of lasers as light sources. However, due to their long spatial coherence length, lasers are inappropriate for such applications, as they produce coherent noise and parasitic reflections, such as speckle, degrading image quality. Therefore, we provide a step-by-step guide for constructing a speckle-free and high-contrast laser illumination setup using a rotating ground glass diffuser driven by a stepper motor. The setup is easy to build, cheap, and allows a significant light throughput of 48%, which is 40% higher in comparison to a single lens collector commonly used in reported setups. This is achieved by using only one objective to collect the scattered light from the ground glass diffuser. We validate our setup in terms of image quality, speckle contrast, motor-induced vibrations, and light throughput. To highlight the latter, we record Brownian motion of micro-particles using a 100x oil immersion objective and a high-speed camera operating at 2000 Hz with a laser output power of only 22 mW. Moreover, by reducing the objective magnification to 50x, sampling rates up to 10,000 Hz are realized. To help readers with basic or advanced optics knowledge realize this setup, we provide a full component list, 3D-printing CAD files, setup protocol, and the code for running the stepper motor.

Place, publisher, year, edition, pages
Optical Society of America, 2017
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-135625 (URN)10.1364/AO.56.005427 (DOI)000404745800041 ()
Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2018-08-15Bibliographically approved
Zhang, H., Stangner, T., Wiklund, K., Rodrigues, A. & Andersson, M. (2017). UmUTracker: a versatile MATLAB program for automated particle tracking of 2D light microscopy or 3D digital holography data. Computer Physics Communications, 219, 390-399
Open this publication in new window or tab >>UmUTracker: a versatile MATLAB program for automated particle tracking of 2D light microscopy or 3D digital holography data
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2017 (English)In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 219, p. 390-399Article in journal (Refereed) Published
Abstract [en]

We present a versatile and fast MATLAB program (UmUTracker) that automatically detects and tracks particles by analyzing video sequences acquired by either light microscopy or digital in-line holographic microscopy. Our program detects the 2D lateral positions of particles with an algorithm based on the isosceles triangle transform, and reconstructs their 3D axial positions by a fast implementation of the Rayleigh-Sommerfeld model using a radial intensity profile. To validate the accuracy and performance of our program, we first track the 2D position of polystyrene particles using bright field and digital holographic microscopy. Second, we determine the 3D particle position by analyzing synthetic and experimentally acquired holograms. Finally, to highlight the full program features, we profile the microfluidic flow in a 100 gm high flow chamber. This result agrees with computational fluid dynamic simulations. On a regular desktop computer UmUTracker can detect, analyze, and track multiple particles at 5 frames per second for a template size of 201 x 201 in a 1024 x 1024 image. To enhance usability and to make it easy to implement new functions we used object-oriented programming. UmUTracker is suitable for studies related to: particle dynamics, cell localization, colloids and microfluidic flow measurement.

Program summary

Program title: UmUTracker Program Files doi: http://dx.doi.org/10.17632/fkprs4s6xp.1

Licensing provisions: Creative Commons by 4.0 (CC by 4.0)

Programming language: MATLAB Nature of problem: 3D multi-particle tracking is a common technique in physics, chemistry and biology. However, in terms of accuracy, reliable particle tracking is a challenging task since results depend on sample illumination, particle overlap, motion blur and noise from recording sensors. Additionally, the computational performance is also an issue if, for example, a computationally expensive process is executed, such as axial particle position reconstruction from digital holographic microscopy data. Versatile robust tracking programs handling these concerns and providing a powerful post-processing option are significantly limited.

Solution method: UmUTracker is a multi-functional tool to extract particle positions from long video sequences acquired with either light microscopy or digital holographic microscopy. The program provides an easy-to-use graphical user interface (GUI) for both tracking and post-processing that does not require any programming skills to analyze data from particle tracking experiments. UmUTracker first conduct automatic 2D particle detection even under noisy conditions using a novel circle detector based on the isosceles triangle sampling technique with a multi-scale strategy. To reduce the computational load for 3D tracking, it uses an efficient implementation of the Rayleigh-Sommerfeld light propagation model. To analyze and visualize the data, an efficient data analysis step, which can for example show 4D flow visualization using 3D trajectories, is included. Additionally, UmUTracker is easy to modify with user customized modules due to the object-oriented programming style.

Additional comments: Program obtainable from https://sourceforge.net/projects/umutracker/

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Image processing, Digital holographic microscopy, Particle tracking velocimetry, Microfluidics
National Category
Computer Vision and Robotics (Autonomous Systems) Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-131047 (URN)10.1016/j.cpc.2017.05.029 (DOI)000407984100035 ()
Available from: 2017-02-03 Created: 2017-02-03 Last updated: 2018-08-15Bibliographically approved
Zhang, H., Stangner, T., Wiklund, K. & Andersson, M.Object plane detection and phase retrieval from single-shot holograms using multi-wavelength in-line holography.
Open this publication in new window or tab >>Object plane detection and phase retrieval from single-shot holograms using multi-wavelength in-line holography
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Phase retrieval and the twin-image problem in digital in-line holographic microscopy can be resolvedby iterative reconstruction routines. However, recovering the phase properties of an object in a hologramneeds an object plane to be chosen correctly for reconstruction. In this work, we present a novelmulti-wavelength Gerchberg-Saxton algorithm to determine the object plane using single-shot hologramsrecorded with multiple wavelengths in an in-line holographic microscope. For micro-sized objects, weverify the object positioning capabilities of the method for various shapes and derive the phase informationusing synthetic and experimental data. Experimentally, we built a compact digital in-line holographicmicroscopy setup around a standard optical microscope with a regular RGB-CCD camera andacquire holograms of micro-spheres, E. coli and red blood cells, that are illuminated using three lasersoperating at 491nm, 532nm and 633nm, respectively. We demonstrate that our method provides accurateobject plane detection and phase retrieval under noisy conditions, e.g., using low-contrast hologramswithout background normalization. This method allows for automatic positioning and phase retrievalsuitable for holographic particle velocimetry, and object tracking in biophysical or colloidal research.

Keywords
digital holographic microscopy, image reconstruction, multiple wavelengths
National Category
Biophysics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-150685 (URN)
Available from: 2018-08-15 Created: 2018-08-15 Last updated: 2018-08-15
Enevold, J., Dahlberg, T., Stangner, T., Tang, S., Lindh, E. M., Gracia-Espino, E., . . . Edman, L.Tunable two-dimensional patterning of a semiconducting C60 fullerene film using a spatial light modulator.
Open this publication in new window or tab >>Tunable two-dimensional patterning of a semiconducting C60 fullerene film using a spatial light modulator
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(English)Manuscript (preprint) (Other academic)
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-166406 (URN)
Available from: 2019-12-16 Created: 2019-12-16 Last updated: 2019-12-18
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5475-1422

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