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Monolithic PDMS passband filters for fluorescence detection
KTH, School of Biotechnology (BIO), Nano Biotechnology.ORCID iD: 0000-0001-5232-0805
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2010 (English)In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 10, no 15, 1987-1992 p.Article in journal (Refereed) Published
Abstract [en]

We present the fabrication and characteristics of monolithically integrated ink dyed poly(dimethylsiloxane) (PDMS) filters for optical sensing in disposable lab-on-a-chip. This represents a migration of auxillary functions onto the disposable chip with the goal of producing truly portable systems. Filters made from commercially available ink (Pelikan) directly mixed into PDMS oligomer without the use of any additional solvents were patterned with standard soft lithography technologies. Furthermore, a fabrication process based on capillary forces is presented allowing PDMS coloration of arbitrary shapes. Different filters of varying thickness fabricated using red, green and blue ink in four different concentrations were characterized. The optimal performance was found with filter thicknesses of 250 mm and ink to PDMS ratios of 0.1 (mL ink : mL PDMS oligomer) resulting in a transmittance ranging from -15.1 dB to -12.3 dB in the stopband and from -4.0 dB to -2.5 dB in the passband. Additionally, we demonstrate the robustness of this approach as the ink dyed PDMS filters do not exhibit temporal ageing due to diffusion or autofluorescence. We also show that such filters can easily be integrated in fluorescence systems, with stopbands efficient enough to allow fluorescence measurements under non-optimal conditions (broadband excitation, 180 degrees configuration). Integrated ink dyed PDMS filters add robust optical functionalities to disposable microdevices at a low cost and will enable the use of these devices for a wide range of fluorescence and absorbance based biological and chemical analysis.

Place, publisher, year, edition, pages
2010. Vol. 10, no 15, 1987-1992 p.
Keyword [en]
National Category
Industrial Biotechnology
URN: urn:nbn:se:kth:diva-29482DOI: 10.1039/c003575kISI: 000279851200015ScopusID: 2-s2.0-77954619141OAI: diva2:395138
EU, FP7, Seventh Framework Programme, (FP7/2007-2013)/ERC 209243
QC 20110204Available from: 2011-02-04 Created: 2011-02-02 Last updated: 2011-02-25Bibliographically approved
In thesis
1. Droplet microfluidics for high throughput biological analysis
Open this publication in new window or tab >>Droplet microfluidics for high throughput biological analysis
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many areas of biological research increasingly perform large-scale analyses.  In genomics the entire gene repertoire of an organism is analyzed.  Proteomics attempts to understand the function and expression patterns of all proteins in a cell or organism.  Cell biologists study large numbers of single cells to understand the heterogeneity of cell populations.  In biotechnology and synthetic biology researchers search for new functional biomolecules in large libraries of biomolecular diversity e.g. for uses in medicine or bioprocessing.  More and more all of these fields employ high throughput methods to achieve the scale of analysis necessary.

Miniaturization and parallelization provide routes towards high throughput analysis, which have proven successful for microelectronics as well as for DNA sequencing.  For the analysis of cells and biomolecules, native to an aqueous environment, miniaturization and parallelization hinges on the handling and parallel processing of very small amounts of water.  Droplet microfluidics utilizes stable picoliter (water) droplets contained in inert fluorinated oils as compartments in which to isolate and analyze cells, molecules or reactions.  These droplets can be manipulated, detected and analyzed at rates of thousands per second in microfluidic modules combining top-down microscale fabrication with the self-assembly of droplets of exact size.

The studies constituting this thesis involve new droplet based biomolecular and single cell assays, manipulation techniques and device fabrication methods to extend the capabilities of droplet microfluidics for high throughput biological analysis.

The first paper in the thesis describes a novel analysis method for studying the low abundant biomarkers present on the surface individual cells at resolutions not available by flow cytometry, the current gold standard of single cell analysis.  The use of a fluorescent optical dye code enabled the analysis of several single cell samples concurrently, improving throughput.

Further a deterministic lateral displacement module, providing passive separation of droplets by size in a microfluidic circuit at more than twice higher rates than previously achievable was demonstrated.  Using this module, droplets were separated for cell occupancy based on a cell induced droplet size transformation, which couples a biological property of the droplet contents to a physical property of the droplet.  This effect, which enables passive separation of at high throughput, indicates a potential novel assay format for clone selection.

One important feature of droplets for encapsulated single cell analysis is retention of secreted molecules providing a genotype-phenotype link.  With the objective of detecting antibody molecules secreted by hybridoma for selection, Paper III demonstrates the adaption of a homogeneous fluorescence polarization based, “mix-incubate-read”, assay for antibody detection.  In the final paper of the thesis the development of inexpensive and robust optical filters monolithically integrated in the microfluidic chip is reported. These defined filters enable integration of multiple optical filters in a polymer microfluidic device.

Overall, droplet microfluidics combines techniques for handling and manipulating millions of discrete biocompatible picoliter compartments per hour with dedicated assays for biomolecule and single cell analysis. The scale of analysis that this enables is certain to impact life science research.


Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 90 p.
Trita-BIO-Report, ISSN 1654-2312 ; 2011:3
Microfluidics, Droplet microfluidics, High throughput biology, Single cell analysis, Hydrodynamic separation, Enzyme amplification, Fluorescence polarization, Microfabrication
National Category
Industrial Biotechnology
Research subject
SRA - Molecular Bioscience
urn:nbn:se:kth:diva-30463 (URN)978-91-7415-858-8 (ISBN)
Public defence
2011-03-18, F2, Linstedtsvägen 26, KTH, Stockholm, 06:09 (English)
QC 20110225Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2011-02-25Bibliographically approved

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