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From Macro to Nano: Electrokinetic Transport and Surface Control
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.ORCID iD: 0000-0001-9177-1174
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, the growing and aging population, and the rise of new global threats on human health puts an increasing demand on the healthcare system and calls for preventive actions. To make existing medical treatments more efficient and widely accessible and to prevent the emergence of new threats such as drug-resistant bacteria, improved diagnostic technologies are needed. Potential solutions to address these medical challenges could come from the development of novel lab-on-chip (LoC) for point-of-care (PoC) diagnostics.

At the same time, the increasing demand for sustainable energy calls for the development of novel approaches for energy conversion and storage systems (ECS), to which micro- and nanotechnologies could also contribute.

This thesis has for objective to contribute to these developments and presents the results of interdisciplinary research at the crossing of three disciplines of physics and engineering: electrokinetic transport in fluids, manufacturing of micro- and nanofluidic systems, and surface control and modification. By combining knowledge from each of these disciplines, novel solutions and functionalities were developed at the macro-, micro- and nanoscale, towards applications in PoC diagnostics and ECS systems.

At the macroscale, electrokinetic transport was applied to the development of a novel PoC sampler for the efficient capture of exhaled breath aerosol onto a microfluidic platform.

At the microscale, several methods for polymer micromanufacturing and surface modification were developed. Using direct photolithography in off-stoichiometry thiol-ene (OSTE) polymers, a novel manufacturing method for mold-free rapid prototyping of microfluidic devices was developed. An investigation of the photolithography of OSTE polymers revealed that a novel photopatterning mechanism arises from the off-stoichiometric polymer formulation. Using photografting on OSTE surfaces, a novel surface modification method was developed for the photopatterning of the surface energy. Finally, a novel method was developed for single-step microstructuring and micropatterning of surface energy, using a molecular self-alignment process resulting in spontaneous mimicking, in the replica, of the surface energy of the mold.

At the nanoscale, several solutions for the study of electrokinetic transport toward selective biofiltration and energy conversion were developed. A novel, comprehensive model was developed for electrostatic gating of the electrokinetic transport in nanofluidics. A novel method for the manufacturing of electrostatically-gated nanofluidic membranes was developed, using atomic layer deposition (ALD) in deep anodic alumina oxide (AAO) nanopores. Finally, a preliminary investigation of the nanopatterning of OSTE polymers was performed for the manufacturing of polymer nanofluidic devices.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , xix, 113 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2014:020Theses in philosophy from the Royal Institute of Technology, ISSN 1650-8831
Keyword [en]
microsystem, nanosystem, microfluidic, nanofluidic, surface modification, surface property, electrokinetics, model, simulation, material, polymer, thiol-ene, microfabrication, nanofabrication, micromanufacturing, nanomanufacturing, breath sampling, aerosol precipitation, corona discharge, electrostatic precipitation, grafting chemistry, click chemistry, nanopore, nanoporous membrane, photolithography, photopatterning, photografting, microfluidics, nanofluidics, oste, OSTE+, OSTEmer, lab-on-chip, loc, point-of-care, poc, biocompatibility, diagnostics, breath analysis, fuel cell
National Category
Nano Technology Other Electrical Engineering, Electronic Engineering, Information Engineering Textile, Rubber and Polymeric Materials Other Medical Engineering Polymer Technologies
Research subject
Electrical Engineering; Materials Science and Engineering; Physics; Medical Technology
Identifiers
URN: urn:nbn:se:kth:diva-144994ISBN: 978-91-7595-119-5 (print)OAI: oai:DiVA.org:kth-144994DiVA: diva2:715478
Public defence
2014-05-23, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
RappidNanoGateNorosensor
Funder
Swedish Research CouncilEU, European Research Council
Note

QC 20140509

Available from: 2014-05-09 Created: 2014-05-05 Last updated: 2014-12-04Bibliographically approved
List of papers
1. Modeling and simulation of electrostatically gated nanochannels
Open this publication in new window or tab >>Modeling and simulation of electrostatically gated nanochannels
2013 (English)In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 199, 78-94 p.Article in journal (Refereed) Published
Abstract [en]

Today, despite the growing interest in nanofluidics, the descriptions of the many complex physical phenomena occurring at this scale remain scattered in the literature. Due to the additional complexity encountered when considering electrostatic nanofluidic gating, it is important to regroup several relevant theories and discuss them with regard to this application. In this work, we present a theoretical study of electrostatically gated phenomena and propose a model for the electrostatic gating of ion and molecular transport in nanochannels. In addition to the classical electrokinetic equations, that are reviewed in this work, several relevant phenomena are considered and combined to describe gating effects on nanofluidic properties more accurately. Dynamic surface charging is accounted for and is shown to be an essential element for electrostatic gating. The autoprotolysis of water is also considered to allow for accurate computing of the surface charge. Modifications of the Nernst-Planck equations are considered for more accurate computing of the concentration profiles at higher surface potentials by accounting for ion crowding near charge walls. The sensitivity of several parameters to the electric field and ion crowding is also studied. Each of these models is described separately before their implementation in a finite element model. The model is verified against previous experimental work. Finally, the model is used to simulate the tuning of the ionic current through the nanochannel via electrostatic gating. The influence of the additional models on these results is discussed. Guidelines for potentially better gating efficiencies are finally proposed.

Keyword
Nanofluidics, electrostatic gating, nanofluidic transistor, model, nanochannel, microfluidics
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-124238 (URN)10.1016/j.cis.2013.06.006 (DOI)000326486700007 ()2-s2.0-84885320538 (Scopus ID)
Projects
NanoGate
Funder
Swedish Research Council
Note

QC 20131129

Available from: 2013-06-29 Created: 2013-06-27 Last updated: 2017-12-06Bibliographically approved
2. Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores
Open this publication in new window or tab >>Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores
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2013 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 24, no 1, 015602- p.Article in journal (Refereed) Published
Abstract [en]

Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al2O3) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al2O3 layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 mu m thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al2O3 using ALD.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2013
Keyword
nanopore, ALD, nanofluidic transistor, large surface area electrode, platinum, aluminum oxide, AAO, nanofluidics, microfluidics, lab-on-chip, loc, fuel cell
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-104073 (URN)10.1088/0957-4484/24/1/015602 (DOI)000312272500020 ()2-s2.0-84870523064 (Scopus ID)
Projects
NanoGate
Funder
Swedish Research CouncilEU, European Research Council, 267528VINNOVA
Note

QC 20130110

Available from: 2012-10-26 Created: 2012-10-26 Last updated: 2017-12-07Bibliographically approved
3. Rapid mold-free manufacturing of microfluidic devices with robust and spatially directed surface modifications
Open this publication in new window or tab >>Rapid mold-free manufacturing of microfluidic devices with robust and spatially directed surface modifications
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2014 (English)In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 17, no 4, 773-779 p.Article in journal (Refereed) Published
Abstract [en]

A new method that allows for mold-free, rapid and easy-to-use proto- typing of micro uidic devices comprising channels, access holes and surface modied patterns, is presented. The innovative method is based on direct photolithographic patterning of an o-stoichiometry thiol-ene (OSTE) polymer formulation, tailor-made for photolithography, which oers unprecedented spatial resolution and allow for ecient, robust and reliable, room temperature surface modication and glue-free, covalent room temperature bonding. This mold-free process does not require cleanroom equipment and therefore allows for rapid, i.e. less than one hour, design-fabricate-test cycles, using a material suited for larger scale production. The excellent photolithographic properties of this new OSTE formulation allow for high-resolution patterning in hundreds of micrometers thick layers, 200 m thick in this work. Moreover, we demonstrate robust (covalent) and spatially controlled modication of the microchannel surfaces with a contact angle of 76 degrees to hydrophobic/hydrophilic areas with contact angles of 102 and 43 degrees, respectively.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2014
Keyword
lab-on-chip, microfluidics, photolithography, OSTE polymer, surface modi, oste, oste+, OSTEmer, lab-on-chip, off-stoichiometric thiol-ene
National Category
Nano Technology
Research subject
Biotechnology; Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-124363 (URN)10.1007/s10404-014-1351-9 (DOI)000342454400016 ()2-s2.0-84920255161 (Scopus ID)
Projects
Rappid
Note

QC 20141027

Available from: 2013-06-29 Created: 2013-06-29 Last updated: 2017-12-06Bibliographically approved
4. Off-Stoichiometry Improves Photostructuring of Thiol-Enes Through Diffusion-Induced Monomer Depletion
Open this publication in new window or tab >>Off-Stoichiometry Improves Photostructuring of Thiol-Enes Through Diffusion-Induced Monomer Depletion
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2016 (English)In: Microsystems and Nanoengineering, ISSN 2055-7434, Vol. 2, 15043Article in journal (Refereed) Published
Abstract [en]

Thiol-enes are a group of alternating copolymers with highly ordered networks used in a wide range of applications. Here, “click” chemistry photostructuring in off-stoichiometric thiol-enes is shown to induce microscale polymeric compositional gradients due to species diffusion between non-illuminated and illuminated regions, creating two narrow zones with distinct composition on either side of the photomask feature boundary: a densely cross-linked zone in the illuminated region and a zone with an unpolymerized highly off-stoichiometric monomer composition in the non-illuminated region. By the use of confocal Raman microscopy, it is here explained how species diffusion causes such intricate compositional gradients in the polymer, and how off-stoichiometry results in improved image transfer accuracy in thiol-ene photostructuring. Furthermore, increasing the functional group off-stoichiometry and decreasing photomask feature size is shown to amplify the induced gradients, which potentially leads to a new methodology for microstructuring.

Place, publisher, year, edition, pages
Nature Publishing Group, 2016
Keyword
thiol-ene, oste, OSTEmer, polymer, photopatterning, photolithography, monomer diffusion, click chemistry, Raman confocal microscopy, microfluidics
National Category
Nano Technology Textile, Rubber and Polymeric Materials
Research subject
Electrical Engineering; Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-144992 (URN)10.1038/micronano.2015.43 (DOI)
Note

Updated from accepted to published.

QC 20160216

Available from: 2014-05-05 Created: 2014-05-05 Last updated: 2017-10-02
5. Aerosol sampling using an electrostatic precipitator integrated with a microfluidic interface
Open this publication in new window or tab >>Aerosol sampling using an electrostatic precipitator integrated with a microfluidic interface
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2015 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 212, 344-352 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the development of a point-of-care (PoC) system to capture aerosol from litres of air directly onto a microfluidic lab-on-chip for subsequent analysis is addressed. The system involves an electrostatic precipitator that uses corona charging and electrophoretic transport to capture aerosol droplets onto a microfluidic air-to-liquid interface for downstream analysis. A theoretical study of the governing geometric and operational parameters for optimal electrostatic precipitation is presented. The fabrication of an electrostatic precipitator prototype and its experimental validation using a laboratory-generated aerosolized dye is described. Collection efficiencies were comparable to those of a state-of-the-art Biosampler impinger, with the significant advantage of providing samples that are at least 10 times more concentrated. Finally, we discuss the potential of such a system for breath-based diagnostics.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
breath analysis, poc, point-of-care, lab-on-chip, loc, microfluidics, aerosol, sampling, medical device, diagnostics, electrostatic precipitation, corona discharge
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Medical Biotechnology
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-144986 (URN)10.1016/j.snb.2015.02.008 (DOI)000351017700043 ()2-s2.0-84923763722 (Scopus ID)
Projects
Rappid
Note

QC 20150223

Available from: 2014-05-05 Created: 2014-05-05 Last updated: 2017-12-05Bibliographically approved
6. SURFACE ENERGY MICROPATTERN INHERITANCE FROM MOLD TO REPLICA
Open this publication in new window or tab >>SURFACE ENERGY MICROPATTERN INHERITANCE FROM MOLD TO REPLICA
2014 (English)In: 27th IEEE International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2014), IEEE conference proceedings, 2014, 96-99 p.Conference paper, Published paper (Refereed)
Abstract [en]

We report a novel surface-energy patterning phenomenon, in which a novel polymer composition inherits the surface energy of the medium it is in contact with during polymerization. This surface property mimicking process occurs via spontaneous selective molecular alignment of hydrophilic and hydrophobic monomers mixed into an off-stoichiometry thiol-ene (OSTE) formulation. This single-step method for simultaneous structuring and surface energy micropatterning of polymer structures is potentially more robust and lower cost than state-of-the-art processes requiring post-processing surface modification steps. We further demonstrate the self-assembly of a liquid droplet array on the replicated polymer surfaces.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2014
Series
Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS), ISSN 1084-6999
Keyword
Surface modification, micropatterning, self-assembly, micro array, OSTE, thiol-ene, polymer, microfluidics, lab-on-chip, oste, OSTE+, OSTEmer, loc
National Category
Nano Technology Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:kth:diva-129520 (URN)10.1109/MEMSYS.2014.6765582 (DOI)000352217500025 ()2-s2.0-84899027092 (Scopus ID)978-147993508-6 (ISBN)
Conference
27th IEEE International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2014), San Francisco, CA, USA, 26-30 Jan,2014
Projects
Rappid
Note

QC 20140521

Available from: 2013-10-01 Created: 2013-10-01 Last updated: 2016-04-25Bibliographically approved

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