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  • 1.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Jokilaakso, Nima
    KTH, School of Biotechnology (BIO), Protein Technology.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Björk, P.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Effect of microwave-assisted silanization on sensing properties of silicon nanoribbon FETs2015In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 209, p. 586-595Article in journal (Refereed)
    Abstract [en]

    An important concern with using silicon nanoribbon field-effect transistors (SiNR FET) for ion-sensing is the pH-response of the gate oxide surface. Depending on the application of the FET sensor, this response has to be chemically manipulated. Thus in silicon oxide-gated pH-sensors with integrated sensor and reference FETS, a surface with high pH-sensitivity, compared to the bare gate oxide, is required in the sensor FETs (SEFET), whereas in the reference FETs (REFET) the surface has to be relatively pH-insensitive. In order to control the sensitivity and chemistry of the oxide surface of the nanoribbons, a silanization reagent with a functional group is often self-assembled on the SiNR surface. Choice of a silanization reaction that results in a self-assembled layer on a silicon oxide surface has been studied extensively over the past decades. However, the effect of various self-assembled layers such as monolayers or mixed layers on the electrical response of SiNR FETs in aqueous solution needs to be exploited further, especially for future integrated SEFET/REFET systems. In this work, we have performed a comprehensive study on 3-aminopropyltriethoxysilane (APTES) silanization of silicon oxide surfaces using microwave (MW) heating as a new biocompatible route to conventional methods. A set of complementary surface characterization techniques (ellipsometry, AFM and ATR-FTIR) was used to analyze the properties of the APTES layer deposited on the silicon surface. We have found that a uniform monolayer can be achieved within 10 min by heating the silanization solution to 75 degrees C using MW heating. Furthermore, electrical measurements suggest that little change in device performance is observed after exposure to MW irradiation. Real-time pH measurements indicate that a uniform APTES monolayer not only reduces the pH sensitivity of SiNR FET by passivating the surface silanol groups, but also makes the device less sensitive to cation concentration in the background electrolyte. Our silanization route proves promising for future chemical surface modification of on-chip REFETs.

  • 2.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Griss, P.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Expandable microspheres - surface immobilization techniques2002In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 84, no 2-3, p. 290-295Article in journal (Refereed)
    Abstract [en]

    In this study, a novel component for microfluidics is introduced. Expandable microspheres have been studied for their application in microfluidics. Two methods for selective immobilization of expandable microspheres without the use of mechanical barriers on silicon, including patterning by photolithography and self-assembly based on surface chemistry have been shown. After the immobilization step the microspheres were expanded thermally. The expansion is irreversible and the volume of the microspheres increases more than 60 times. Patterns of microspheres with features as small as 15 pm have successfully been generated by photolithography. By using self-assembly the microspheres can conveniently be immobilized in monolayers. Future applications of the expandable microspheres can be as fluidic components, such as one-shot valves or micropumps, positioning other microcomponents or to enlarge the surface area.

  • 3.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Jonsson, C.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Consecutive microcontact printing - ligands for asymmetric catalysis in silicon channels2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 79, no 1, p. 78-84Article in journal (Refereed)
    Abstract [en]

    Consecutive microcontact printing ( mu CP) has been developed to enable multiple functionalization of silicon surfaces, such as the immobilization of chiral ligands. The technique involves two subsequent printing steps using unstructured poly(methylsiloxane) stamps. The pattern is already defined on the substrate, consisting of etched channels. Hence, no precise alignment is needed between the two printing steps. A carboxylic acid group containing reagent was initially printed onto the silicon oxide surface and transformed to an anhydride. hi the second printing step an ester bond was formed with the hydroxy-functionalized ligand. The formed molecular layers were evaluated by contact angle measurements, scanning electron microscopy (SEM) and electron spectroscopy for chemical analysis (ESCA), indicating that the consecutive mu CP was successful. Initially, printing was performed on planar silicon surfaces but to realize a flow-through microfluidic device for high throughput screening a mu CP technique was developed for etched channels. To verify the technique, hydrophobic valves consisting of octadecyltrichlorosilane were formed using mu CP in deep reactive ion etched channels (50 mum wide and 50 mum deep). The printed hydrophobic patches were visualized by SEM and functioned well. Finally, the consecutive mu CP technique was applied to immobilize the ligand in the channels. The channels were then sealed with a low-temperature bonding technique using an adhesive PDMS film, which does not destroy the printed ligand. In this study mu CP is used in a novel manner. It enables a convenient method for performing complex surface modification of etched structures, which is a frequently appearing problem in biochemical microfluidic systems.

  • 4.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van den Berg, A.
    Microfluidic devices for cellomics: a review2003In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 92, no 3, p. 315-325Article, review/survey (Refereed)
    Abstract [en]

    A review of microfluidic devices for cellomics is presented. After a brief description of the historical background of Lab-on-Chip (LOC) devices, different areas are reviewed. Devices for cell sampling are presented, followed by cell trapping and cell sorting devices based upon mechanical and electrical principles. Subsequently, a popular type of cell sorters, flow cytometers, is considered, followed by a chapter describing devices for cell treatment: cell lysis, poration/gene transfection and cell fusion devices. Finally a number of microfluidic devices for cellular studies are reviewed. The large amount of very recent publications treated in this review indicates the rapidly growing interest in this exciting application area of LOC.

  • 5.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Enoksson, P.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Micromachined flow-through filter-chamber for chemical reactions on beads2000In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 67, no 1-2, p. 203-208Article in journal (Refereed)
    Abstract [en]

    A new flow-through micromachined device for chemical reactions on beads has been designed, manufactured, and characterized. The device has an uncomplicated planar design and microfabrication process. Both nonmagnetic and magnetic beads can be collected in the reaction chamber without the use of external magnets. The sample flow-through volume of liquid or gas is adjustable and unlimited. The device is sealed with Pyrex to allow real time optical detection of the chemical reactions. At a constant pressure of 3 kPa at the inlet the flow rate for water is about 3.5 mu l/min without beads in the filter chamber, for all the designs. The smallest reaction chamber has a volume of 0.5 nl and can collect approximately 50 beads with a diameter of 5.50 mu m. At a constant pressure of 3 kPa at the inlet, the flow rate for water is about 2.0 mu l/min when the reaction chamber is completely packed with beads. Hence, the flow rate decreases with about 40% when the reaction chamber is packed with beads. The flow-through microfluidic device is not sensitive to gas bubbles, and clogging of the filter is rare and reversible. The beads are easy to remove from the reaction chamber making the micromachined flow-through device reusable. A new and simple technique for fluid interconnection is developed.

  • 6.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Griss, P.
    Niklaus, Frank
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hydrophobic valves of plasma deposited octafluorocyclobutane in DRIE channels2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 75, no 1-2, p. 136-141Article in journal (Refereed)
    Abstract [en]

    The suitability of using octafluorocyclobutane (C4F8) patches as hydrophobic valves in microfluidic biochemical applications has been shown. A technique has been developed to generate lithographically defined C4F8 hydrophobic patches in deep reactive ion-etched silicon channels. Some of the advantages of this process are that no specific cleaning of the substrate is required, C4F8 is deposited on the sidewalls and the bottom of the channels, a standard photoresist mask can be used to define the patches, and that it is a fast and convenient dry chemical process performed by a standard inductively coupled plasma etcher using the Bosch process. Different patch lengths (200-1000 mum) of C4F8 were deposited in 50 mum wide channels to evaluate which size is most suitable for microfluidic biochemical applications. The valve function of the hydrophobic patches was tested for the following liquids: DD water, acetone, propanol, bead solution and a mixture used for pyrosequencing of DNA. Patch lengths of 200 mum of C4F8 successfully stopped each solution for at least 20 consecutive times. The C4F8 film resists water for at least 5 h. The hydrophobic valve also resists very high concentrations (25%) of surfactants (Tween 80). C4F8 shows a much higher resistance towards water and surface active solutions than previous hydrophobic patches. However, 50% Tween 80 was not stopped at all by the hydrophobic patch. An applied pressure of 760 Pa at the inlet was needed for water to over-run the hydrophobic patch.

  • 7.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Nilsson, Peter
    KTH, Superseded Departments, Biotechnology.
    Enoksson, P.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A valve-less diffuser micropump for microfluidic analytical systems2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 72, no 3, p. 259-265Article in journal (Refereed)
    Abstract [en]

    The suitability of valve-less micropumps in biochemistry has been shown. Fluids encountered in various biochemical methods that are problematic for other micropumps have been pumped with good performance. The pump is fabricated as a silicon-glass stack with a new process involving three subsequent deep reactive ion etching steps. Some of the main advantages of the valve-less diffuser pump are the absence of moving parts (excluding the pump diaphragm), the uncomplicated planar design, and high pump performance in terms of pressure head and flow rare. In addition, the micropump is self-priming and insensitive to particles and bubbles present in the pumped media. The results show that the valve-less micropump successfully pumps fluids within the viscosity range of 0.001-0.9 N s/m(2). The micropump is not sensitive to the density, ionic strength, or pH of the pumped media. Effective pumping of solutions containing beads of different sizes was also demonstrated. Living cells were pumped without inducing cell damage and no cell adhesion within the pump chamber was found. No valve-less micropump has previously been reported to pump such a wide variety of fluids.

  • 8. Aparicio, Francisco J.
    et al.
    Alcaire, Maria
    Gonzalez-Elipe, Agustin R.
    Barranco, Angel
    Holgado, Miguel
    Casquel, Rafael
    Sanza, Francisco J.
    Griol, Amadeu
    Bernier, Damien
    Dortu, Fabian
    Caceres, Santiago
    Antelius, Mikael
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems. APR Technol AB, Sweden.
    Lapisa, Martin
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems. Bosch Automot Elect, Germany.
    Sohlstrom, Hans
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Dye-based photonic sensing systems2016In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 228, p. 649-657Article in journal (Refereed)
    Abstract [en]

    We report on dye-based photonic sensing systems which are fabricated and packaged at wafer scale. For the first time luminescent organic nanocomposite thin-films deposited by plasma technology are integrated in photonic sensing systems as active sensing elements. The realized dye-based photonic sensors include an environmental NO2 sensor and a sunlight ultraviolet light (UV) A+B sensor. The luminescent signal from the nanocomposite thin-films responds to changes in the environment and is selectively filtered by a photonic structure consisting of a Fabry-Perot cavity. The sensors are fabricated and packaged at wafer-scale, which makes the technology viable for volume manufacturing. Prototype photonic sensor systems have been tested in real-world scenarios. (C) 2016 Elsevier B.V. All rights reserved.

  • 9.
    Bai, Yunpeng
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Weibull, Emilie
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Jönsson, Håkan
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Andersson Svahn, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Interfacing picoliter droplet microfluidics with addressable microliter compartments using fluorescence activated cell sorting2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 194, p. 249-254Article in journal (Refereed)
    Abstract [en]

    Droplet microfluidic platforms have, while enabling high-throughput manipulations and the assaying of single cell scale compartments, been lacking interfacing to allow macro scale access to the output from droplet microfluidic operations. Here, we present a simple and high-throughput method for individually directing cell containing droplets to an addressable and macro scale accessible microwell slide for downstream analysis. Picoliter aqueous droplets containing low gelling point agarose and eGFP expressing Escherichia coli (E. coli) are created in a microfluidic device, solidified to agarose beads and transferred into an aqueous buffer. A Fluorescence activated cell sorter (FACS) is used to sort agarose beads containing cells into microwells in which the growth and expansion of cell colonies is monitored. We demonstrate fast sorting and high accuracy positioning of sorted 15 μm gelled droplet agarose beads into microwells (14 × 48) on a 25 mm × 75 mm microscope slide format using a FACS with a 100 μm nozzle and an xy-stage. The interfacing method presented here enables the products of high-throughput or single cell scale droplet microfluidics assays to be output to a wide range of microtiter plate formats familiar to biological researchers lowering the barriers for utilization of these microfluidic platforms.

  • 10. Bora, Tanujjal
    et al.
    Fallah, H.
    Chaudhari, M.
    Apiwattanadej, T.
    Harun, S. W.
    Mohammed, W. S.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Controlled side coupling of light to cladding mode of ZnO nanorod coated optical fibers and its implications for chemical vapor sensing2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 202, p. 543-550Article in journal (Refereed)
    Abstract [en]

    Controlled light coupling from surrounding to the cladding mode of zinc oxide (ZnO) nanorod coated multimode optical fiber induced by the light scattering properties of the nanorod coating and their applications of sensing are reported here. A dense and highly ordered array of ZnO nanorods is grown on the cladding of silica fibers by using low temperature hydrothermal process and the effect of the hydrothermal growth conditions of the nanorods on the light scattering and coupling to the optical fibers is experimentally investigated. The nanorod length and its number per unit area are found to be most crucial parameters for the optimum side coupling of light into the fibers. Maximum excitation of the cladding mode by side coupling of light is obtained with ZnO nanorods of length similar to 2.2 mu m, demonstrating average coupling efficiency of similar to 2.65%. Upon exposure to different concentrations of various chemical vapors, the nanorod coated fibers demonstrated significant enhancement in the side coupled light intensity, indicating the potential use of these ZnO nanorod coated fibers as simple, low cost and efficient optical sensors. The sensor responses to methanol, ethanol, toluene and benzene vapor were investigated and compared, while the effect of humidity in the sensing environment on the sensor performance was explored as well.

  • 11. Bose, I.
    et al.
    Ohlander, Anna
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Kutter, C.
    Russom, Aman
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    An integrated all foil based micro device for point of care diagnostic applications2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 259, p. 917-925Article in journal (Refereed)
    Abstract [en]

    Point-of-Care (POC) diagnostics often fail to meet the market requirements of low cost and advanced functionality, and are often limited to lateral flow based serological diagnostics with reduced sensitivity and specificity. We report here on an integrated microfluidic absorbance measurement device fabricated by roll-to-roll (R2R) compatible manufacturing processes, suitable for low cost POC systems. It is a device exclusively made of foils and takes external light from a low cost LED and converts the point light source to a homogeneous light via a foil based optical filter at the bottom of the device. The light is converted to an electrical signal by an amorphous organic semiconductor (OSC) material, integrated with screen-printed carbon finger on top of the device for electrical measurement. As a proof of principle, we demonstrate DNA hybridization assay, where the target DNA is coupled to magnetic beads for absorbance measurement. The device successfully distinguishes between matched and mismatched DNA hybridization and can differentiate between 1 μM, 50 nM and 2.5 nM DNA target concentrations. The inherent characteristics of the substrates and R2R fabrication concept significantly reduce the cost, making it suitable for POC applications at resource-limited settings. 

  • 12. Chen, Bin
    et al.
    Sun, Xi
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xie, Yongshu
    TICT based fluorescence "turn-on" hydrazine probes2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 199, p. 93-100Article in journal (Refereed)
    Abstract [en]

    Fluorescence "turn-on" probes PC3 and C3 with weak background emissions were developed for hydrazine sensing. The aldehyde and dicyanovinyl groups were used as the recognition units for PD and C3, respectively. Because of low reactivity of the aldehyde group, the fluorescence of PC3 was enhanced by only ca. 93 folds upon addition of a large amount of 1646 eq. hydrazine. In contrast, 0 exhibited fluorescence enhancement by ca. 239 folds upon addition of only 1.3 eq. hydrazine, and thus it showed high sensitivity towards hydrazine, with the detection limit of 7 ppb. In aqueous systems, it also works well with improved selectivity for hydrazine over CN-. The weak fluorescence of PC3 and 0 can be ascribed to twisted intramolecular charge transfer (TICT) processes by the combination of the bulky diphenylamino and 9-anthryl units, which were well demonstrated by theoretical calculations, viscosity dependent fluorescence, and fluorescence decay behaviour. Addition of hydrazine induced the disappearance of the TICT deactivation pathway, resulting in the observed fluorescence enhancement. It can be concluded that the combination of the bulky diphenylamino and 9-anthryl units is an effective approach for developing fluorescence turn-on hydrazine probes based on the TICT mechanism.

  • 13. Chen, Y. C.
    et al.
    Brazier, J. J.
    Yan, Mingdi
    Department of Chemistry, Portland State University.
    Bargo, P. R.
    Prahl, S. A.
    Fluorescence-based optical sensor design for molecularly imprinted polymers2004In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 102, no 1, p. 107-116Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo model was developed to analyze the sensitivity and the performance of a fluorescence-based molecularly imprinted polymer (MIP) sensor. The MIP sensor consisted of highly cross-linked polyurethane containing anthracene binding sites coated on a transparent substrate. The optical properties of MlPs, the quantum yields of anthracene within MIPs, and the fluorescence of MlPs were measured. The rebinding capacity of the MIPs was about 1 mumol/g or roughly seven times binding rate of non-imprinted polymers. The MIP fluorescence emission at 404 nm was measured for thicknesses ranging from 100 to 2000 mum containing templated anthracene concentrations ranging from 60 to 600 ppm for excitation at 358 nm. The emission agreed with model predictions within 15%. This sensing system could only distinguish anthracene down to 15 ppm due to fluorescence from the polymer matrix. To make a fluorescence-based MIP sensor that is capable of detecting one part per billion analyte concentration with a 200 mum thick MIP film, our model suggests that imprinted polymers would need to have an absorption coefficient less than 0.001 cm(-1), or have a quantum yield 10(5) times lower than that of the analyte at the detection wavelength.

  • 14.
    da Silva Granja, Granja
    et al.
    Loughborough University.
    Sandström, Niklas
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Efimov, Igor
    Loughborough University.
    Ostanin, Victor P
    Cambridge University.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Klenerman, David
    Cambridge University.
    Ghosh, Sourav
    Loughborough University.
    Characterisation of particle-surface interactions via anharmonic acoustic transduction2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 272, p. 175-184Article in journal (Refereed)
  • 15.
    Gatty, Hithesh K.
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Leijonmarck, Simon
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Antelius, Mikael
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Roxhed, Niclas
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    An amperometric nitric oxide sensor with fast response and ppb-level concentration detection relevant to asthma monitoring2015In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 209, p. 639-644Article in journal (Refereed)
    Abstract [en]

    A MEMS-based amperometric nitric oxide (NO) gas sensor is reported in this paper. The sensor is designed to detect NO gas for the purpose of asthma monitoring. The unique property of this sensor lies in the combination of a microporous high-surface area electrode that is coated with Nafion (TM), together with a liquid electrolyte. The sensor is able to detect gas concentrations of the order of parts-per-billion (ppb) and has a measured NO sensitivity of 0.045 nA/ppb and an operating range between 25 and 65% relative humidity. The settling time of the sensor is measured to 8s. The selectivity to interfering gases such as ammonia (NH3) and carbon monoxide (CO) was high when placing an activated carbon fiber filter above the sensor. The ppb-level detection capability of this sensor combined with its relatively fast response, high selectivity to CO and NH3 makes the sensor potentially applicable in gas monitoring for asthma detection.

  • 16. Ghaani, M.
    et al.
    Rovera, C.
    Pucillo, F.
    Ghaani, M. R.
    Olsson, Richard T.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Scampicchio, M.
    Farris, S.
    Determination of 2,4-diaminotoluene by a bionanocomposite modified glassy carbon electrode2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 277, p. 477-483Article in journal (Refereed)
    Abstract [en]

    This work describes the development of a modified glassy carbon electrode (GCE) for the selective determination of 2,4-diaminotoluene (TDA), a primary aromatic amines (PAAs) that can be formed in food packaging materials including aromatic polyurethane (PU) adhesives. The electrode's surface was modified with multi-walled carbon nanotubes (MWCNTs), MWCNTs in chitosan (CS), and gold nanoparticles (AuNPs). The highest current response was achieved with AuNPs/MWCNTs-CS/GC electrodes, which exhibited an oxidation peak of 9.87 μA by cyclic voltammetry (CV), compared with 1.39 μA of the bare GCE. A detection limit of 35 nM was estimated by amperometry experiments. The oxidation of TDA was strongly dependent on the pH of the medium, having maximum sensitivity at pH ∼ 7. From a mechanistic point of view, the diffusion coefficient of TDA (D = 6.47 × 10−4 cm2 s−1) and the number of electrons (n ≈ 2) involved in the catalytic oxidation of TDA at the surface of the AuNPs/MWCNTs-CS/GCE were determined. The practical utility of this nanocomposite modified electrode was demonstrated by migration studies from conventional food packaging materials. 

  • 17. Ghosh, Sourav K.
    et al.
    Sandström, Niklas
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Ostanin, V.P
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Klenerman, D.
    Guha, A.
    Simple and ultrafast resonance frequency and dissipation shift measurements using a fixed frequency drive2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 281, p. 960-970Article in journal (Refereed)
    Abstract [en]

    A new method for determination of resonance frequency and dissipation of a mechanical oscillator is presented. Analytical expressions derived using the Butterworth-Van Dyke equivalent electrical circuit allow the determination of resonance frequency and dissipation directly from each impedance datapoint acquired at a fixed amplitude and frequency of drive, with no need for numerical fitting or measurement dead time unlike the conventional impedance or ring-down analysis methods. This enables an ultrahigh time resolution and superior noise performance with relatively simple instrumentation. Quantitative validations were carried out successfully against the impedance analysis method for inertial and viscous loading experiments on a 14.3 MHz quartz crystal resonator (QCR). Resonance frequency shifts associated with the transient processes of quick needle touches on a thiol self-assembled-monolayer functionalised QCR in liquid were measured with a time resolution of 112 μs, which is nearly two orders of magnitude better than the fastest reported quartz crystal microbalance. This simple and fast fixed frequency drive (FFD) based method for determination of resonance frequency and dissipation is potentially more easily multiplexable and implementable on a single silicon chip delivering economies of scale.

  • 18. Gu, Bobo
    et al.
    Yin, Ming-Jie
    Zhang, A. Ping
    Qian, Jin-Wen
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Fiber-optic metal ion sensor based on thin-core fiber modal interferometer with nanocoating self-assembled via hydrogen bonding2011In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 160, no 1, p. 1174-1179Article in journal (Refereed)
    Abstract [en]

    A new fiber-optic metal ion sensor based on a thin-core fiber modal interferometer (TCFMI) is presented. Poly(4-vinylpyridine) (P4VP) and poly(acrylic acid) (PAA) are layer-by-layer deposited on the side surface of the TCFMI via hydrogen bonding for the detection of metal ion in aqueous solutions. Ultraviolet-visible (UV-vis) absorption spectroscopy is employed to monitor the self-assembly process, and the thickness and morphology of the nanocoating are characterized by scanning electron microscopy (SEM). When the sensor is immersed into the aqueous solutions containing metal ions, the refractive index (RI) of the nanocoating is changed because of the association of metal ions with the nanocoating, which was verified by energy dispersive X-ray (EDX). Based on the RI sensing capability of TCFMI, one can detect the concentration of metal ions through the measurement of the dip wavelength of the sensor's transmission spectrum. The experiment results exhibit that the sensor is reusable and with a fast response in a wide metal ion concentration range (10 nM-0.1 M). The limit of detection (LOD) of the sensor is around 9.6 nM experimentally.

  • 19.
    Haraldsson, Klas Tommy
    et al.
    Department of Chemical and Biological Engineering, ECCH 111, UCB424, University of Colorado.
    Hutchison, J.
    Department of Chemical and Biological Engineering, ECCH 111, UCB424, University of Colorado.
    Sebra, Robert
    Department of Chemical and Biological Engineering, ECCH 111, UCB424, University of Colorado.
    Good, Brian
    Department of Chemical and Biological Engineering, ECCH 111, UCB424, University of Colorado.
    Anseth, Kristi
    Department of Chemical and Biological Engineering, ECCH 111, UCB424, University of Colorado.
    Bowman, Christopher
    Department of Chemical and Biological Engineering, ECCH 111, UCB424, University of Colorado.
    3D Polymeric Microfluidic Device Fabrication via Contact Liquid Photolithographic Polymerization (CLiPP)2006In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 113, no 1, p. 454-460Article in journal (Refereed)
    Abstract [en]

    In this contribution, a new method for the fabrication of complex polymeric microfluidic devices is presented. The technology, contact liquid photolithographic polymerization (CLIPP). overcomes many of the draw backs associated kith other rapid prototyping schemes, such as limited materials choices and time-consuming microassembly protocols. CUPP shares many traits with other photolithographic methods, but three distinct features: (i) liquid photoresists in contact with the photomask. (ii) readily removed sacrificial Materials. and (iii) living radical processes, enable multiple polymeric chemistries and mechanical properties while simultaneously enabling facile fabrication of 3D geometries and surface chemistry control. This contribution details fabrication techniques and methods for the fabrication of high aspect ratio posts covalently bonded to a polymeric substrate, an array of independently stacked bars on top of perpendicular bars, multiple undercut structures fabricated simultaneously, and a complex 3D geometry with intertwined channels.

  • 20. Hussain, Tanveer
    et al.
    Vovusha, Hakkim
    Kaewmaraya, Thanayut
    Amornkitbamrung, Vittaya
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 255, p. 2713-2720Article in journal (Refereed)
    Abstract [en]

    Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16 eV), (0.70-1.58 eV) and (0.22-0.96 eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules.

  • 21. Islam, M. S.
    et al.
    Hussain, Tanveer
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden, Univ Queensland, Australia.
    Rao, G. S.
    Panigrahi, P.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Augmenting the sensing aptitude of hydrogenated graphene by crafting with defects and dopants2016In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 228, p. 317-321Article in journal (Refereed)
    Abstract [en]

    Density functional theory (DFT) level calculations were performed to study the interaction of hydrogenated graphene (CH) monolayer towards methane (CH4) gas molecules. The structural, electronic and gas sensing properties of pure, defected and light metal-doped CH monolayer were investigated. For the pristine CH, the estimated binding energy of CH4 fell short of the desired physisorption range and limit its gas sensing application at ambient conditions. However, upon crafting defects on pure CH layer by introducing hydrogen vacancies, a sharp increase in adsorption energies were observed when the CH4 molecules approached the defected sites of CH. Further, the effect of metal doping was studied by uniformly distributing light metal adatoms on CH monolayer which significantly enhanced the CH4 adsorption. To have better accuracy in calculating adsorption energies, we have incorporated van der Waals type corrections to our calculations for these weakly interacting systems.

  • 22. Jeanneret, Stephane
    et al.
    Crespo, Gaston A.
    Afshar, Majid Ghahraman
    Bakker, Eric
    GalvaPot, a custom-made combination galvanostat/potentiostat and high impedance potentiometer for decentralized measurements of ionophore-based electrodes2015In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 207, p. 631-639Article in journal (Refereed)
    Abstract [en]

    We report here on a portable, custom-made instrument for decentralized measurements with ionophore based electrodes. It allows one to perform most common electrochemical protocols based on applied current or potential as well as zero current potentiometry measurements. Each protocol is customizable via a programmable interface by use of either an external PC or a touch screen panel on the device. The programmable interface provides flexibility to trigger peripheral devices for the additional implementation of actuators, pumps and other external devices in the electrochemical routines.

    To characterize the electronic performance of the instrument, three different electrochemical protocols were used with ionophore based electrodes and compared with a commercial work station: (1) open circuit potentiometric measurements with calcium ion-selective membranes; (2) chronoamperometry based on three successive pulses with simultaneous control of fluidic delivery by a peristaltic pump and switching valve, followed by on board current integration to obtain a coulometric readout; (3) a chronopotentiometric protocol using protamine selective membranes with current pulses of 5-s duration, including an automatic computation of the time-derivative to find the transition time as the analytical signal. At 500 g, the instrument is portable yet sufficiently versatile for performing and analyzing most electrochemical measurements without the need for an external computer. It may become an attractive tool for applications in environmental and clinical analysis where field portability, flexibility and integration are desired.

  • 23.
    Melin, Jessica
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Roxhed, Niclas
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Gimenez, Guillem
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Griss, Patrick
    KTH, Superseded Departments, Signals, Sensors and Systems.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A liquid-triggered liquid microvalve for on-chip flow control2004In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 100, no 3, p. 463-468Article in journal (Refereed)
    Abstract [en]

    This work introduces a novel surface tension and geometry based liquid-triggered liquid microvalve for on-chip liquid flow control. The simultaneous presence of two liquid plugs at the uncomplicated valve junction triggers the further movement of the liquids and overcomes the stop valve function of the device, thereby providing a precise means of timing liquid movement on-chip. The generic structure was shown to successfully function and forms the basis for several novel and useful functions, including fluidic AND gates, contactless on-chip liquid sample control, timing of independent processes on the same microchip, bubble-free joining of liquids, all of which pose great challenges in the area of microfluidics. The device may be applied to chemical analysis, drug discovery, medical diagnostics and biochemistry.

  • 24.
    Molnár, Mátyás
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Chen, Y.
    Friberg, Peter
    Gan, L.-M.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Effects of K+ and Na+ ions on the fluorescence of colloidal CdSe/CdS and CdSe/ZnS quantum dots2011In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 155, no 2, p. 823-830Article in journal (Refereed)
    Abstract [en]

    In this work we studied the effects of K+ and Na+ ions on fluorescence properties of the colloidal quantum dots (QDs). It was found that the fluorescence intensity was enhanced when low concentration of ions was introduced to QD solutions, while it became weakened when ion concentrations reached their physiological levels in many bio environments. Such fluorescence changes can be attributed to interactions between QD surface ligands and ions as well as the Coulomb potential of ions that displaces the wave functions of the electron and hole confined inside the QD. These results are important for understanding the influence of different biological environments, such as extracellular and intracellular compartments, on optical properties of colloidal QDs.

  • 25.
    Pardon, Gaspard
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Ladhani, Laila
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Sandström, Niklas
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Ettori, Maxime
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Lobov, Gleb
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Aerosol sampling using an electrostatic precipitator integrated with a microfluidic interface2015In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 212, p. 344-352Article in journal (Refereed)
    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.

  • 26.
    Parmeggiani, Matteo
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dev, Apurba
    KTH, School of Engineering Sciences (SCI), Applied Physics. Uppsala University, Uppsala, Sweden.
    Björk, P.
    Linnros, Jan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Electrokinetic-assisted gating in a microfluidic integrated Si nanoribbon ion sensor for enhanced sensitivity2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 262, p. 974-981Article in journal (Refereed)
    Abstract [en]

    Using the electrokinetic principle, we demonstrate a novel approach to modulate the response of an ion sensitive silicon-nanoribbon field-effect-transistor, effectively manipulating the device sensitivity to a change in surface potential. By using the streaming potential effect we show that the changes in the surface potential induced by e.g. a pH change can be accurately manipulated in a microfluidic-integrated chip leading to an enhanced response. By varying the flow velocity and the biasing condition along the microfluidic channel, we further demonstrate that the pH response from such a device can also be suppressed or even reversed as a function of the flow velocity and the biasing configuration. Experiments performed with different pH buffer shows that the sensor response can be enhanced/suppressed by several times in magnitude simply by using the streaming potential effects. A mathematical description is also presented for qualitative assessment of the electrokinetic influence on the gate terminal under different biasing condition. The approach presented here shows the prospect to exploit the electrokinetic modulation for developing highly sensitive nanoscale biosensors. © 2018 Elsevier B.V.

  • 27. Prajapati, C. S.
    et al.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Semiconductor Materials, HMA.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bhat, N.
    Honeycomb type ZnO nanostructures for sensitive and selective CO detection2017In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 252, p. 764-772Article in journal (Refereed)
    Abstract [en]

    Excellent sensing performance for CO gas is demonstrated using inexpensive sensor devices based on honeycomb type ZnO nanostructures, fabricated by colloidal lithography and lift-off process. This newly proposed method for gas sensors is cost effective and provides significant enhancement of both sensitivity and selectivity of CO detection. Honeycomb type ZnO nano films developed in ∼21 nm ZnO layer consisting of 1 μm period hexagonal lattice of air-holes with diameter varying from ∼600–900 nm are investigated for CO sensing. These structures are fabricated by a combination of self-assembly of polystyrene (PS) spheres, their size reduction by oxygen plasma and magnetron-sputtering of ZnO followed by PS mask removal. The hole diameter and hence the width of ZnO honeycomb walls are determined by size reduction of PS spheres. Fabricated ZnO honeycomb type sensors show superior sensing performance compared to planar ZnO films, and response as high as ∼81.2% at 300 °C for a 3 ppm CO with a detection resolution of 500 ppb and response and recovery times of ∼180 and ∼210 s, respectively, were obtained. The repeatability of the observed results is confirmed and in addition, the CO selectivity is shown for gas mixtures consisting of CH4, H2S, CO2, NO2, SO2 and H2. The developed nanostructuring method is generic and can be adapted for improving performance of other metal-oxide based gas sensors.

  • 28.
    Renberg, Björn
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Hedhammar, My
    Mimicking silk spinning in a microchip2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 195, p. 404-408Article in journal (Refereed)
    Abstract [en]

    Nature's high performance material, spider silk, is formed during the passage of a protein solution through a spinning duct. Herein we present a microfluidic device with dual laminar mobile phases where silk formation can be mimicked and investigated. Recombinant miniature spidroins, with or without the pH-switching N-terminal domain, were used to investigate spinning conditions into silk-like fibers using this setup.

  • 29.
    Ribet, Federico
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    De Pietro, Luca
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Roxhed, Niclas
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Stemme, Göran
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Gas diffusion and evaporation control using EWOD actuation of ionic liquid microdroplets for gas sensing applications2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 267, p. 647-654Article in journal (Refereed)
    Abstract [en]

    The lifetime of electrochemical gas sensors suffers from electrolyte evaporation and from the impracticality to perform recalibration. To tackle these issues, a prototype of a microfabricated gas diffusion controlling system, based on coplanar electrowetting-on-dielectric (EWOD) actuation of ionic liquid microdroplets, is presented. The system is designed to be integrated with electrochemical gas sensors to allow on-demand sealing of the sensing chamber from the environment. The MEMS device can be electrically toggled between an open and a closed state, in which the microdroplets are used to cover or uncover the openings of a perforated membrane connecting to the sensing compartment, respectively. This ON/OFF diffusion-blocking valve mechanism potentially allows for recalibration and for liquid electrolyte evaporation reduction when the sensor is not in use, thus extending the gas sensor lifetime. A one order of magnitude reduction of evaporation rate and a more than three orders of magnitude reduction of gas diffusion time were experimentally demonstrated. Ionic liquid movement can be performed with an applied AC voltage as low as 18 V, using super-hydrophobic cover plates to facilitate droplet motion. Furthermore, the shown ionic liquid micro-droplet manipulation provides a robust and low voltage platform for digital microfluidics, readily adaptable to serve different applications.

  • 30.
    Swerin, Agne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Mira, I.
    Ink-jettable paper-based sensor for charged macromolecules and surfactants2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 195, p. 389-395Article in journal (Refereed)
    Abstract [en]

    The use of metachromatic dye-based formulations for the preparation of inkjettable prototype indicators suitable for the detection of charged macromolecules, surfactants or other low molecular weight molecules was investigated. Such indicators were based on the use of metachromatic o-toluidine blue (OTB) that undergoes a characteristic change in color (from blue to pink) upon interaction with anionic macromolecules. When applied onto absorbing substrates such as paper and paperboard, solutions containing OTB and the same dye in the presence of potassium polyvinyl sulfate (KPVS), proved to indicate negatively charged polymers and cationic surfactants. The colorimetric responses suggest a detection limit and sensitivity both are in the order of 1 mM of charged species but can be further improved. Interactions between active species in the indicators and some of the additives in inkjettable formulations (surfactant and humectants) interfered with the mechanism by which an OTB/KVPS-based system work only to a minor degree and could be overcome by priming the substrate. An OTB-based system was formulated into an inkjettable formulation that, once applied to a substrate, was showed to indicate charged polymers and surfactants. This concept has the potential for sensing/indication of other charged macromolecules, such as carboxylates and polyphosphates, which are relevant in biomedical (e.g. fouling due to microbial activity), packaging applications (e.g. migration or release of compounds, food spoilage), microfluidic devices or a simple dipstick application to indicate the presence of charged components.

  • 31. Tang, Y.
    et al.
    Ding, Y.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, T.
    Zhang, W.
    Xie, Y.
    Acylation of dipyrromethanes at the α and β positions and further development of fluorescent Zn2+ probes2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 206, p. 291-302Article in journal (Refereed)
    Abstract [en]

    The acylation of 5-aryl dipyrromethanes afforded products with interestingly rich substitution modes, i.e.; α- and β-monoacylated (modes a and b), and α, α′-, α, β′- and β, β′-diacylated (modes c-e). Especially, the β- and β, β′-acylation modes are unprecedented. And most of these products can be synthesized at a gram scale. The anisoyl substituted 5-(4-cyanophenyl) dipyrromethanes (1a-1e) were oxidized with DDQ. Thus, 1a and 1b afforded the corresponding dipyrrins 1a-DPR, and 1b-DPR. More interestingly, the diacylated ones 1c-1e could not be oxidized by DDQ. Instead, 1c-OH-1e-OH were obtained with a hydroxyl group attached to the 5-position. 1a-DPR-1e-OH were further developed as fluorescence turn-on Zn2+ probes. 1d-OH showed the highest sensitivity, with a detection limit of 1.5 × 10-8 M, and it was successfully applied in Zn2+ imaging in Hela cells. Furthermore, single crystals of two Zn2+ complexes were obtained and analyzed by X-ray diffraction.

  • 32.
    Vastesson, Alexander
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Guo, Maoxiang
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Haraldsson, Tommy
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems. KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Polymer Nanoliter Well Arrays for Liquid Storage and Rapid On-demand Electrochemical Release2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 267, p. 111-118Article in journal (Refereed)
    Abstract [en]

    Polymer microfluidic systems are of increasing importance in several applications in biomedicine and biosensing. The integrated encapsulation, storage, and controlled release of small amounts of liquid in such systems remains an unresolved technical challenge. Here, we report two methods for the room-temperature and adhesive-free sealing of 1–330 nanoliter volumes of liquid in off-stoichiometry thiol-ene polymer well arrays by spontaneous bonding to 200 nm thin gold films. Sealed well arrays were stored for more than one month in a liquid environment with <10% liquid loss, and for more than one week in air with minimal loss. We demonstrated that controlling the electrical potential and polarity over encapsulated wells allowed for selecting one of two well opening mechanisms: slow anodic electrochemical etching, or rapid electrolytic gas pressure-induced bursting of the gold film. The results may find potential applications in diagnostic testing, in vivo drug delivery, or in spatio-temporal release of chemical compounds in biological assays.

  • 33. Wang, J.
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, J.
    Tian, H.
    Modulating a D-Π-A type diarylethene for on-demand Cu2+ check via photo-switchable detection range and sensitivity2018In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 257, p. 77-86Article in journal (Refereed)
    Abstract [en]

    Detection range and sensitivity are two important parameters in a sensing system. Unfortunately, in common sensory systems, wide detection range always suffers from low sensitivity and vice versa. Thus, it becomes more and more desirable to design sensors with both wide detection range and high sensitivity. Here, we report a sensory system based on a photo-switchable D-π-A type diarylethene (SDE), which presents both wide detection range and high sensitivity under alternate light modulation. The D-π-A structure endows the sensor with high energy level of HOMO, which enabled the oxidation of both photoisomer SDEo/SDEc by Cu2+. While the discrepancy in energy levels of oxidation potentials in SDE photoisomers leads to their different reactivity, or in another word, sensitivity towards Cu2+. The inherent oxidative cycloreversion of SDEc to SDEo, on the other hand, provides a possibility that two photoisomers would detect Cu2+ in different working concentrations. The open form was employed for the detection of Cu2+ in a wider concentration range (0–13.0 equivalent) with relatively lower sensitivity (6.4 × 10−7 M). While the closed form was able to probe Cu2+ in lower concentration (0–3.0 equivalent) with higher sensitivity (6.6 × 10−9 M). Based on this photo-switchable sensing activity, a molecular multimeter of variable detection range for Cu2+ was then constructed.

  • 34. Yang, Lin
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Qu, Yi
    Qu, Weisong
    Zhang, Xiao
    Hang, Yandi
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hua, Jianli
    Red turn-on fluorescent phenazine-cyanine chemodosimeters for cyanide anion in aqueous solution and its application for cell imaging2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 203, p. 833-847Article in journal (Refereed)
    Abstract [en]

    Two chemodosimeters PDMI and PMI for cyanide detection were designed and synthesized based onphenazinecyanine dyes with N-methyl indolium group as receptor unit. According to the specific reactivity of indolium C-N+ bond against cyanide anion, both of them featured high sensitivity with detectionlimit of 1.4 mu M and 200 nM, respectively, and high selectivity against other anions. The quenching effecton phenazine-cyanine fluorophore by strong intramolecular charge transfer (ICT) from phenazine donorto indolium receptor made both PDMI and PMI non-emissive at the original state. After addition ofcyanide, the ICT effect decreased and vanished leading to dramatic " off-on" fluorescence enhancement. PDMI which proceeded bilateral electrophilic reaction toward cyanide anion provided an emission signal at 580 nm in HEPES buffer with naked-eye detectable color change. Probe PMI utilized an unreactiveformyl group instead of one reactive N-methyl indolium group as the electron-withdrawing component. Due to the unilateral recognition process for cyanide the ICT orientation of PMI was redirectedthus exhibited fluorescence enhancement with maximum emission at 630 nm. Meanwhile, PMI wasapplied for monitoring intracellular cyanide in Hela cells and proved to achieve "off-on" fluorescentsignal confirmed by confocal laser scanning microscopic imaging.

  • 35. Álvarez, Jesús
    et al.
    Sola, Laura
    Cretich, Marina
    Swann, Marcus J.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Volden, Tormod
    Chiari, Marcella
    Hill, Daniel
    Real time optical immunosensing with flow-through porous alumina membranes2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 202, p. 834-839Article in journal (Refereed)
    Abstract [en]

    Through the presentation of analytical data from bioassay experiments, measured by polarimetry, we demonstrate for the first time a real time immunoassay within a free standing macroporous alumina membrane. The 200 nm nominal pore diameter of the membrane enables flow-through, thereby providing an ideal fluidic platform for the targeted delivery of analytes to bioreceptors immobilized on the pore walls, enabling fast sensing response times and the use of small sample volumes (<100 μL). For the immunoassay, the pore walls were first coated with the functional copolymer, copoly(DMA-NAS) using a novel coupling process, before immobilization of the allergen protein, β-lactoglobulin, by spotting. The immuno-assay then proceeded with the binding of the primary and secondary antibody cognates, rabbit anti-β-lactoglobulin and anti-rabbit IgG respectively. Through the use of streptavidin coated quantum dots as refractive index signal enhancers, a noise floor for individual measurements of 3.7 ng/mL (25 pM) was obtained, with an overall statistical, or formal assay LOD of 33.7 ng/mL (225 pM), for total assay time below 1 h.

1 - 35 of 35
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