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  • 1. Abraham, T.
    et al.
    Kumpulainen, A.
    Xu, Z.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Claesson, Per M.
    KTH, Superseded Departments, Chemistry.
    Masliyah, J.
    Polyelectrolyte-mediated interaction between similarly charged surfaces: Role of divalent counter ions in tuning surface forces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 26, p. 8321-8327Article in journal (Refereed)
    Abstract [en]

    The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw similar to 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale R-G of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Angstrom due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH similar to8.0-9.0, in contrast to the case of 3 MM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Angstrom followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.

  • 2. Addicoat, Matthew
    et al.
    Atkin, Rob
    Canongia Lopes, José Nuno
    Costa Gomes, Margarida
    Firestone, Millicent
    Gardas, Ramesh
    Halstead, Simon
    Hardacre, Christopher
    Hardwick, Laurence J.
    Holbrey, John
    Hunt, Patricia
    Ivaništšev, Vladislav
    Jacquemin, Johan
    Jones, Robert
    Kirchner, Barbara
    Lynden-Bell, Ruth
    MacFarlane, Doug
    Marlair, Guy
    Medhi, Himani
    Mezger, Markus
    Pádua, Agílio
    Pantenburg, Isabel
    Perkin, Susan
    Reid, Joshua E. S. J.
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Saha, Satyen
    Shimizu, Karina
    Slattery, John M.
    Swadźba-Kwaśny, Malgorzata
    Tiwari, Shraeddha
    Tsuzuki, Seiji
    Uralcan, Betul
    van den Bruinhorst, Adriaan
    Watanabe, Masayoshi
    Wishart, James
    Structure and dynamics of ionic liquids: general discussion2018In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 206, no 0, p. 291-337Article in journal (Refereed)
  • 3.
    Alvarez-Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tribological Properties Mapping: Local Variation in Friction Coefficient and Adhesion2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 50, no 3, p. 387-395Article in journal (Refereed)
    Abstract [en]

    Tribological properties mapping is a new technique that extracts friction coefficient and adhesion maps obtained from lateral atomic force microscope (LAFM) images. By imaging the surface systematically as a function of load, a series of images can be tiled, and pixelwise fitted to a modified Amontons' Law to obtain friction coefficient and adhesion maps. This removes the ambiguity of friction contrast in LAFM imaging which can be a function of the load used for imaging. In ambient laboratory, air and tetradecane, a sample of Vancron(A (R))40, commercial powder metallurgical tool alloy containing nitrogen, have been scanned using a standard silicon cantilever in order to obtain tribological data. The tribological properties mapping provides unique information regarding the heterogeneous alloy microstructure as well as shedding light on the tribological behavior of the alloy.

  • 4.
    Alvarez-Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sabibi, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ejnermark, Sebastian
    Ekman, Lars
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Role of Microstructure on Pitting  Corrosion Initiation of an Experimental Tool Alloy: A Peak Force QNM Atomic Force Micrscopy StudyManuscript (preprint) (Other academic)
  • 5.
    Alvarez-Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Chemistry, Materials and Surfaces, SP Technical Research Institute of Sweden.
    Note: Determination of torsional spring constant of atomic force microscopy cantilevers: Combining normal spring constant and classical beam theory2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, no 9, p. 096102-096102-3Article in journal (Refereed)
    Abstract [en]

    A technique has been developed for the calculation of torsional spring constants for AFM cantilevers based on the combination of the normal spring constant and plate/beam theory. It is easy to apply and allow the determination of torsional constants for stiff cantilevers where the thermal power spectrum is difficult to obtain due to the high resonance frequency and low signal/noise ratio. The applicability is shown to be general and this simple approach can thus be used to obtain torsional constants for any beam shaped cantilever.

  • 6.
    Alvarez-Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wallqvist, Viveca
    Kjellin, Mikael
    Leungo, Gustavo
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Nordgren, Niklas
    Nanomechanical Properties of Human Skin Studies by AFM and a Novel Hair IndenterManuscript (preprint) (Other academic)
  • 7. Arvidsson, M.
    et al.
    Ringstad, L.
    Skedung, L.
    Duvefelt, Kenneth
    KTH, School of Industrial Engineering and Management (ITM).
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Feeling fine - the effect of topography and friction on perceived roughness and slipperiness2017In: Biotribology, ISSN 2352-5738, Vol. 11, p. 92-101Article in journal (Refereed)
    Abstract [en]

    (1) Background. To design materials with specific haptic qualities, it is important to understand both the contribution of physical attributes from the surfaces of the materials and the perceptions that are involved in the haptic interaction. (2) Methods. A series of 16 wrinkled surfaces consisting of two similar materials of different elastic modulus and 8 different wrinkle wavelengths were characterized in terms of surface roughness and tactile friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using free magnitude estimation. Friction experiments were performed both by participants and by a trained experimenter with higher control. (3) Results and discussion. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 μm and roughness above 100 μm. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent. The friction is related to contact area between finger and material. Somewhat surprising was that the material with the higher elastic modulus was perceived as more slippery. A concluding finding was that the flat (high friction) reference surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction components.

  • 8.
    Arvidsson, Martin
    et al.
    Department of Psychology, Stockholm University, Sweden.
    Berglund, Birgitta
    Department of Psychology, Stockholm University, Sweden.
    Skedung, Lisa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Aikala, Maiju
    Oy Keskuslaboratorio - Centrallaboratorium Ab (KCL), Espoo, Finland.
    Danerlöv, Katrin
    Institute for Surface Chemistry (YTK), Stockholm, Sweden.
    Kettle, John
    Oy Keskuslaboratorio - Centrallaboratorium Ab (KCL), Espoo, Finland.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Multidimensional psychophysics: surface feel of printing paper as a function of physical propertiesManuscript (preprint) (Other academic)
  • 9. Arvidsson, Martin
    et al.
    Ringstad, Lovisa
    Skedung, Lisa
    Duvefelt, Kenneth
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Rutland, Mark W
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Feeling fine – the effect of topography and friction on perceived roughness and slipperiness2016Manuscript (preprint) (Other academic)
    Abstract [en]

    To be able to design materials with specific haptic qualities, it is important to understand not only the contribution of physical attributes from the surfaces of the materials, but also the perceptions that are involved in the haptic interaction with the materials. A series of 16 wrinkled surfaces with two different materials (Young’s modulus of 1,600 and 20,000 psi, respectively) and 8 different wrinkle wavelengths (30‑120 µm, and two unwrinkled reference surfaces) were thus characterized in terms of surface roughness and finger friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using the method of free magnitude estimation. Five of the sixteen participants conducted friction measurements during their perceived slipperiness session, and an experimenter conducted friction measurements in a separate experiment with higher experimental control. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 µm and roughness above 100 µm. In the interval between 30 and 50 µm it is hard to discriminate between the wavelengths, these surfaces also exhibit the highest slipper­iness and the lowest roughness. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not indepen­dent; which is also supported by an increased friction between 80‑100 µm that corresponds well with both a change in slipperiness and in roughness. The increased friction in this specific wavelength region is related to an increased contact area between finger and material. Somewhat surprising was the fact that the material with the higher Young’s modulus was perceived as more slippery, especially for the smaller wavelengths, this is also the range where it was difficult to differentiate between the wave­lengths. A concluding finding was that the flat (high friction) references surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface rough­ness and friction components.

  • 10.
    Arvidsson, Martin
    et al.
    Department of Psychology, Stockholm University.
    Skedung, Lisa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Aikala, Maiju
    Oy Keskuslaboratorio - Centrallaboratorium Ab.
    Danerlöv, Katrin
    YKI Institute for Surface Chemistry.
    Kettle, John
    Oy Keskuslaboratorio - Centrallaboratorium Ab.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Berglund, Birgitta
    Department of Psychology, Stockholm University.
    Haptic perception of fine surface texture: Psychophysical interpretation of the multidimensional spaceManuscript (preprint) (Other academic)
  • 11.
    Asencio, Rubén Alvarez
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Cranston, Emily D.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Atkin, Rob
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ionic Liquid Nanotribology: Stiction Suppression and Surface Induced Shear Thinning2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 26, p. 9967-9976Article in journal (Refereed)
    Abstract [en]

    The friction and adhesion between pairs of materials (silica, alumina, and polytetrafluoroethylene) have been studied and interpreted in terms of the long-ranged interactions present. In ambient laboratory air, the interactions are dominated by van der Waals attraction and strong adhesion leading to significant frictional forces. In the presence of the ionic liquid (IL) ethylammonium nitrate (EAN) the van der Waals interaction is suppressed and the attractive/adhesive interactions which lead to "stiction" are removed, resulting in an at least a 10-fold reduction in the friction force at large applied loads. The friction coefficient for each system was determined; coefficients obtained in air were significantly larger than those obtained in the presence of EAN (which ranged between 0.1 and 0.25), and variation in the friction coefficients between systems was correlated with changes in surface roughness. As the viscosity of ILs can be relatively high, which has implications for the lubricating properties, the hydrodynamic forces between the surfaces have therefore also been studied. The linear increase in repulsive force with speed, expected from hydrodynamic interactions, is clearly observed, and these forces further inhibit the potential for stiction. Remarkably, the viscosity extracted from the data is dramatically reduced compared to the bulk value, indicative of a surface ordering effect which significantly reduces viscous losses.

  • 12. Atkin, Rob
    et al.
    Li, Hua
    Sweeney, James
    Elbourne, Aaron
    Webber, Grant
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Warr, Gregory Goodman
    Effect of surface nanostructure and ion structure on the nanotribology of the graphite: Ionic liquid interface2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal (Other academic)
  • 13. Attard, Phil
    et al.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). Ytkemiska Institutet, Sweden.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). Ytkemiska Institutet, Sweden.
    Thermal calibration of photodiode sensitivity for atomic force microscopy2006In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, no 11Article in journal (Refereed)
    Abstract [en]

    The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.

  • 14. Attard, Phil
    et al.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Stiernstedt, johanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Measurement of friction coefficients with the atomic force microscope2007In: PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY / [ed] Meyer, E; Hegner, M; Gerber, C; Guntherodt, HJ, Bristol: Iop Publishing Ltd , 2007Conference paper (Refereed)
    Abstract [en]

    A new axial method for measuring the friction coefficient with the atomic force microscope is given. This axial method requires no calibration steps and is performed simultaneously with a normal force measurement by measuring the difference between the constant compliance slopes of the extend and retract force curves. The algorithm can be applied retrospectively to extract the friction coefficient from preexisting force measurements. Results are in quantitative agreement with the more established lateral method. The method can be used for both tipped cantilevers and for attached spherical probes.

  • 15.
    Badal Tejedor, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Swede.
    Nordgren, N.
    Schuleit, M.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Swede.
    Millqvist-Fureby, A.
    Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure2015In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 486, no 1-2, p. 315-323Article in journal (Refereed)
    Abstract [en]

    Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.

  • 16.
    Badal Tejedor, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. RISE Research Institutes of Sweden, Sweden.
    Nordgren, Niklas
    Schuleit, Michael
    Millqvist-Fureby, Anna
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 46, p. 13180-13188Article in journal (Refereed)
    Abstract [en]

    Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), alpha-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture due to the fast condensation kinetics leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive effect under the same ambient conditions. The markedly different behavior detected by force measurements clearly shows the sticky and nonsticky propensity of the materials and allows a mechanistic description.

  • 17.
    Badal Tejedor, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Stockholm, Sweden..
    Nordgren, Niklas
    RISE Res Inst Sweden, Stockholm, Sweden..
    Schuleit, Michael
    Novartis Pharma AG, Basel, Switzerland..
    Millqvist-Fureby, Anna
    RISE Res Inst Sweden, Stockholm, Sweden..
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Stockholm, Sweden..
    AFM colloidal probe measurements implicate capillary condensation in punch-particle surface interactions during tableting2019In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal (Other academic)
  • 18.
    Badal Tejedor, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Intitutes of Sweden.
    Pazesh, Samaneh
    Nordgren, Niklas
    Schuleit, Michael
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Intitutes of Sweden.
    Alderborn, Göran
    Millqvist-Fureby, Anna
    Milling induced amorphisation andrecrystallization of α-lactose monohydrate2018In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 537, no 1-2, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the alpha-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed alpha-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between un-processed a-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spraydried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition.

  • 19. Bazant, Martin
    et al.
    Bennewitz, Roland
    Bocquet, Lydéric
    Brilliantov, Nikolay
    Dey, Ranabir
    Drummond, Carlos
    Dryfe, Robert
    Girault, Hubert
    Hatzell, Kelsey
    Kornev, Konstantin
    Kornyshev, Alexei A.
    Kratochvilova, Irena
    Kucernak, Anthony
    Kulkarni, Mohit
    Kumar, Sunny
    Lee, Alpha
    Lemay, Serge
    Medhi, Himani
    Mount, Andrew
    Mugele, Frieder
    Perkin, Susan
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Schatz, George
    Schiffrin, David
    Smela, Elisabeth
    Smirnov, Evgeny
    Urbakh, Michael
    Yaroshchuk, Andriy
    Electrotunable wetting, and micro- and nanofluidics: general discussion2017In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 199, no 0, p. 195-237Article in journal (Refereed)
  • 20.
    Benselfelt, Tobias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Cranston, Emily D.
    Department of Chemical Engineering, McMaster University.
    Ondaral, Sedat
    Department of Pulp and Paper Technology, Karadeniz Technical University.
    Johansson, Erik
    Cellutech AB.
    Brumer, Harry
    The Michael Smith Laboratories and the Department of Chemistry, The University of British Columbia.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Adsorption of Xyloglucan onto Cellulose Surfaces of Different Morphologies: An Entropy-Driven Process2016In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 9, p. 2801-2811Article in journal (Refereed)
    Abstract [en]

    The temperature-dependence of xyloglucan (XG) adsorption onto smooth cellulose model films regenerated from N-methylmorpholine N-oxide (NMMO) was investigated using surface plasmon resonance spectroscopy, and it was found that the adsorbed amount increased with increasing temperature. This implies that the adsorption of XG to NMMO-regenerated cellulose is endothermic and supports the hypothesis that the adsorption of XG onto cellulose is an entropy-driven process. We suggest that XG adsorption is mainly driven by the release of water molecules from the highly hydrated cellulose surfaces and from the XG molecules, rather than through hydrogen bonding and van der Waals forces as previously suggested. To test this hypothesis, the adsorption of XG onto cellulose was studied using cellulose films with different morphologies prepared from cellulose nanocrystals (CNC), semicrystalline NMMO-regenerated cellulose, and amorphous cellulose regenerated from lithium chloride/dimethylacetamide. The total amount of high molecular weight xyloglucan (XGHMW) adsorbed was studied by quartz crystal microbalance and reflectometry measurements, and it was found that the adsorption was greatest on the amorphous cellulose followed by the CNC and NMMO-regenerated cellulose films. There was a significant correlation between the cellulose dry film thickness and the adsorbed XG amount, indicating that XG penetrated into the films. There was also a correlation between the swelling of the films and the adsorbed amounts and conformation of XG, which further strengthened the conclusion that the water content and the subsequent release of the water upon adsorption are important components of the adsorption process.

  • 21. Berg, I. C. H.
    et al.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Arnebrant, T.
    Lubricating properties of the initial salivary pellicle - an AFM Study2003In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 19, no 6, p. 365-369Article in journal (Refereed)
    Abstract [en]

    The role of saliva in the oral cavity is manifold; an important function is to serve as lubricant between hard (enamel) and soft (mucosal) tissues. Intraoral lubrication is of crucial importance in order to maintain functions such as deglutition, mastication and the faculty of speech. A large number of people suffer from impaired salivary functions, displaying symptoms such as 'dry mouth'. This results in a need for methods to assess the lubricating properties of both native saliva and potential artificial saliva formulations. Here, normal as well as lateral forces, acting between adsorbed salivary films, have been measured for the first time by means of colloidal probe atomic force microscopy (AFM). It was found that the presence of salivary pellicles between hard surfaces reduces the friction coefficient by a factor of 20. This reduction of friction is consistent with the long-range purely repulsive nature of the normal forces acting between the salivary films. The lubricating mechanism is presumably based on a full separation of the sliding surfaces by the salivary films. The friction between salivary films has been investigated at normal loads that cover the clinical jaw closing forces, and it can be concluded that the lubricating properties are maintained within this load interval. The present study indicates the usefulness of colloidal probe AFM, which offers a direct and quantitative measure of lubrication at a molecular level, in the study of biotribological phenomena. In particular, the results obtained here may have implications for the development of saliva substitutes.

  • 22. Bergquist, Helen
    et al.
    Rocha, Cristina S. J.
    Alvarez-Asencio, Ruben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Universitario de Cantoblanco, Spain.
    Nguyen, Chi-Hung
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Smith, C. I. Edvard
    Good, Liam
    Nielsen, Peter E.
    Zain, Rula
    Disruption of Higher Order DNA Structures in Friedreich's Ataxia (GAA)(n) Repeats by PNA or LNA Targeting2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 11, article id e0165788Article in journal (Refereed)
    Abstract [en]

    Expansion of (GAA)(n) repeats in the first intron of the Frataxin gene is associated with reduced mRNA and protein levels and the development of Friedreich's ataxia. (GAA)(n) expansions form non-canonical structures, including intramolecular triplex (H-DNA), and Rloops and are associated with epigenetic modifications. With the aim of interfering with higher order H-DNA (like) DNA structures within pathological (GAA)(n) expansions, we examined sequence-specific interaction of peptide nucleic acid (PNA) with (GAA)(n) repeats of different lengths (short: n= 9, medium: n= 75 or long: n= 115) by chemical probing of triple helical and single stranded regions. We found that a triplex structure (H-DNA) forms at GAA repeats of different lengths; however, single stranded regions were not detected within the medium size pathological repeat, suggesting the presence of a more complex structure. Furthermore, (GAA) 4-PNA binding of the repeat abolished all detectable triplex DNA structures, whereas (CTT) 5-PNA did not. We present evidence that (GAA) 4-PNA can invade the DNA at the repeat region by binding the DNA CTT strand, thereby preventing non-canonical-DNA formation, and that triplex invasion complexes by (CTT) 5-PNA form at the GAA repeats. Locked nucleic acid (LNA) oligonucleotides also inhibited triplex formation at GAA repeat expansions, and atomic force microscopy analysis showed significant relaxation of plasmid morphology in the presence of GAA-LNA. Thus, by inhibiting disease related higher order DNA structures in the Frataxin gene, such PNA and LNA oligomers may have potential for discovery of drugs aiming at recovering Frataxin expression.

  • 23. Bergquist, Helen
    et al.
    Rocha, Cristina S. J.
    Álvarez-Asencio, Rubén
    Nguyen, Colleen Ramsey
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Smith, C I Edvard
    Good, L.
    Nielsen, Peter Egil
    Zain, Rula
    Structure and Photoactivatable Probes for Nucleic Acids and Kinases2016In: Biochimie, Vol. 128, no 129, p. 133-137Article in journal (Refereed)
  • 24.
    Besharat, Zahra
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Alvarez-Asencio, Ruben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tian, H.
    Yu, S.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Gothelid, M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    In-situ evaluation of dye adsorption on TiO2 using QCM2017In: EPJ Photovoltaics, ISSN 2105-0716, Vol. 8, article id 80401Article in journal (Refereed)
    Abstract [en]

    We measured the adsorption characteristics of two organic dyes; triphenylamine-cyanoacrylic acid (TPA-C) and phenoxazine (MP13), on TiO2, directly in a solution based on quartz crystal microbalance (QCM). Monitoring the adsorbed amount as a function of dye concentration and during rinsing allows determination of the equilibrium constant and distinction between chemisorbed and physisorbed dye. The measured equilibrium constants are 0.8 mM(-1) for TPA-C and 2.4 mM(-1) for MP13. X-ray photoelectron spectroscopy was used to compare dried chemisorbed layers of TPA-C prepared in solution with TPA-C layers prepared via vacuum sublimation; the two preparation methods render similar spectra except a small contribution of water residues (OH) on the solution prepared samples. Quantitative Nanomechanical Mapping Atomic Force Microscopy (QNM-AFM) shows that physisorbed TPA-C layers are easily removed by scanning the tip across the surface. Although not obvious in height images, adhesion images clearly demonstrate removal of the dye.

  • 25.
    Besharat, Zahra
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ghadami Yazdi, Milad
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Johnson, Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark W.
    SP Technical Research Institute of Sweden, Sweden.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Grönbeck, Henrik
    Se-C Cleavage of Hexane Selenol at Steps on Au(111)2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 8, p. 2630-2636Article in journal (Refereed)
    Abstract [en]

    Selenols are considered as an alternative to thiols in self-assembled monolayers, but the Se-C bond is one limiting factor for their usefulness. In this study, we address the stability of the Se-C bond by a combined experimental and theoretical investigation of gas phase-deposited hexane selenol (CH3(CH2)(5)SeH) on Au(111) using photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory (DFT). Experimentally, we find that initial adsorption leaves atomic Se on the surface without any carbon left on the surface, whereas further adsorption generates a saturated selenolate layer. The Se 3d component from atomic Se appears at 0.85 eV lower binding energy than the selenolate-related component. DFT calculations show that the most stable structure of selenols on Au(111) is in the form of RSe-Au-SeR complexes adsorbed on the unreconstructed Au(111) surface. This is similar to thiols on Au(111). Calculated Se 3d core-level shifts between elemental Se and selenolate in this structure nicely reproduce the experimentally recorded shifts. Dissociation of RSeH and subsequent formation of RH are found to proceed with high barriers on defect-free Au(111) terraces, with the highest barrier for scissoring R-Se. However, at steps, these barriers are considerably lower, allowing for Se-C bond breaking and hexane desorption, leaving elemental Se at the surface. Hexane is the selenol to selenolate formed by replacing the Se-C bond with a H-C bond by using the hydrogen liberated from transformation.

  • 26.
    Besharat, Zahra
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Alvarez Asencio, Ruben.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Yu, Shun
    In-situ evaluation of dye adsorption on TiO2 using QCMManuscript (preprint) (Other academic)
  • 27.
    Besharat, Zahra
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ghadami Yazdi, Milad
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Se-C cleavage of hexane selenol at steps on Au(111)Manuscript (preprint) (Other academic)
  • 28.
    Besharat, Zahra
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Mixed monolayers of alkane thiols with polar terminal group on gold: Investigation of structure dependent surface properties2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 484, no 279, p. 279-290, article id j.jcis.2016.08.053Article in journal (Refereed)
    Abstract [en]

    Adsorption of thiols with cationic or anionic terminal group on gold has been studied from mixed solutions of 11-Amino-1-undecanethiol (AUT) and 3-Mercaptopropionic acid (MPA) using Quartz Crystal Microbalance with Dissipation (QCM-D), X-ray Photoelectron Spectroscopy (XPS), atomic force microscopy (AFM) and contact angles. The goal is to probe the nature of such layers, and the additivity or otherwise of the pH responsiveness, with a view to evaluate their suitability as smart materials. For each of the two pure (unmixed) cases, ordered molecular monolayers are formed with sulfur binding to gold and the alkane chain pointing out from the surface as expected. Adsorption from the thiol mixtures, however, leads to a more complex behaviour. The surface concentration of thiols from the mixtures, as determined by QCM-D, is considerably lower than for the pure cases and it reaches a minimum at a 3:1 MPA/AUT relative concentration in the solution. The XPS results confirm a reduction in adsorbed amount in mixtures with the lowest overall intensity for the 3:1 ratio. Monolayers formed from mixtures display a wettability which is much lower and less pH sensitive. Collectively these results confirm that for adsorption from mixed systems, the configuration is completely different. Complex formation in the mixed solutions leads to the adsorption of molecules parallel to the surface in an axially in-plane configuration. This parallel layer of thiols is mechanically relatively robust to nano-shaving based on AFM measurements. These results will have a significant impact on the design of biomimetic surface coatings particularly when mixtures of oppositely charged molecules are present on the surface, as is commonly the case in biological, proteinaceous surfaces (e.g. hair and skin).

  • 29. Bogdanovic, G.
    et al.
    Meurk, A.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Tip friction - torsional spring constant determination2000In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 19, no 4, p. 397-405Article in journal (Refereed)
    Abstract [en]

    A non-destructive technique is presented for verifying torsional spring constants used in lateral force microscopy. Various calibrations of the microscope are required and these are detailed. The technique produces reasonable values which tend to be larger than those predicted from considerations of the cantilever dimensions. The differences are discussed in terms of length corrections and particularly the uncertainty in the thickness of the cantilevers, which has an enormous effect on the values obtained through a priori calculations. Methods for inferring the thickness are discussed. Further, artefacts in conventional force measurements related to the experiments performed here are discussed.

  • 30. Bogdanovic, G.
    et al.
    Tiberg, F.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Sliding friction between cellulose and silica surfaces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 19, p. 5911-5916Article in journal (Refereed)
    Abstract [en]

    An atomic force microscope was used to measure kinetic friction forces between a colloidal cellulose sphere and different planar surfaces in air. The planar surfaces were bare silica, silica modified with a monolayer of alkyl ketene dimer (AKD), a common additive used for paper sizing, and silica with surface grafted terminal methyl groups. Friction was measured as a function of the effective load resulting from adhesive interactions between the cellulose sphere and the planar surface. Friction in the regime of low effective loads was shown to be a linear function of the load, and the friction coefficients determined from the slope of these curves were 0.26, 0.07, and 0.021 for the cellulose-silica, cellulose-AKD, and cellulose-methylated silica systems, respectively. The ratio between friction coefficients for the two first systems agrees well with that reported for paper in the presence and absence of AKD sizing agents, respectively. In the high effective load regime, deviations from linearity between measured friction and load were observed. This is an indication that we have single asperity contact, at least at high loads. These results were analyzed in terms of a contact mechanics transition equation, By making assumptions on the moduli of the materials, the interfacial shear strength tau and the contact radius ao were calculated. The results obtained through this analysis provide an important insight into the relationship between friction and chemical surface properties.

  • 31. Boschkova, K.
    et al.
    Kronberg, B.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Imae, T.
    Study of thin surfactant films under shear using the tribological surface force apparatus2001In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, no 12, p. 815-822Article in journal (Refereed)
    Abstract [en]

    Static and dynamic behaviour of thin surfactant films in aqueous solution of hexadecyltrimethylammonium salicylate (C16TASal) were investigated using the tribological surface force apparatus. Normal force measurements show that 0.15 mM C16TASal builds up an innermost film of approximately 8-11 Angstrom thickness at each mica surface, indicating that the surfactant adsorbs in a flat conformation. Furthermore, the height of the force barrier at approximately 60 Angstrom is low (ca 2 mN/m) indicating that the second adsorbed layer is easily pushed out. Addition of salicylate salt to 0.15 mM C16TASal give rise to a more close packed structure, with a total thickness of 62-65 Angstrom. indicative of a micellar or bilayer arrangement at the surfaces. Furthermore, the frequency dependence of the shear modulus was investigated both at close separation at the innermost force barrier and at larger separations (up to 300-400 Angstrom). The visco-elastic measurements show that the elasticity modulus, G ', dominates over the loss modulus, G , for all studied cases, indicative of a more solid-like than liquid-like film. Finally, it is shown that shear at high contact pressures induces new aggregate structures at the surface.

  • 32. Boshkova, Katrin
    et al.
    Kronberg, Bengt
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Imae, Toyoko
    Visco-elastic properties of thin surfactant films studied with the tribological surface force apparatus.2000Conference paper (Refereed)
  • 33.
    Brumer, Harry
    et al.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sinnott, M. L.
    Teeri, Tuula T.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience.
    Cross-Linking Involving a Polymeric Carbohydrate Material2005Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention relates to a method of cross-linking a polymeric carbohydrate material with a second material by means of a soluble carbohydrate polymer and a crosslinking agent. The present invention furthermore relates to the resulting cross-linked material, to uses of the cross-linked material, as well as to a kit comprising the soluble carbohydrate polymer and the cross-linking agent.

  • 34. Brumer, Harry
    et al.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Sinnot, Michael
    Teeri, Tuula
    Zhou, Qi
    Crosslinking involving a polymeric carbohydrate material2006Patent (Other (popular science, discussion, etc.))
  • 35. Cardenas, Marite
    et al.
    Valle-Delgado, Juan Jose
    Hamit, Jildiz
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Arnebrant, Thomas
    Interactions of hydroxyapatite surfaces: Conditioning films of human whole saliva2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 14, p. 7262-7268Article in journal (Refereed)
    Abstract [en]

    Hydroxyapatite is a very interesting material given that it is the main component in tooth enamel and because of its uses in bone implant applications. Therefore, not only the characterization of its surface is of high relevance but also designing reliable methods to study the interfacial properties of films adsorbed onto it. In this paper we apply the colloidal probe atomic force microscopy method to investigate the surface properties of commercially available hydroxyapatite surfaces (both microscopic particles and macroscopic discs) in terms of interfacial and frictional forces. In this way, we find that hydroxyapatite surfaces at physiological relevant conditions are slightly negatively charged. The surfaces were then exposed to human whole saliva, and the surface properties were re-evaluated. A thick film was formed that was very resistant to mechanical stress. The frictional measurements demonstrated that the film was indeed highly lubricating, supporting the argument that this system may prove to be a relevant model for evaluating dental and implant systems.

  • 36.
    Claesson , Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Measuring Interactions between Surfaces2001In: Handbook of Applied Surface and Colloid Chemistry, John Wiley and Sons , 2001Chapter in book (Refereed)
  • 37. Cooper, P. K.
    et al.
    Li, H.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Webber, G. B.
    Atkin, R.
    Tribotronic control of friction in oil-based lubricants with ionic liquid additives2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 34, p. 23657-23662Article in journal (Refereed)
    Abstract [en]

    Atomic force microscopy (AFM) reveals that tribotronic control of friction using an external potential applied to a gold surface is possible for ionic liquid (IL) concentrations as low as 5 mol% in hexadecane. The IL used is trihexyl(tetradecyl) phosphonium bis(2,4,4-trimethylpentyl)phosphinate, in which both the cation and anion have surfactant-like structures, and is miscible with hexadecane in all proportions. For IL concentrations less than 5 mol% friction does not vary with applied potential, but for 5 mol% and above changing the potential changes the composition of the IL boundary layer from cation-enriched (negative potentials) to anion-enriched (positive potentials). As the lubricities of the cation-rich and anion-rich boundary layers differ, this enables active control of friction in oil-based lubricants.

  • 38.
    Cranston, Emily D.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Gray, Derek G.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Direct Surface Force Measurements of Polyelectrolyte Multi layer Films Containing Nanocrystalline Cellulose2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 22, p. 17190-17197Article in journal (Refereed)
    Abstract [en]

    Polyelectrolyte multilayer films containing nanocrystalline cellulose (NCC) and poly(allylamine hydrochloride) (PAH) make up a new class of nanostructured composite with applications ranging from coatings to biomedical devices. Moreover, these materials arc amenable to surface force studies using colloid-probe atomic force microscopy (CP-AFM). For electrostatically assembled films with either NCC or PAH as the outermost layer, surface morphology was investigated by A FM and wettability was examined by contact angle measurements. By varying the surrounding ionic strength and pH, the relative contributions from electrostatic, van der Waals, steric. and polymer bridging interactions were evaluated. The ionic cross-linking in these films rendered them stable under all solution conditions studied although swelling at low pH and high ionic strength was inferred. The underlying polymer layer in the multilayered film was found to dictate the dominant surface forces when polymer migration and chain extension were facilitated. The precontact normal forces between a silica probe and an NCC-capped multilayer film were monotonically repulsive at pH values where the material surfaces were similarly and fully charged. In contrast, at pH 3.5, the anionic surfaces were weakly charged but the underlying layer of cationic PAH was fully charged and attractive forces dominated due to polymer bridging from extended PAH chains. The interaction with an anionic carboxylic acid probe showed similar behavior to the silica probe; however, for a cationic amine probe with an anionic NCC-capped Film, electrostatic double-layer attraction at low pH, and electrostatic double-layer repulsion at high pH, Were observed. Finally, the effect or the capping layer was studied with an anionic probe, which indicated that NCC-capped films exhibited purely repulsive forces which were larger in magnitude than the combination of electrostatic double-layer attraction and steric repulsion. measured for PAH-capped films. Wherever possible, DLVO theory was used to fit the measured surface forces and apparent surface potentials and surface charge densities were calculated.

  • 39.
    Cranston, Emily D.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Gray, Derek
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Interfacial properties of nanocrystalline cellulose composites prepared through layer-by-layer assembly2011In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 241Article in journal (Other academic)
  • 40.
    Cranston, Emily
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Werzer, Oliver
    Alvarez, Ruben
    Atkin, R
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Nanotribology of protic ionic liquids: Green lubricants for micro-/nano-electromechanical devices2011In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 241Article in journal (Other academic)
  • 41. Elbourne, Aaron
    et al.
    Sweeney, James
    Webber, Grant B.
    Wanless, Erica J.
    Warr, Gregory G.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Atkin, Rob
    Adsorbed and near-surface structure of ionic liquids determines nanoscale friction2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 60, p. 6797-6799Article in journal (Refereed)
    Abstract [en]

    Surface-adsorbed and near-surface ion layer structure controls nanotribology in the silica-propylammonium nitrate (PAN)-mica system. Atomic Force Microscopy (AFM) imaging and normal force curves reveal that the normal load dictates the number of interfacial ion layers and the lateral layer structure. Shear force measurements show the lubricity of the interface changes with the number, and lateral structure, of the confined ion layer(s).

  • 42. Feiler, A. A.
    et al.
    Jenkins, P.
    Rutland, Mark W
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of relative humidity on adhesion and frictional properties of micro- and nano-scopic contacts2005In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 19, no 05-mar, p. 165-179Article in journal (Refereed)
    Abstract [en]

    The effect of relative humidity (RH) oil the interactions of AFM tips and colloidal probes with hydrophilic silica substrates is investigated. Both friction and adhesion are studied. For the case of a colloidal probe the interaction is characteristic of a multiasperity contact, the adhesion increased with increasing RH and above a certain threshold relative humidity a large increase in adhesion was measured. This behaviour is explained in terms of a recent model where the Kelvin radius of the condensate becomes larger than some characteristic roughness on the surface. The interaction between the tip and the substrate also exhibited an increase in adhesion above a threshold RH although the increase was much less marked than with the colloid probe. The friction decreased with increasing humidity for both tip and colloid probe although the friction force was much less sensitive than adhesion to changes in RH. Stick-slip behaviour was observed between tip and substrate for all humidities at high loads, but only at the lowest RH (about 5%) it was observed at all loads. At higher humidity the behaviour became increasingly continuum on the experimental timescale, presumably due to viscous contributions from the water. Stick-slip was not observed for the colloidal probe friction measurements.

  • 43. Feiler, A.
    et al.
    Plunkett, M. A.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Atomic force microscopy measurements of adsorbed polyelectrolyte layers. 1. Dynamics of forces and friction2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, no 10, p. 4173-4179Article in journal (Refereed)
    Abstract [en]

    The measurement of surface forces and friction between silica substrates bearing adsorbed layers acrylamide-1% [3-(2-methylpropionamide)propyl]trimethyl ammonium chloride (AM-MAPTAC) was examined using atomic force microscopy. The cationic polymer had a large molecular weight (900 000) and a very low charge density (1% MAPTAC units). The force curves in the presence of adsorbed polyelectrolyte showed a very long range repulsive interaction and large deformation on compression typical of electrosteric interactions and consistent with the expected adsorption profile. There was also a strong dependence on the scan rate with increased repulsion during approach and increased attraction during separation as the scan rate increased. The hysteresis was attributed entirely to a hydrodynamic interaction induced by the polyelectrolyte. At slow enough scan rates, the hysteresis between approach and retract curves was absent. The friction force measurements were sensitive to both applied load and scan rate. With increasing applied load, a critical load was apparent, above which the friction force increased. Upon decrease of the load, the friction force remained higher than that before the yield point, suggesting a metastable deformation of the polymer layer. In addition, the friction coefficient increased with increasing scan rate. At low scan rates the friction coefficient was lower than the bare surfaces, whereas at high scan rates the friction coefficient was significantly larger that obtained than for the bare surfaces. Subsequent force curves taken after friction measurements confirm that a permanent change in the polyelectrolyte layer had occurred. The magnitude of the repulsive interaction was reduced to about half of its original force.

  • 44. Feiler, Adam A.
    et al.
    Bergstrom, Lennart
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Superlubricity using repulsive van der Waals forces2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 6, p. 2274-2276Article in journal (Refereed)
    Abstract [en]

    Using colloid probe atomic force microscopy, we show that if repulsive van der Waals forces exist between two surfaces prior to their contact then friction is essentially precluded and supersliding is achieved. The friction measurements presented here are of the same order as the lowest ever recorded friction coefficients in liquid, though they are achieved by a completely different approach. A gold sphere attached to an AFM cantilever is forced to interact with a smooth Teflon surface (templated on mica). In cyclohexane, a repulsive van der Waals force is observed that diverges at short separations. The friction coefficient associated with this system is on the order of 0.0003. When the refractive index of the liquid is changed, the force can be tuned from repulsive to attractive and adhesive. The friction coefficient increases as the Hamaker constant becomes more positive and the divergent repulsive force, which prevents solid-solid contact, gets switched off.

  • 45.
    Feiler, Adam A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Jenkins, Paul
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of relative humidity on adhesion and frictional properties of micro- and nano-scopic contacts2005In: Atomic Force Microscopy in Adhesion Studies, Leiden-Boston: VSP , 2005, p. 491-505Chapter in book (Refereed)
  • 46.
    Feiler, Adam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Stiernstedt, Johanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Theander, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Jenkins, Paul
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of capillary condensation on friction force and adhesion2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 2, p. 517-522Article in journal (Refereed)
    Abstract [en]

    Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobized) after long (24 h) exposure to high-humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction - load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate, with the hydrophobized silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.

  • 47. Filippov, Andrei
    et al.
    Gnezdilov, Oleg I.
    Hjalmarsson, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Antzutkin, Oleg N.
    Glavatskih, Sergei
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Acceleration of diffusion in ethylammonium nitrate ionic liquid confined between parallel glass plates2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 38, p. 25853-25858Article in journal (Refereed)
  • 48. Gebbie, Matthew A.
    et al.
    Smith, Alexander M.
    Dobbs, Howard A.
    Lee, Alpha A.
    Warr, Gregory G.
    Banquy, Xavier
    Valtiner, Markus
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Israelachvili, Jacob N.
    Perkin, Susan
    Atkin, Rob
    Long range electrostatic forces in ionic liquids2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 7, p. 1214-1224Article in journal (Refereed)
    Abstract [en]

    Ionic liquids are pure salts that are liquid under ambient conditions. As liquids composed solely of ions, the scientific consensus has been that ionic liquids have exceedingly high ionic strengths and thus very short Debye screening lengths. However, several recent experiments from laboratories around the world have reported data for the approach of two surfaces separated by ionic liquids which revealed remarkable long range forces that appear to be electrostatic in origin. Evidence has accumulated demonstrating long range surface forces for several different combinations of ionic liquids and electrically charged surfaces, as well as for concentrated mixtures of inorganic salts in solvent. The original interpretation of these forces, that ionic liquids could be envisioned as "dilute electrolytes,'' was controversial, and the origin of long range forces in ionic liquids remains the subject of discussion. Here we seek to collate and examine the evidence for long range surface forces in ionic liquids, identify key outstanding questions, and explore possible mechanisms underlying the origin of these long range forces. Long range surface forces in ionic liquids and other highly concentrated electrolytes hold diverse implications from designing ionic liquids for energy storage applications to rationalizing electrostatic correlations in biological self-assembly.

  • 49.
    Ghalgaoui, Ahmed
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Shimizu, Ryosuke
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hosseinpour, Saman
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Alvarez-Asencio, Rubén
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    McKee, Clayton
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Monolayer Study by VSFS: In Situ Response to Compression and Shear in a Contact2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 11, p. 3075-3085Article in journal (Refereed)
    Abstract [en]

    Self-assembled octadecyltrichlorosilane ((OTS), CH3(CH2)(17)SiCl3) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared. The monolayers were characterized with atomic force microscopy (AFM) and contact angle measurements; their conformation was studied before, during, and after contact with a polymer (either PDMS or PTFE) surface using the vibrational sum frequency spectroscopy (VSFS) technique. During contact, the effect of pressure was studied for both polymer surfaces, but in the case of PTFE, the effect of shear rate on the contact was simultaneously studied. The VSFS response of the monolayers with pressure was almost entirely due to changes in the real area of contact with the polymer and therefore the Fresnel factors, whereas sliding caused disorder in the previously all-trans monolayer, as evidenced by a significant increase in the population of gauche defects.

  • 50. Hansson, Petra M.
    et al.
    Skedung, Lisa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Robust Hydrophobic Surfaces Displaying Different Surface Roughness Scales While Maintaining the Same Wettability2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 13, p. 8153-8159Article in journal (Refereed)
    Abstract [en]

    A range of surfaces coated with spherical silica particles, covering the size range from nanometer to micrometer, have been produced using Langmuir-Blodgett (LB) deposition. The particles were characterized both in suspension and in the Langmuir trough to optimize the surface preparation procedure. By limiting the particle aggregation and surface layer failures during the preparation steps, well-defined monolayers with a close-packed structure have been obtained for all particle sizes. Thus, this procedure led to structured surfaces with a characteristic variation in the amplitude and spatial roughness parameters. In order to obtain robust surfaces, a sintering protocol and an AFM-based wear test to determine the stability of the deposited surface layer were employed. Hydrophobization of the LB films followed by water contact angle measurements showed, for all tested particle sizes, the same increase in contact angle compared to the contact angle of a flat hydrophobic surface. This indicates nearly hexagonal packing and gives evidence for nearly, complete surface wetting of the surface features.

1234 1 - 50 of 188
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