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  • 1.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Potential of a new low-friction coating based on inorganic fullerens: comparison with state-of-the-art PVD coatings2009Conference paper (Refereed)
  • 2.
    Ballo, Ahmed
    et al.
    Gothenburg University.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lindahl, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Emanuelsson, Lena
    Gothenburg University.
    Palmqvist, Anders
    Gothenburg University.
    Lausmaa, Jukka
    SP.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Thomsen, Peter
    Gothenburg University.
    Early bone tissue responses to a slicon-substituted apatite/titanium dioxide coating on titanium implant2010Conference paper (Refereed)
  • 3.
    Ballo, Ahmed
    et al.
    Gothenburg University.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lindahl, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lausmaa, Jukka
    SP.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Thomsen, Peter
    Gothenburg University.
    Bone responses to ions-substituted apatite/titanium dioxide coating on titanium implants2010Conference paper (Refereed)
  • 4.
    Berger, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, U
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Eriksson, M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, H
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, S
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The multilayer effect in abrasion: optimising the combination of hard and tough phases1999In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 116-119, p. 1138-1144Article in journal (Other academic)
    Abstract [en]

    In the present investigation it is shown that the wear resistance of multilayer PVD coatings, combining relatively soft but tough chromium (Cr) and harder but more brittle chromium nitride (CrN): exceeds that of both its phases. This striking exception to

  • 5.
    Bou-Francis, Antony
    et al.
    School of Mechanical Engineering, University of Leeds, UK.
    Lopez, Alejandro
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hall, Richard M.
    School of Mechanical Engineering, University of Leeds, UK.
    Kapur, Nikil
    School of Mechanical Engineering, University of Leeds, UK.
    Assessing cement injection behaviour in cancellous bone: An in vitro study using flow models2014In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 29, no 4, p. 582-594Article in journal (Refereed)
    Abstract [en]

    Understanding the cement injection behaviour during vertebroplasty and accurately predicting the cement placement within the vertebral body is extremely challenging. As there is no standardized methodology, we propose a novel method using reproducible and pathologically representative flow models to study the influence of cement properties on injection behaviour. The models, confined between an upper glass window and a lower aluminium plate, were filled with bone marrow substitute and then injected (4, 6 and 8min after cement mixing) with commercially available bone cements (SimplexP, Opacity+, OsteopalV and Parallax) at a constant flow rate (3mL/min). A load cell was used to measure the force applied on the syringe plunger and calculate the peak pressure. A camera was used to monitor the cement flow during injection and calculate the following parameters when the cement had reached the boundary of the models: the time to reach the boundary, the filled area and the roundness. The peak pressure was comparable to that reported during clinical vertebroplasty and showed a similar increase with injection time. The study highlighted the influence of cement formulations and model structure on the injection behaviour and showed that cements with similar composition/particle size had similar flow behaviour, while the introduction of defects reduced the time to reach the boundary, the filled area and the roundness. The proposed method provides a novel tool for quick, robust differentiation between various cement formulations through the visualization and quantitative analysis of the cement spreading at various time intervals.

  • 6.
    Brohede, Ulrika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Forsgren, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Roos, Stefan
    Mihranyan, Albert
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Multifunctional implant coatings providing possibilities for fast antibiotics loading with subsequent slow release2009In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 20, no 9, p. 1859-1867Article in journal (Refereed)
    Abstract [en]

    The possibility to fast-load biomimetic hydroxyapatite coatings on surgical implant with the antibiotics Amoxicillin, Gentamicin sulfate, Tobramycin and Cephalothin has been investigated in order to develop a multifunctional implant device offering sustained local anti-bacterial treatment and giving the surgeon the possibility to choose which antibiotics to incorporate in the implant at the site of surgery. Physical vapor deposition was used to coat titanium surfaces with an adhesion enhancing gradient layer of titanium oxide having an amorphous oxygen poor composition at the interface and a crystalline bioactive anatase TiO2 composition at the surface. Hydroxyapatite (HA) was biomimetically grown on the bioactive TiO2 to serve as a combined bone in-growth promoter and drug delivery vehicle. The coating was characterized using scanning and transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The antibiotics were loaded into the HA coatings via soaking and the subsequent release and antibacterial effect were analyzed using UV spectroscopy and examination of inhibition zones in a Staphylococcus aureus containing agar. It was found that a short drug loading time of 15 min ensured antibacterial effects after 24 h for all antibiotics under study. It was further found that the release processes of Cephalothin and Amoxicillin consisted of an initial rapid drug release that varied unpredictably in amount followed by a reproducible and sustained release process with a release rate independent of the drug loading times under study. Thus, implants that have been fast-loaded with drugs could be stored for ~10 min in a simulated body fluid after loading to ensure reproducibility in the subsequent release process. Calculated release rates and measurements of drug amounts remaining in the samples after 22 h of release indicated that a therapeutically relevant dose could be achieved close to the implant surface for about 2 days. Concluding, the present study provides an outline for the development of a fast-loading slow-release surgical implant kit where the implant and the drug are separated when delivered to the surgeon, thus constituting a flexible solution for the surgeon by offering the choice of quick addition of antibiotics to the implant coating based on the patient need.

  • 7.
    Brohede, Ulrika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Zhao, Shuxi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lindberg, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Mihranyan, Albert
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Forsgren, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A novel graded bioactive high adhesion implant coating2009In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 255, no 17, p. 7723-7728Article in journal (Refereed)
    Abstract [en]

     One method to increase the clinical success rate of metal implants is to increase their bone bonding properties, i.e. to develop a bone   bioactive surface leading to reduced risks of interfacial problems.   Much research has been devoted to modifying the surface of metals to   make them become bioactive. Many of the proposed methods include   depositing a coating on the implant. However, there is a risk of coating failure due to low substrate adhesion. This paper describes a method to obtain bioactivity combined with a high coating adhesion via   a gradient structure of the coating. Gradient coatings were deposited   on Ti (grade 5) using reactive magnetron sputtering with increasing   oxygen content. To increase the grain size in the coating, all coatings   were post annealed at 385 degrees C. The obtained coating exhibited a gradual transition over 70 nm from crystalline titanium oxide (anatase)  at the surface to metallic Ti in the substrate, as shown using  cross-section transmission electron microscopy and X-ray photoelectron   spectroscopy depth pro. ling. Using scratch testing, it could be shown that the adhesion to the substrate was well above 1 GPa. The bioactivity of the coating was verified in vitro by the spontaneous   formation of hydroxylapatite upon storage in phosphate buffer solution at 37 degrees C for one week.   The described process can be applied to implants irrespective of bulk  metal in the base and should introduce the possibility to create safer permanent implants like reconstructive devices, dental, or spinal implants.

  • 8.
    Broqvist, Natalia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gunnarsson, S.
    Properties affecting machinability of hot work tool steels2009In: Tool Steels - Deciding Factor in Worldwide Production: Tool 09; Proceedings of the 8th International Tooling Conference, RWTH Aachen University, Aachen, Germany, June 2 - 4, 2009 / [ed] P. Beiss, Christoph Broeckmann, Mainz, 2009Conference paper (Refereed)
  • 9.
    Broqvist, Natalia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gunnarsson, S.
    Björk, T.
    Riddar, Frida
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On the relation between composition, oxidation and machinability of tool steels2008Conference paper (Refereed)
  • 10.
    Broqvist, Natalia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gunnarsson, S.
    Coronel, E.
    Machinability of modern hot work tool steels2006In: Proceedings of the 7th Int. Tooling Conference, Torino, Italy, 2006, 2006Conference paper (Refereed)
  • 11.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Development and evaluations of self-setting bioceramics microneedles2014Conference paper (Refereed)
  • 12.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Li, Hao
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Otolaryngology and Head and Neck Surgery.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bioceramic microneedles with flexible and self-swelling substrate2015In: European journal of pharmaceutics and biopharmaceutics, ISSN 0939-6411, E-ISSN 1873-3441, Vol. 94, p. 404-410Article in journal (Refereed)
    Abstract [en]

    To reduce the effort required to penetrate the skin and optimize drug release profiles, bioceramic microneedle arrays with higher-aspect-ratio needles and a flexible and self-swelling substrate have been developed. Swelling of the substrate can assist in separating it from the needles and leave them in the skin as a drug depot. The preparation procedures for this bioceramic microneedle are described in the paper. Clonidine hydrochloride, the model drug, was released in a controlled manner by the microneedle device in vitro. Results showed that the microneedle array with a flexible and self-swelling substrate released the drug content faster than the array with a rigid substrate. Disintegration of the needle material and diffusion of the drug molecules are believed as the main control mechanisms of the drug release from these microneedle arrays. Ex vivo skin penetration showed that they can effectively penetrate the stratum corneum without an extra device. This work represents a progression in the improvement of bioceramic microneedles for transdermal drug delivery.

  • 13.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bioceramic microneedles with flexible and self-swelling substrateArticle in journal (Other academic)
  • 14.
    Cai, Yanling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Melhus, Åsa
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Bacteriology.
    A novel dental adhesive with bioactive and on-demand biofilm eliminating properties2010Conference paper (Refereed)
  • 15.
    Cardemil, Carina
    et al.
    University of Gothenburg.
    Elgali, Ibrahim
    University of Gothenburg.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Emanuelsson, Lena
    Gothenburg University.
    Norlindh, Birgitta
    University of Gothenburg.
    Omar, Omar
    University of Gothenburg.
    Thomsen, Peter
    Gothenburg University.
    Strontium-Doped Calcium Phosphate and Hydroxyapatite Granules Promote Different Inflammatory and Bone Remodelling Responses in Normal and Ovariectomised Rats2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 12, p. e84932-Article in journal (Refereed)
    Abstract [en]

    The healing of bone defects may be hindered by systemic conditions such as osteoporosis. Calcium phosphates, with or without ion substitutions, may provide advantages for bone augmentation. However, the mechanism of bone formation with these materials is unclear. The aim of this study was to evaluate the healing process in bone defects implanted with hydroxyapatite (HA) or strontium-doped calcium phosphate (SCP) granules, in non-ovariectomised (non-OVX) and ovariectomised (OVX) rats. After 0 (baseline), six and 28d, bone samples were harvested for gene expression analysis, histology and histomorphometry. Tumour necrosis factor-alpha (TNF-alpha), at six days, was higher in the HA, in non-OVX and OVX, whereas interleukin-6 (IL-6), at six and 28d, was higher in SCP, but only in non-OVX. Both materials produced a similar expression of the receptor activator of nuclear factor kappa-B ligand (RANKL). Higher expression of osteoclastic markers, calcitonin receptor (CR) and cathepsin K (CatK), were detected in the HA group, irrespective of non-OVX or OVX. The overall bone formation was comparable between HA and SCP, but with topological differences. The bone area was higher in the defect centre of the HA group, mainly in the OVX, and in the defect periphery of the SCP group, in both non-OVX and OVX. It is concluded that HA and SCP granules result in comparable bone formation in trabecular bone defects. As judged by gene expression and histological analyses, the two materials induced different inflammatory and bone remodelling responses. The modulatory effects are associated with differences in the spatial distribution of the newly formed bone.

  • 16.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Grandfield, Kathryn
    McMaster University.
    Yu, Shun
    KTH.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Synthesis of calcium phosphate crystals with thin nacreous structure2016In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 18, no 6, p. 1064-1069Article in journal (Refereed)
    Abstract [en]

    Nacre-like structures have attracted great interest in recent years due to their outstanding toughness, stiffness and impact resistance. However, there is a challenge associated with engineering nacre-like calcium phosphate crystals. In this study, thin nacreous-like monetite sheets were synthesized in solutions guided by a surfactant. The influence of temperature, initial pH, Ca/P ratio, stirring time and the concentration of cetyltrimethylammonium bromide (CTAB) on the nacre-like structure has been studied. Findings showed that a nacre-like structure could only be formed at a high temperature (90 degrees C), high initial pH (11), sufficient stirring time (3 h), and under the presence of CTAB. A small-angle X-ray scattering experiment carried out at a synchrotron radiation facility showed that the distance between nanolayers was around 2.6 nm and TEM confirmed the fine sheet-like structure. The mechanism of the formation the nacre-like structure and its characterization were discussed.

  • 17.
    Coronel, E
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Olsson, E
    The effect of carbon content on the microstructure of hydrogen-free physical vapour deposited titanium carbide films2009In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 1, p. 71-76Article in journal (Refereed)
    Abstract [en]

    Titanium carbide (TiC) coatings for tribological applications were deposited on high speed steel. Several coatings with different titanium to carbon ratio were deposited by means of physical vapour deposition in which titanium was evaporated and carbon was sputtered. The coatings were characterised using analytical electron microscopy. It was observed that the change in titanium to carbon ratio significantly changed the microstructure of the coatings. The low carbon containing coatings consisted of columnar grains exhibiting a preferred crystallographic orientation whereas the coating with highest carbon content consisted of randomly ordered TiC grains in an amorphous carbon matrix. Energy filtered transmission electron microscopy revealed a change in Ti/C ratio as the distance from the substrate increased. The titanium to carbon ratio was observed to increase with distance from the substrate until a stable level was reached. This is due to a variation in the titanium evaporation during the early stages of film growth. This change of the titanium to carbon ratio affected the columnar growth in the initial stage of coating growth for the coatings with low carbon content.

  • 18.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Electron Microscopy and Nanoengineering.
    FIB - verktyg för verktygsanalys2006Conference paper (Other (popular science, discussion, etc.))
  • 19.
    Coronel, Ernesto
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Elektronmikroskopi och Nanoteknologi.
    Hanson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materialvetenskap.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Elektronmikroskopi och Nanoteknologi.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materialvetenskap.
    Mechanisms of Work Material Adhesion in Tooling Operations Revealed by TEM2006Conference paper (Other academic)
  • 20. Coutinho, E.
    et al.
    Jarmar, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Neves, AA
    Verlinden, B.
    Van Meerbeek, B.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams2009In: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 25, no 11, p. 1325-1337Article in journal (Refereed)
    Abstract [en]

     Current available techniques for transmission electron microscopy (TEM)   of tooth biomaterial interfaces are mostly ineffective for brittle   phases and impair integrated chemical and morphological   characterization.   Objectives. The aims of this study were (1) to determine the   applicability of new focused ion beam (FIB) and broad ion beam (BIB)   techniques for TEM preparation of tooth-biomaterial interfaces; (2) to   characterize the interfacial interaction with enamel and dentin of a   conventional glass-ionomer (Chem. l Superior, DeTrey Dentsply,   Germany), a 2-step self-etch (Clear. l SE, Kuraray, Japan) and a 3-step   etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to   characterize clinically relevant interfaces obtained from actual   Class-I cavities.   Methods. After bonding to freshly extracted human third molars,   non-demineralized and non-stained sections were obtained using the   FIB/BIB techniques and examined under TEM.   Results. The main structures generally disclosed in conventional   ultramicrotomy samples were recognized in FIB/BIB-based ones. There   were not any major differences between FIB and BIB concerning the   resulting ultrastructural morphology. FIB/BIB-sections enabled to   clearly resolve sub-micron hydroxyapatite crystals on top of hard   tissues and the interface between matrix and filler in all materials,   even at nano-scale. Some investigated interfaces disclosed areas with a   distinct "fog" or "melted look", which is probably an artifact due to   surface damage caused by the high-energy beam. Interfaces with enamel   clearly disclosed the distinct "keyhole" shape of enamel rods sectioned   at 90 degrees, delimited by a thin electron-lucent layer of inter-rod   enamel. At regions where enamel crystals ran parallel with the   interface, we observed a lack of interaction and some de-bonding along   with interfacial void formation.   Significance. The FIB/BIB methods are viable and reliable alternatives   to conventional ultramicrotomy for preparation of thin sections of   brittle and thus difficult to cut biomaterial-hard tissue interfaces.   They disclose additional ultrastructural information about both   substrates and are more suitable for advanced analytic procedures.

  • 21.
    Crossley, A
    et al.
    AEA Technology, UK.
    Johnston, C
    Hutchings, I M
    Myhra, S
    Temple, J A G
    Wiklund, U
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Surface treatment for galling protection of titanium alloys: characterization by surface-specific electron and Raman spectroscopies2002In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 414, no 2, p. 224-230Article in journal (Refereed)
  • 22.
    Díez-Escudero, Anna
    et al.
    Technical University of Catalonia, Spain & Barcelona Research Center of Multiscale Science and Engineering, Spain.
    Montserrat, Espanol
    Technical University of Catalonia, Spain & Barcelona Research Center of Multiscale Science and Engineering, Spain.
    Di Pompo, Gemma
    Istituto Ortopedico Rizzoli, Italy.
    Torregianni, Elena
    Istituto Ortopedico Rizzoli, Italy.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ciapetti, Gabriela
    Istituto Ortopedico Rizzoli, Italy.
    Baldini, Nicola
    Istituto Ortopedico Rizzoli, Italy.
    Ginebra, Maria-Pau
    Technical University of Catalonia, Spain & Barcelona Research Center of Multiscale Science and Engineering, Spain.
    Heparinisation as a tool to modulate osteoclastogenesis on calcium phosphates2017Conference paper (Refereed)
  • 23.
    Edqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Applications of active materials2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Energy efficiency is a vital key component when designing and miniaturizing self sustained microsystems. The smaller the system, the smaller is the possibility to store enough stored energy for a long and continuous operational time. To move such a system in an energy efficient way, a piezoelectrical locomotion module consisting of four resonating cantilevers has been designed, manufactured and evaluated in this work. The combination of a suitable substrate, a multilayered piezoelectric material to reduce the voltage, and a resonating drive mechanism resulted in a low power demand.

    A manufacturing process for multilayer cantilever actuators made of P(VDF-TrFE) with aluminum electrodes on a substrate of flexible printed circuit board (FPC), has been developed. An important step in this process was the development of an etch recipe for dry etching the multilayer actuators in an inductive plasma equipment.

    Formulas for the quasi static tip deflection and resonance frequency of a multilayered cantilever, have been derived. Through theses, it was found that the multilayered structures should be deposited on the polymer side of the FPC in order to maximize the tip deflection.

    Both a large and a miniaturized locomotion module were manufactured and connected by wires to verify that the three legged motion principal worked to move the structures forward and backward, and turn it right and left. By touching and adding load, to a fourth miniaturized cantilever, its ability to act as a contact sensor and carry object was verified.

    The presented locomotion module is part of a multifunctional microsystem, intended to be energy efficient and powered by a solar panel with a total volume of less than 25 mm3 and weight 65 mg. The whole system, consisting of a solar cell, an infra red communication module, an integrated circuit for control, three capacitors for power regulating, the locomotion module and an FPC connecting the different modules, was surface mounted using a state of the art industrial facility. Two fully assembled systems could be programmed both through a test connector and through optical sensors in the multifunctional solar cell. One of these was folded together to the final configuration of a robot. However, the entire system could not be tested under full autonomous operating conditions. On the other hand, using wires, the locomotion module could be operated and used to move the entire system from a peak-to-peak voltage of 3.0 V.

    List of papers
    1. Monolithic fabrication of multilayer P(VDF-TrFE) cantilevers
    Open this publication in new window or tab >>Monolithic fabrication of multilayer P(VDF-TrFE) cantilevers
    2008 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 144, no 2, p. 314-320Article in journal (Refereed) Published
    Abstract [en]

    When operating a piezoelectric actuator the use of multilayers has for a long time proven to be a good solution to maintain a high electric field at a reduced applied voltage. The piezoelectric copolymer polyvinylidene-trifluoroethylene P(VDF-TrFE) has rather low piezoelectric constant compared to piezoceramics but it can withstand much higher electric fields. As the copolymer can be spin coated the individual layer thickness of the multilayer can easily be reduced to a few m and rather large strains can be achieved at a moderate voltage. Here a monolithic fabrication technique for producing P(VDF-TrFE) actuators, without any lamination or adhesive layers, is presented. To fabricate the multilayer successive spin coating of the piezoelectric polymer polyvinylidene-trifluoroethylene P(VDF-TrFE) and electrode evaporation on a substrate was performed. Four different substrate materials were coated with a multilayer stack of 6 active P(VDF-TrFE) layers and 7 aluminum electrodes. The monolithic multilayer structures with patterned electrodes were diced by a cutting saw to produce unimorph cantilevers. No delamination or dissolution could be observed between adjacent copolymer layers. The cantilevers were evaluated in terms of static and resonant deflection and the Q-factor was estimated from the frequency spectra. A discussion regarding the influence of the Q-factor on the fabrication process tolerance is given. The different substrate materials used was stainless steel, flexible printed circuit board (FPC), polycarbonate and aluminum. The Q-factor varied from 30 for the polycarbonate to 83 for the stainless steel. These results provide guidelines for the material choices of a forthcoming locomotion module to be used in the 3 mm 3 mm 3 mm I-SWARM robots. The FPC substrate showed to have the best compatibility to the fabrication processes and the most suitable Q-value of 42. This together with the high deflections makes the FPC the preferred substrate materials the future actuators for the I-SWARM locomotion module. 2008 Elsevier B.V. All rights reserved.

    Keywords
    Piezoelectric actuators, Copolymers, Electric fields, Multilayers, Printed circuit boards, Spin coating
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-108492 (URN)10.1016/j.sna.2008.01.004 (DOI)000256896700010 ()09244247 (ISBN)
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
    2. Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma
    Open this publication in new window or tab >>Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma
    2008 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, no 1, p. 015007-Article in journal (Refereed) Published
    Abstract [en]

    To fully utilize the actuator properties of poly(vinylidenefluoride) (P(VDF))-based polymers, the electric field has to be rather high and one way to accomplish this, in particular with low voltage drive signals, is to build multilayered structures. This paper focuses on how to structure poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) by presenting an etch method to create multilayered miniaturized actuators, with intermediate aluminium electrodes. To create inter-connect areas for the multilayer electrodes, a modified Bosch process in an inductive couple plasma (ICP) etcher is used to remove all P(VDF-TrFE) not covered by the electrodes. Since each electrode mask is slightly different from the others, the result is a staircase-like inter-electrode contact area that is connected from above using a conductive adhesive. The developed ICP etch results in high selective etching and a good agreement between theoretical and measured capacitance values. The manufactured cantilevers, consisting of a multilayer on top of a flexible printed circuit (FPC) board, were tested and the resonant stroke was confirmed to agree with expected values. The successful establishment of interlayer connections between the electrodes open up the possibility for batch fabrication of cheap low voltage micro actuators built on a standard substrate used in millions of commercial products. 2008 IOP Publishing Ltd.

    Keywords
    Multilayers, Actuators, Aluminum, Electric field effects, Electrochemical electrodes, Etching, Inductively coupled plasma, Microfabrication
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-108491 (URN)10.1088/0960-1317/18/1/015007 (DOI)000252965900009 ()09601317 (ISBN)
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13
    3. Quasi-static and dynamic electromechanical response of piezoelectric multilayer cantilever beams
    Open this publication in new window or tab >>Quasi-static and dynamic electromechanical response of piezoelectric multilayer cantilever beams
    2010 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 157, no 2, p. 198-209Article in journal (Refereed) Published
    Abstract [en]

    Piezoelectric multilayer cantilever beams were considered with the aim to establish a simple but general theoretical model, fabricate such beams by a procedure suitable for devices on millimetre scale such as actuators, and study their quasi-static and dynamic electro-mechanical responses. In addition to Euler-Bernoulli assumptions, the beams were assumed to be lossless and have linear piezoelectric response. Four types of beams of nominal length 10 mm, width 2 mm and thickness either 55 or 86 µm, and with two asymmetric configurations of 14 or 15 layers, were fabricated. From top to bottom, each beam consisted of six aluminium electrode layers alternating with five active P(VDF-TrFE) layers, of one passive such layer, and of one polyimide and one copper layer, or vice versa. The thicknesses of the layers and of the beam were determined by use of focused ion beam, scanning electron microscope, light microscope, and Heidenhain probe. Both theoretical and experimental results for resonance frequencies and transverse tip displacement per unit driving voltage showed fair overall agreement from quasi-static conditions to frequencies above the second resonance frequency. Deviations observed are mainly due to variations resulting from the manufacturing process, to nonlinear piezoelectricity and to the presence of losses.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2010
    Keywords
    Cantilever, multilayer, piezoelectric, quasi-static, dynamic, tip deflection, PVDF-TrFE.
    National Category
    Applied Mechanics
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-108496 (URN)10.1016/j.sna.2009.11.013 (DOI)000274979300004 ()
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
    4. Design and manufacturing considerations of low voltage multilayer P(VDF-TrFE) actuators
    Open this publication in new window or tab >>Design and manufacturing considerations of low voltage multilayer P(VDF-TrFE) actuators
    2009 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 11, p. 115019-Article in journal (Refereed) Published
    Abstract [en]

    An actuator unit consisting of three multilayered cantilevers with poly(vinylidene fluoride-trifluoroethylene) on top of a flexible printed circuit board substrate is presented. The multilayer structure has five active polymer layers and six electrodes with an alternating ground and phase configuration. Different aspects regarding processing and deflection advantages, depending on which side of the substrate the multilayer structure is manufactured, are discussed.  One of the cantilever configurations is dynamically modelled using a finite element software and the results are compared to measured values. Because of the combination of a multilayer design and the resonant driving mode, the actuators could be powered by solar cells or used in portable electronics. A 2 V sine wave signal resulted in a tip deflection of 56 μm. To test the unit as a conveyer, speed measurements were conducted. With a 2.5 V square wave signal the speed was 29 µm/s whereas a 8 V signal resulted in 732 µm/s. Motion in all four directions could be confirmed by tuning the frequency of a 10 V square wave signal from 640 Hz to 740 Hz.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing, 2009
    Keywords
    Multilayer, actuator, cantilever, PVDF-TrFE, low voltage, resonating structure
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-108484 (URN)10.1088/0960-1317/19/11/115019 (DOI)000270967800020 ()
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
    5. Resonating low voltage P(VDF-TrFE) multilayered microactuator built on flexible printed circuit board
    Open this publication in new window or tab >>Resonating low voltage P(VDF-TrFE) multilayered microactuator built on flexible printed circuit board
    (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158Article in journal (Refereed) Submitted
    Abstract [en]

    A resonating low voltage microactuator module is presented and evaluated as conveyer. The characterized module has four cantilevers, of which three are used as legs and one as a sensor. A lithographically patterned flexible printed circuit board acts as the passive part of the cantilever whereas the active part consist of 14 layers of spin coated poly(vinylidenefluoride-trifluoroethylene) with alternating evaporated aluminum electrodes. Among the process steps developed are: a batchwise contacting of the multilayer stack, a batchwise polarization method, and an extended polarization procedure. In the final manufacturing step, the legs are bent 60° out of the plane using a folding equipment. The locomotion module is characterized by connecting it with four copper wires and tested with the legs downwards and upside down against a glass plate. Different weights are added to the module and different driving voltage levels and frequencies are tested. The module was found to operate already at 3.0 V peak-to-peak and capable of forward, backward, right and left movement. With wires attached to it, and using a 80 V peak-to-peak square wave signal at 18020 Hz, it could move 150 mg, which is more than 37 times it own weight.

    Keywords
    PVDF-TrFE, conveyer, microrobot, batch polarisation, three legs, resonating operation
    National Category
    Other Materials Engineering Other Materials Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-108485 (URN)
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
    6. Evaluation of building technology for mass producible millimetre-sized robots using flexible printed circuit boards
    Open this publication in new window or tab >>Evaluation of building technology for mass producible millimetre-sized robots using flexible printed circuit boards
    Show others...
    2009 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 7, p. 11pp-Article in journal (Refereed) Published
    Abstract [en]

    Initial tests of a building technology for a compact three-dimensional mass produciblemicrorobot are presented. The 3.9 × 3.9 × 3.3 mm3 sized prototype robot represents amicrosystem with actuators, sensors, energy management and integrated electronics. Theweight of a folded robot is 65 mg and the total volume is less than 23 mm3. The design of theinterfaces of the different modules in the robot, as well as the building technology, isdescribed. The modules are assembled using conductive adhesive with industrial surfacemounting technology on a thin double-sided flexible printed circuit board. The final shape ofthe microrobots is achieved by folding the flexible printed circuit board twice. Electrical andmechanical studies are performed to evaluate the assembly and it is concluded that thetechnology can be used for this type of microsystem. Several issues using the presentedassembly technique are identified and addressed.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing, 2009
    Keywords
    microrobot surface mounting technologies microsystem autonomous flexible printed circuit boards
    National Category
    Manufacturing, Surface and Joining Technology
    Research subject
    Materials Science
    Identifiers
    urn:nbn:se:uu:diva-108482 (URN)10.1088/0960-1317/19/7/075011 (DOI)000267516800034 ()
    Projects
    I-SWARM
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
    7. A vibrating microcantilever sensor for microrobotic applications
    Open this publication in new window or tab >>A vibrating microcantilever sensor for microrobotic applications
    (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439Article in journal (Refereed) Submitted
    Abstract [en]

    In order to actively interact with the environment and to perform advanced tasks, microrobots need to be equipped with sensing tools to detect object and obstacles, and eventually manipulate and transport micro-parts. The concept, design, simulations and first characterization of a simple multifunctional microsystem, a vibrating microcantilever, capable of working as touch sensor and potentially as manipulation tool with feedback sensing is presented. The presented microcantilever was designed to be integrated onboard a microrobot of about 3 × 3 × 3 mm3. The microcantilever is applied as a sensing antenna on the microrobot in order to recognize objects or obstacles through direct contact, causing a voltage drop in a feedback layer. The microcantilever produced is 2.85×0.45×0.098 mm, and the experiments verified that it could be used as a contact sensor featuring high sensitivity with extremely low power consumption and good mass-manufacturability.

    Identifiers
    urn:nbn:se:uu:diva-108495 (URN)
    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
    8. Design and validation of the control circuits for a micro-cantilever tool for a micro-robot
    Open this publication in new window or tab >>Design and validation of the control circuits for a micro-cantilever tool for a micro-robot
    Show others...
    2009 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 153, no 1, p. 76-83Article in journal (Refereed) Published
    Abstract [en]

    The objective of this paper is to present the design and validation of a cantilever-based contact sensing system for a micro-robot. Key elements of the fabrication process of the sensor and the electrical model extraction used to design the control electronics are described. The architecture used for the sensor corresponds to a micro-cantilever fabricated of piezoelectric-polyvinylidene fluoride-trifluoroethylene stacked in a multilayer structure with the possibility of both actuating and sensing. A lumped electro mechanical equivalent model of the micro-cantilever was used to design the control electronics for the cantilever. A driving signal from, the control system is used to vibrate the cantilever at its first mechanical resonance frequency. The control system contains an analog front-end to measure the sensor output signal and a digital control unit designed to track and keep the resonance frequency of the cantilever. By integrating the cantilever control system is integrated in the application specified integrated circuit used to control of the circuit is simplyfied and very compact. Experimental results show a similar behavior between the electrical model and the fabricated system, and the deviations between the model and the measured structure are analyzed. The results also show that the designed control system is capable to detect the resonance frequency of the system and to actuate despite small deviations in process parameters of different batches of cantilevers. The whole system was designed to be integrated into an autonomous micro-robot, although it can be used in other applications.

    Place, publisher, year, edition, pages
    P.O. Box 211, Amsterdam, 1000 AE, Netherlands: Elsevier, 2009
    Keywords
    Vibrating cantilever, Multilayer PVDF-TrFE sensor, Control electronics, Interface circuits
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-108493 (URN)10.1016/j.sna.2009.04.030 (DOI)000267646600012 ()09244247 (ISBN)
    Note

    Compilation and indexing terms, Copyright 2009 Elsevier Inc. 20092412122278 Analog front-end Contact sensing Control circuits Control electronics Digital control units Driving signal Electrical models Electro-mechanical Equivalent model Fabricated system Fabrication process In-process parameters Interface circuits Key elements Mechanical resonance frequency Micro robots Micro-cantilever Multilayer structures Other applications Polyvinylidene fluorides Resonance frequencies Sensor output Trifluoroethylene Vibrating cantilever Whole systems

    Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
  • 24.
    Elgali, Ibrahim
    et al.
    University of Gothenburg.
    Cardemil, Carina
    University of Gothenburg.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Omar, Omar
    University of Gothenburg.
    Thomsen, Peter
    Gothenburg University.
    Biological Effects of Strontium-Doped Calcium Phosphate and Hydroxyapatite Granules during Bone Healing in Normal and Ovariectomised Rats2013Conference paper (Refereed)
  • 25.
    Engqvist, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kraft, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lindqvist, K.
    Ahnfelt, N-O
    Hermansson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Flexural strength measurement of ceramic dental restorative materials2007In: Journal of Advanced Materials, ISSN 1070-9789, Vol. 39, no 1, p. 41-45Article in journal (Refereed)
    Abstract [en]

    Flexural strength of a dental material reflects its ability to withstand tensile stresses and as such has an impact of the fracture risk of a filling. There are several methods to measure flexural strength of a material. The flexural strength of a bioceramic calciumaluminate-based dental restorative material (DoxaDent) has been measured in three different methods with a composite (Tetric Ceram), a glass ionomer cement (Fuji 11) and a phosphate cement (Harward) as references. The three test methods were: a) ISO 4049 for dental composites, three-point bend test of 2*2*25 mm rods, non-polished surface, b) EN 843-1 for ceramic materials, three-point bend test of 3*4*40 mm, polished surface, and c) biaxial ball-on-disc for ceramic materials (ASTM F-394), polished surface. The results obtained clearly show the difficulty in performing flexural strength testing of a bioceramic material. By using the ball-on-disc method the defect size was reduced and thus the resulting flexural strength higher. The strength of DoxaDent tested in the ball-on-disc method is close to the theoretical strength based on the microstructure of the material (maximum grain size of 15 mu m). The composite material and the phosphate cement were rather insensitive to the test method whereas the glass ionomer cement also showed sensitivity towards the test method. Based on fracture mechanics the flexural strength of bioceramic materials is discussed. A modified biaxial test method for evaluation of strength of dental materials in a close to real-life component is proposed.

  • 26.
    Engqvist, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Mapping of mechanical properties of WC-Co using nanoindentation2000In: Tribology letters, ISSN 1023-8883, Vol. 8, no 2-3, p. 147-152Article in journal (Refereed)
    Abstract [en]

    High-resolution measurements of mechanical properties are of immense importance in metallurgy. Measuring the intrinsic properties of each phase separately in multiphase materials gives information that is valuable for the development of new materials and

  • 27.
    Engstrand, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Åberg, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of water content on hardening and handling of a premixed calcium phosphate cement2013In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 33, no 1, p. 527-531Article in journal (Refereed)
    Abstract [en]

    Handling of calcium phosphate cements is difficult, where problems often arise during mixing, transferring tosyringes, and subsequent injection. Via the use of premixed cements the risk of handling complications is reduced. However, for premixed cements to work in a clinical situation the setting time needs to be improved. The objective of this study is to investigate the influence of the addition of water on the properties of premixed cement. Monetite-forming premixed cements with small amounts of added water (less than 6.8 wt.%) were prepared and the influence on injectability, working time, setting time and mechanical strength was evaluated. The results showed that the addition of small amounts of water had significant influence on the properties of the premixed cement. With the addition of just 1.7 wt.% water, the force needed to extrude the cement from a syringe was reduced from 107 (±15)N to 39 (±9)N, the compression strength was almost doubled, and the setting time decreased from 29 (±4)min to 19 (±2)min, while the working time remained 5 to 6 h. This study demonstrates the importance of controlling the water content in premixed cement pastes and how water can be used to improve the properties of premixed cements.

  • 28.
    Eriksson, Olof
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Åberg, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Spens, Erika
    BioArctic Neuroscience AB.
    Nordblom, Jonathan
    Karolinska Institutet, Dept. of Clin. Neuroscience, Division of Clin. CNS research.
    Mattsson, Per
    Karolinska Institutet, Dept. of Clin. Neuroscience, Division of Clin. CNS research.
    Sjödahl, Johan
    BioArctic Neuroscience AB.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Development of Calcium Sulphate Scaffolds Loaded with Acidic Fibroblast Growth Factor for Spinal Cord Repair2009In: European Society for Biomaterials Conference 2009, 2009Conference paper (Refereed)
  • 29.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Combustion Valve Wear: A Tribological Study of Combustion Valve Sealing Interfaces2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The exhaust valve system of combustion engines experiences a very complex contact situation of frequent impact involving micro sliding, high and varying temperatures, complex exhaust gas chemistry and possible particulates, etc. In addition, the tribological situation in the exhaust valve system is expected to become even worse due to strict future emission regulations, which will require enhanced combustion and cleaner fuels. This will substantially reduce the formation of combustion products that might ease the contact conditions by forming tribofilms on the contacting surfaces. The lack of protective films is expected to result in increased wear of the contact surfaces.

    The aim of the work presented in this thesis has been to increase the tribological understanding of the valves. The wear that takes place in the valve sealing interface and how the change in operating conditions affects it have been studied. Such understanding will facilitate the development of future valve designs.

    A test rig has been developed. It has a unique design with the ability to insert ppm amounts of media into a hot air flow, in order to simulate different environmental changes, e.g. varying amount and composition of combustion residue particles.

    PVD coated valves were evaluated in a dry atmosphere. It was concluded that although some of the coatings showed potential, the substrate could not support the thin, hard coatings.

    Investigations with an addition of different oils have been performed. Fully formulated oils proved to build up a protective oil residue tribofilm. This tribofilm has been in-depth analysed and proved to have similar composition and appearance as tribofilms found on low wear field tested valves. With a non-additivated oil, wear particles from the valve seat insert formed a wear particle tribofilm on top of the valve sealing surface. Without any oil the surfaces showed severe wear with wear particles spread over the surfaces.

    The results presented give a hint about what to be expected in the future, when the engine oils are replaced with ash less oils with reduced amount of additives and the consumed amount of oil within the cylinders are reduced. 

    List of papers
    1. Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations
    Open this publication in new window or tab >>Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations
    2014 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 150-155Article in journal (Refereed) Published
    Abstract [en]

    The rapid sharpening of the environmental legislation during the last decades has forced engine manufacturers to radical design modifications. It has been shown that the sliding in the sealing interface is one of the major reasons for wear. The sliding wear is expected to have an even more important role in modern engines. This paper presents unique experimental data, acquired using a dedicated technique in a test-rig. The experimental data is complemented by FEM-simulations. The simulations involve validation of the test-rig valve sealing interface sliding behaviour and investigations on how different parameters influence the sliding length. These parameters include combustion pressure, contact angle, contact length, valve head thickness, coefficient of friction, running-in wear, and change of elastic modulus due to temperature variations.

    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-204452 (URN)10.1016/j.triboint.2013.09.014 (DOI)000328183100017 ()
    Available from: 2013-08-05 Created: 2013-08-05 Last updated: 2018-01-11Bibliographically approved
    2. Wear mechanism study of exhaust valve system in modern heavy duty combustion engines
    Open this publication in new window or tab >>Wear mechanism study of exhaust valve system in modern heavy duty combustion engines
    2011 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 9-10, p. 2477-2484Article in journal (Refereed) Published
    Abstract [en]

    The increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of soot which can build up a protective film are some of the increasing challenges which the system has to endure.

    Three pairs of valves and valve seat inserts with the same material and design properties but with different service condition have been analyzed with a variety of analytical instruments to gain information of how the wear occurs.

    The wear mechanisms found were a combination of oxidation, where many different oxides were found, adhesive wear, which was seen both in form of material transfer and flow lines. On top of Sample Mild and Hard there were tribo films of thickness varying from 1 to 5 mu m consisting of Ca, O, P, S and Zn. The film has in all cases protected the underlying surface from wear but in some cases seems to have a corrosive impact instead.

    Keywords
    Exhaust valve system, Wear, Oxidative, Corrosive, Adhesive
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-162392 (URN)10.1016/j.wear.2010.11.039 (DOI)000294590200162 ()
    Available from: 2011-11-30 Created: 2011-11-30 Last updated: 2017-12-08Bibliographically approved
    3. Combustion valve simulation rig with particle flow
    Open this publication in new window or tab >>Combustion valve simulation rig with particle flow
    (English)In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833Article in journal (Refereed) Submitted
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Identifiers
    urn:nbn:se:uu:diva-201863 (URN)
    Available from: 2013-06-17 Created: 2013-06-17 Last updated: 2018-01-11Bibliographically approved
    4. Wear study of coated heavy duty exhaust valve systems in a experimental test rig
    Open this publication in new window or tab >>Wear study of coated heavy duty exhaust valve systems in a experimental test rig
    2012 (English)In: SAE International technical papersArticle in journal (Refereed) Published
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-173681 (URN)10.4271/2012-01-0546 (DOI)
    Available from: 2012-05-02 Created: 2012-05-02 Last updated: 2018-01-12Bibliographically approved
    5. Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig
    Open this publication in new window or tab >>Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig
    2013 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, p. 1351-1359Article in journal (Refereed) Published
    Abstract [en]

    Increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of particulates which can build up a protective film are some of the increasing challenges which the system has to endure. Thick protective tribofilms found on heavy duty exhaust valve surfaces have been analysed with SEM, TEM, EFTEM, STEM-EDS, Nano-indenter and XPS in order to get a better understanding for the tribofilms properties. Two analysed samples are presented in this paper, from a field service truck and another from atest rig which uses vaporised engine oil to simulate the particle flow. The tribofilms are built upfrom several layers with varying compositions. Most of the material originates from oil additives, but also metallic oxides and other carbon compounds produced in the combustion system. The similarities between the rig generated tribofilm and the tribofilm found on the field tested valve verify the test rig behaviour and opens up for realistic wear testing where the importance ofthe protective tribofilm can be investigated in detail that is not possible in motor tests. 

    Place, publisher, year, edition, pages
    Elsevier, 2013
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials
    Identifiers
    urn:nbn:se:uu:diva-201859 (URN)10.1016/j.wear.2013.01.061 (DOI)000322682800058 ()
    Available from: 2013-06-17 Created: 2013-06-17 Last updated: 2018-01-11Bibliographically approved
    6. The importance of oil and particle flow for exhaust valve wear - An experimental study
    Open this publication in new window or tab >>The importance of oil and particle flow for exhaust valve wear - An experimental study
    2014 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 176-183Article in journal (Refereed) Published
    Abstract [en]

    Oil residue particles have a large impact in protecting the sealing surfaces of heavy duty exhaust valves. To increase the understanding of the mechanism behind this, the wear behavior of exhaust valves subjected to a flow of hot air with controlled amounts of oil particles of three different compositions has been investigated. Air flow without addition of oil was used as a reference. The degree and mechanisms of surface damage proved to be sensitive to the test parameters. Residues from the oils containing additives proved to form protective tribofilms, while the oil without additives promoted agglomeration of wear debris on the sealing surfaces. The dry reference showed severe wear with debris scattered over the surfaces.

    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-204467 (URN)10.1016/j.triboint.2013.09.009 (DOI)000328183100020 ()
    Available from: 2013-08-06 Created: 2013-08-06 Last updated: 2019-09-16
  • 30.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Debord, Dominique
    Scania CV AB.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 150-155Article in journal (Refereed)
    Abstract [en]

    The rapid sharpening of the environmental legislation during the last decades has forced engine manufacturers to radical design modifications. It has been shown that the sliding in the sealing interface is one of the major reasons for wear. The sliding wear is expected to have an even more important role in modern engines. This paper presents unique experimental data, acquired using a dedicated technique in a test-rig. The experimental data is complemented by FEM-simulations. The simulations involve validation of the test-rig valve sealing interface sliding behaviour and investigations on how different parameters influence the sliding length. These parameters include combustion pressure, contact angle, contact length, valve head thickness, coefficient of friction, running-in wear, and change of elastic modulus due to temperature variations.

  • 31.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Elo, Robin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The importance of oil and particle flow for exhaust valve wear - An experimental study2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 176-183Article in journal (Refereed)
    Abstract [en]

    Oil residue particles have a large impact in protecting the sealing surfaces of heavy duty exhaust valves. To increase the understanding of the mechanism behind this, the wear behavior of exhaust valves subjected to a flow of hot air with controlled amounts of oil particles of three different compositions has been investigated. Air flow without addition of oil was used as a reference. The degree and mechanisms of surface damage proved to be sensitive to the test parameters. Residues from the oils containing additives proved to form protective tribofilms, while the oil without additives promoted agglomeration of wear debris on the sealing surfaces. The dry reference showed severe wear with debris scattered over the surfaces.

  • 32.
    Forsberg, Peter