| 1. |
- Carter, Sarah-Sophia, 1994-, et al.
(författare)
-
Medical grade titanium on-chip : assessing the biological properties of biomaterials for bone regeneration
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Medical grade titanium on-chip: assessing the biological properties of biomaterials for bone regeneration Sarah-Sophia D. Carter1, Hugo Nguyen2, Milena Moreira1, Maria Tenje1, and Gemma Mestres11Department of Engineering Sciences, Science for Life Laboratory, Uppsala University, Sweden2Department of Engineering Sciences, Uppsala University, Sweden IntroductionBefore entering the clinic, biomaterials need to be thoroughly evaluated, which requires accurate in vitro models. In this work, we have developed a microfluidic device that could be used to assess the biological properties of biomaterials, in a more in vivo-like environment than what is currently possible. MethodsOur device consists of a polydimethylsiloxane (PDMS, Sylgard 184) microfluidic channel (l= 6 mm, w= 2 mm, h= 200 µm) and a titanium disc (Ti6Al4V, at bottom), held together by an additively manufactured fixture (Fig. 1A). PDMS was cured overnight at 65°C on a silicon wafer master. Once the microchannel and titanium disc were positioned, MC3T3-E1 pre-osteoblast-like cells were seeded (50,000 cells/cm2). After 5 hours incubation under standard culture conditions, flow was started (2 μl/min). As a control, MC3T3-E1 cells were seeded onto plain titanium discs off-chip. Cell viability and morphology were assessed after 20 hours by calcein-AM/propidium iodide (PI), staining live and dead cells respectively. Results and discussionFigure 1B and 1C show calcein-AM/PI stained MC3T3-E1 cells cultured on-chip and figure 1D shows the control, MC3T3-E1 cells cultured off-chip. The potential to culture cells in our chip was confirmed by the presence of a majority of viable cells (green) with a similar morphology as the control sample. The reason for the increased amount of dead cells (red) on-chip compared to the control needs to be further examined, which requires longer-term experiments.ConclusionWe have set the first steps towards a microfluidic tool for the assessment of biological properties of biomaterials.
|
|
| 2. |
|
|
| 3. |
- Fornell, Anna, et al.
(författare)
-
Fabrication of Silicon Microfluidic Chips for Acoustic Particle Focusing Using Direct Laser Writing
- 2020
-
Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 11:2
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed a fast and simple method for fabricating microfluidic channels in silicon using direct laser writing. The laser microfabrication process was optimised to generate microfluidic channels with vertical walls suitable for acoustic particle focusing by bulk acoustic waves. The width of the acoustic resonance channel was designed to be 380 µm, branching into a trifurcation with 127 µm wide side outlet channels. The optimised settings used to make the microfluidic channels were 50% laser radiation power, 10 kHz pulse frequency and 35 passes. With these settings, six chips could be ablated in 5 h. The microfluidic channels were sealed with a glass wafer using adhesive bonding, diced into individual chips, and a piezoelectric transducer was glued to each chip. With acoustic actuation at 2.03 MHz a half wavelength resonance mode was generated in the microfluidic channel, and polystyrene microparticles (10 µm diameter) were focused along the centre-line of the channel. The presented fabrication process is especially interesting for research purposes as it opens up for rapid prototyping of silicon-glass microfluidic chips for acoustofluidic applications.
|
|
| 4. |
- Hirata, Rafael Y. S., et al.
(författare)
-
Platinum nanoparticle-based microreactors protect against the behavioral and neurobiological consequences of chronic stress exposure
- 2022
-
Ingår i: Brain Research Bulletin. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0361-9230 .- 1873-2747. ; 190
-
Tidskriftsartikel (refereegranskat)abstract
- Excitotoxicity is described as the exacerbated activation of glutamate AMPA and NMDA receptors that leads to neuronal damage, and ultimately to cell death. Astrocytes are responsible for the clearance of 80-90% of syn-aptically released glutamate, preventing excitotoxicity. Chronic stress renders neurons vulnerable to excitotox-icity and has been associated to neuropsychiatric disorders, i.e., anxiety. Microreactors containing platinum nanoparticles (Pt-NP) and glutamate dehydrogenase have shown in vitro activity against excitotoxicity. The purpose of the present study was to investigate the in vivo effects of these microreactors on the behavioral and neurobiological effects of chronic stress exposure. Rats were either unstressed or exposed for 2 weeks to an unpredictable chronic mild stress paradigm (UCMS), administered intra-ventral hippocampus with the micro -reactors (with or without the blockage of astrocyte functioning), and seven days later tested in the elevated T -maze (ETM; Experiment 1). The ETM allows the measurement of two defensive responses, avoidance and escape, in terms of psychopathology respectively related to generalized anxiety and panic disorder. Locomotor activity in an open field was also measured. Since previous evidence shows that stress inhibits adult neurogenesis, we evaluated the effects of the different treatments on the number of cells expressing the marker of migrating neuroblasts doublecortin (DCX) in the dorsal and ventral hippocampus (Experiment 2). Results showed that UCMS induces anxiogenic effects, increases locomotion, and decreases the number of DCX cells in the dorsal and ventral hippocampus, effects that were counteracted by microreactor administration. This is the first study to demonstrate the in vivo efficacy of Pt-NP against the behavioral and neurobiological effects of chronic stress exposure.
|
|
| 5. |
- Kubart, Tomas, et al.
(författare)
-
Highly textured AlN thin films on Si by reactive High Power Impulse Magnetron Sputtering
- 2015
-
Ingår i: 42nd ICMCTF 2015 International Conference on Metallurgical Coatings and Thin Films, 20–24 April, San Diego, USA.
-
Konferensbidrag (refereegranskat)abstract
- Piezoelectric AlN films for electroacoustic devices are typically deposited by magnetron sputtering. Sputtering is compatible with standard microelectronic fabrication processes and requires lower deposition temperatures than other techniques. In order to enhance the texture of AlN, metal seed layers, such as molybdenum, are usually used. Low temperature growth of AlN films for devices where the seed layer cannot be used is challenging.Here we report on the growth of thin textured (002) AlN layers directly on Si substrates without any metal seed layer. The films were deposited by reactive High Power Impulse Magnetron sputtering (HiPIMS) from an aluminium target in argon/nitrogen atmosphere. Because in HiPIMS very high degree of ionization of the sputtered material is achieved, this technique provides highly ionized flux to the substrate and thus promotes surface diffusion. Moreover, nitrogen dissociation which occurs in the high density HiPIMS plasma increases reactivity of the nitrogen. For comparison, pulsed DC sputtering was also performed under identical conditions.We show that for 200 nm thick AlN films grown on (100) Si, the HiPIMS process produces well textured (002) films already at room temperature while the pulsed DC films are very poor. At 400°C, which is the optimal temperature for pulsed DC deposition, the HiPIMS films are superior with the FWHM value of 5.1 and 14.2° for the HiPIMS and pulsed DC, respectively. No appreciable stresses were observed in the films. The HiPIMS deposition process is more robust than standard DC sputtering and provides sufficient energy input even for configurations with relatively large target-to-substrate distance. It is therefore suitable also for co-sputtering of ternary nitrides based on AlN.
|
|
| 6. |
- Kubart, Tomas, et al.
(författare)
-
Thin AlN films deposited by reactive HiPIMS and pulsed DC sputtering – a comparative study
- 2014
-
Ingår i: 14th International Conference on Plasma Surface Engineering, September 15 - 19, 2014, Garmisch-Partenkirchen, Germany.
-
Konferensbidrag (refereegranskat)abstract
- High quality wurtzite polycrystalline thin AlN films can be grown at low temperature by reactive magnetron sputtering provided sufficient energy input. Typically, a suitable substrate or a seed layer is used to improve the AlN crystallinity. In this study, thin films grown by pulsed DC (PDCS) and High Power Impulse Magnetron Sputtering (HiPIMS) from an Al target were studied aiming at both higher film quality as well as film deposition in cases where a seed layer is impractical. The deposition process was first characterized with respect to the Ar to N2 gas flow ratio. For selected process conditions, AlN films were prepared with a thickness of about 200 nm. (100) Si and (110) Mo coated Si substrates were used and no intentional substrate heating was employed. The crystalline texture of the AlN films was determined with various XRD techniques.Although the deposition rates with HiPIMS are generally lower than those with PDCS, the transition from metal to compound mode spans over a significantly larger range of N2 gas flow. Therefore, with HiPIMS it is possible to deposit stoichiometric AlN in the transition region at deposition rates comparable with PDCS. Owing to the increased energy input in the HiPIMS process, the film texture is improved which is especially pronounced at low film thicknesses.
|
|
| 7. |
- Lima, L., et al.
(författare)
-
Tantalum Nitride as Promissing Gate Electrode for MOS Technology
- 2010
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 31:1, s. 319-325
-
Tidskriftsartikel (refereegranskat)abstract
- Tantalum nitride (TaN) films have been obtained by DC sputtering deposition, using different nitrogen flow and discharge power on Si substrates. The N2/Ar ratio and sputtering power effects on structural and electrical properties of TaN films were investigated by scan profiler (film thickness and deposition rate), atomic force microscopy (rms roughness and grain size) and four-probe technique (electrical resistivity). The deposition rates, between 4 and 78 nm/min, decreased with an increase of N2/Ar ratio, and electrical resistivities, between 150 and 7500 μΩ.cm, increased. For the best condition for N2/Ar of 0.33 and discharge power of 1000W, low electrical resistivity of 350 μΩ.cm, the rms roughness of 0.8 nm and grain size of 380 nm2 were obtained. This best film has been used as gate electrodes in MOS capacitors, which were fabricated with SiNxOy as gate dielectric. These capacitors were used to obtain capacitance-voltage (C-V) measurements. The flat-band voltage of -1.34 V and effective charge densities of about 1011 cm-2 were extracted from all C-V curves, indicating that the TaN/SiNxOy/Si structures present similar behavior when are compared to those presented in literature. Therefore, our TaN gate electrode can be considered as promising gate electrode for CMOS technology.
|
|
| 8. |
|
|
| 9. |
- Micheal Raj, Pushparani, et al.
(författare)
-
Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies
- 2021
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:47, s. 29859-29869
-
Tidskriftsartikel (refereegranskat)abstract
- Some of the most fundamental chemical building blocks of life on Earth are the metal elements. X-ray absorption spectroscopy (XAS) is an element-specific technique that can analyse the local atomic and electronic structure of, for example, the active sites in catalysts and energy materials and allow the metal sites in biological samples to be identified and understood. A microfluidic device capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions is presented in this work. The device is evaluated at the K-edges of iron and bromine and the L-3-edge of lead, in both transmission and fluorescence mode detection and in a wide range of sample concentrations, as low as 0.001 M. The device is fabricated in silicon and glass with plasma etched microchannels defined in the silicon wafer before anodic bonding of the glass wafer into a complete device. The device is supported with a well-designed printed chip holder that made the microfluidic device portable and easy to handle. The chip holder plays a pivotal role in mounting the delicate microfluidic device on the beamline stage. Testing validated that the device was sufficiently robust to contain and flow through harsh acids and toxic samples. There was also no significant radiation damage to the device observed, despite focusing with intense X-ray beams for multiple hours. The quality of X-ray spectra collected is comparable to that from standard methods; hence we present a robust microfluidic device to analyse liquid samples using synchrotron XAS.
|
|
| 10. |
- Moreira e Silva Bernardes, Maurício, et al.
(författare)
-
Original Design in a Copying-Intensive Industry
- 2017
-
Ingår i: International Journal of Computer Applications. - New York : FCS® (Foundation of Computer Science). - 0975-8887. ; 159:7, s. 29-38
-
Tidskriftsartikel (refereegranskat)abstract
- In some industries, copying is common and extensive. Most literature on the topic focuses on legal issues and interprets copying as a problem. To better understand the copying phenomenon, this study investigates the relationship between copying and design processes in five case companies in a copying-intensive industry. The findings reveal that unlike design processes, copying processes lack early conceptual activities. Furthermore, resources and contact with the end market are found to be prerequisites for professional and strategic design processes, whereas a lack of these better suits copying processes, especially in industries with low product variety and limited design problems.
|
|
