| 1. |
- Rosengren, Agneta, et al.
(författare)
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Tissue reactions evoked by porous and plane surfaces made out of silicon and titanium.
- 2002
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Ingår i: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2531 .- 0018-9294. ; 49:4, s. 392-399
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Tidskriftsartikel (refereegranskat)abstract
- Square-shaped silicon or titanium implants with plane or porous surfaces surrounded by a rim of silicone were implanted in the rat abdominal wall for evaluation of the tissue response after one, six, or 12 weeks. Cell damage was identified as increased membrane permeability using fluorescence microscopy by injection of propidium iodide prior to the killing of the rats. Capsule thickness and immunohistochemical quantification of macrophages were used as a further measure of the foreign-body reaction. There were no significant differences in capsular cell densities for macrophages, total cells (macrophages, fibroblasts, and other cells), or necrotic cells at the different time points for the four surfaces studied. However, significant differences in the kinetics of the response were found between plane surfaces compared with porous ones. Both types of plane surfaces developed a significant increase in capsule thickness over time in contrast to the porous implants. Porous silicon displayed a significant decrease in total cells in the reactive capsule over time. Furthermore, porous silicon and titanium surfaces displayed a significant decrease in total cell numbers at the implant interface between six and 12 weeks. The present study demonstrated that implanted silicon elicited soft-tissue reactions comparable to that of titanium
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| 2. |
- Auzelyte, Vaida, et al.
(författare)
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The beam blanking system for microlithography at Lund Nuclear microprobe
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 485-489
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Tidskriftsartikel (refereegranskat)abstract
- A new beam blanking system was installed at the Lund Nuclear Microprobe and employed in proton beam lithography (PBL) for polymer microstructures fabrication. The blanker consists of two parallel plates connected to a high voltage generator. Measurement of the beam blanking time on a sample was performed by means of the standard PIXE system. The beam is blanked and returns to a sample within 200 ns. The blanking system is designed for the new sub-micrometer beamline under installation in the accelerator laboratory. A number of pilot MeV ion beam lithography experiments were performed to illustrate the possibility to use the blanking system in combination with the existing data acquisition and scanning system. A 2.5 MeV proton beam was used to irradiate 50 mum SU-8 negative resist. The blanker was shown to be a necessary part of the lithography system. It enables blanking between each pixel and hence fabrication of various patterns down to a single pixel. The blanker has significantly simplified beam control and enhanced process time and spatial resolution. Three-dimensional microstructures with 20:1 aspect ratio were fabricated.
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| 3. |
- Bergkvist, Jonas, et al.
(författare)
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Improved chip design for integrated solid-phase microextraction in on-line proteomic sample preparation
- 2002
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Ingår i: Proteomics. - 1615-9861. ; 2:4, s. 422-429
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Tidskriftsartikel (refereegranskat)abstract
- A recently introduced silicon microextraction chip (SMEC), used for on-line proteomic sample preparation, has proved to facilitate the process of protein identification by sample clean up and enrichment of peptides. It is demonstrated that a novel grid-SMEC design improves the operating characteristics for solid-phase microextraction, by reducing dispersion effects and thereby improving the sample preparation conditions. The structures investigated in this paper are treated both numerically and experimentally. The numerical approach is based on finite element analysis of the micro-fluidic flow in the microchip. The analysis is accomplished by use of the computational fluid dynamics-module FLOTRAN in the ANSYS(R) software package. The modeling and analysis of the previously reported weir-SMEC design indicates some severe drawbacks, that can be reduced by changing the microextraction chip geometry to the grid-SMEC design. The overall analytical performance was thereby improved and also verified by experimental work. Matrix-assisted laser desorption/ionization mass spectra of model peptides extracted from both the weir-SMEC and the new grid-SMEC support the numerical analysis results. Further use of numerical modeling and analysis of the SMEC structures is also discussed and suggested in this work.
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| 4. |
- Ekström, Simon, et al.
(författare)
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Integrated selective enrichment target - a microtechnology platform for matrix-assisted laser desorption/ionization-mass spectrometry applied on protein biomarkers in prostate diseases
- 2004
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835. ; 25:21-22, s. 3769-3777
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Tidskriftsartikel (refereegranskat)abstract
- The performance of a miniaturized sample processing platform for matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS), manufactured by silicon microfabrication, called integrated selective enrichment target (ISET) technology was evaluated in a biological context. The ISET serves as both sample treatment device and MALDI-MS target, and contains an array of 96 perforated nanovials, which each can be filled with 40 nL of reversed-phase beads. This methodology minimizes the number of sample transfers and the total surface area available for undesired adsorption of the analytes in order to provide high-sensitivity analysis. ISET technology was successfully applied for characterization of proteins coisolated by affinity chromatography of prostate-specific antigen (PSA) from human seminal fluid. The application of ISET sample preparation enabled multiple analyses to be performed on a limited sample volume, which resulted in the discovery that prolactin inducible protein (PIP) was coisolated from the samples.
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| 5. |
- Ekström, Simon, et al.
(författare)
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On-chip microextraction for proteomic sample preparation of in-gel digests
- 2002
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Ingår i: Proteomics. - 1615-9861. ; 2:4, s. 413-421
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Tidskriftsartikel (refereegranskat)abstract
- Despite the high sensitivity and relatively high tolerance for contaminants of matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) there is often a need to purify and concentrate the sample solution, especially after in-gel digestion of proteins separated by two-dimensional gel electrophoresis (2-DE). A silicon microextraction chip (SMEC) for sample clean-up and trace enrichment of peptides was manufactured and investigated. The microchip structure was used to trap reversed-phase chromatography media (POROS R2 beads) that facilitates sample purification/enrichment of contaminated and dilute samples prior to the MALDI-TOF MS analysis. The validity of the SMEC sample preparation technique was successfully investigated by performing analysis on a 10 nM peptide mixture containing 2 m urea in 0.1 m phosphate-buffered saline with MALDI-TOF MS. It is demonstrated that the microchip sample clean-up and enrichment of peptides can facilitate identification of proteins from 2-DE separations. The microchip structure was also used to trap beads immobilized with trypsin, thereby effectively becoming a microreactor for enzymatic digestion of proteins. This microreactor was used to generate a peptide map from a 100 nM bovine serum albumin sample.
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| 6. |
- Törndahl, Marcus, et al.
(författare)
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Characterisation and comparison of a cMUT versus a piezoelectric transducer for air applications
- 2002
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Ingår i: 2002 IEEE Ultrasonics Symposium. Proceedings (Cat. No.02CH37388). - 0780375823 ; , s. 1023-1026
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Konferensbidrag (refereegranskat)abstract
- The main objectives with this investigation are firstly to compare important parameters of a capacitive micromachined ultrasonic transducer (cMUT) for air applications with a corresponding piezoelectric ultrasonic transducer. Secondly, to characterise the cMUT's radiation field using light diffraction tomography. The cMUTs consist of a silicon backplate with small pyramid-shaped cavities and a metallised polymeric membrane. The piezoelectric transducers are nonfocused with a resonance frequency of 450 kHz. Time waveforms, FFT-spectra, S/N-ratio, linearity plots and distance working range are presented for different kinds of combinations of cavity size, membrane thickness and bias voltage. Pressure maps from light diffraction tomography measurements are also presented. The principal conclusions are that the cMUTs have comparable linearity and sensitivity but exhibit superior bandwidth to the compared piezoelectric transducers
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| 7. |
- Wallman, Lars, et al.
(författare)
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Autonomous protein sample processing on-chip using solid-phase microextraction, capillary force pumping, and microdispensing
- 2004
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835. ; 25:21-22, s. 3778-3787
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Tidskriftsartikel (refereegranskat)abstract
- A capillary force filling microsystem consisting of a chip-integrated solid-phase microextraction (SMEC) array and a microdispenser for sample purification and trace enrichment of peptides is described. The microextraction array was loaded with solid-phase media (50 mum Poros R2 beads) for purification and enrichment of proteomic samples. Samples bound to the SMEC were eluted in a volume of 200 nL. A piezoelectric microdispenser was docked to the array and the samples bound to the SMEC were eluted in a volume of 200 nL using capillary forces. The purified and enriched samples were dispensed onto the matrix-assisted laser desorption/ionization (MALDI) target, providing quality data from samples in the picomolar range. The nanoproteomic platform was compared to corresponding commercial preparation protocols, showing higher mass spectrometry (MS) signal intensities for peptides generated from an alpha-casein digest. The platform was also elvaluated with regards to two-dimensional (2-D) gel-derived protein digests from both fibroblast and epithelial target cells.
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| 8. |
- Wallman, Lars, et al.
(författare)
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Electrochemical etch-stop technique for silicon membranes with p- and n-type regions and its application to neural sieve electrodes
- 2002
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317. ; 12:3, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- In this study the field effects on electrochemic ally controlled silicon etching in KOH during three- and four-electrode pn etch-stop have been investigated. When a p-doped bulk area is surrounded by n-doped silicon and the n-doped silicon is electrochemic ally passivated, small lines of bulk silicon in between the n-doped silicon would not etch. The size of the bulk silicon that did not etch could be moderated by the applied potential on the n-doped silicon during pn etching. For the three-electrode system the size of the electric field passivated bulk silicon could be controlled for line widths ranging between 60 and 100 mum. When a four-electrode system was used and the p-doped bulk silicon was forced to a more negative potential, it was possible to etch lines of bulk silicon down to 40 mum widths. This field-restricted pn etch-stop can be used for fabricating thin membrane structures with densely spaced n-doped regions that can be individually addressed by electronics. One application is the fabrication of neural sieve electrodes which comprise a pn etch-stopped membrane containing several phosphorous-doped individually addressable recording electrodes.
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| 9. |
- Wallman, Lars
(författare)
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Silicon neural interfaces -Design and biomedical aspects-
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis covers the development of a silicon neural interface, with focus on silicon sieve electrode fabrication, design, nerve regeneration, signal recording and biocompatibility. A study of how the via hole size and transparency of the perforated sieve membrane influences the nerve regeneration is presented together with a study on soft tissue responses to planar and porous silicon. A method to characterise the electric properties of different sieve electrode configurations in vitro is presented. The development and fabrication of silicon neural interfaces is also described. In vivo, the sieve electrode is implanted between the proximal and distal stumps of a transected nerve, allowing the nerve fibres to regenerate through the sieve and establish a physical contact with microelectrodes on the sieve membrane. Successful regeneration in the peripheral nerve showing registrations of compound action potentials in the rat sciatic nerve are reported. Sieve electrodes with different via hole sizes and transparencies were implanted in the rat sciatic nerve for 12 weeks. It was found that a better nerve regeneration was achieved in configurations with a high transparency (30 %) and small holes (30 µm). Also neural regeneration through a sieve electrode has been demonstrated at spinal cord level. Since sieve electrodes are intended for chronic use the tissue response evoked by the electrode is of importance. Planar and porous silicon elicited a tissue response similar to that observed for titanium. Porous silicon and porous titanium induced a smaller capsule formation as compared to planar implants. Different methods to microfabricate silicon sieve electrodes are also reported. Standard anisotropical etching in KOH was used to etch the pyramid shaped via holes and phosphorous doping was used to generate the neural recording electrodes. To increase the degree of transparency the pn etch stop technique was used to fabricate thin (7 µm) perforated membranes. To be able to integrate individual phosphorous doped recording electrodes on the perforated pn etched stopped membrane a new electrochemical etch process was introduced, i.e. field restricted pn etch stop. Porous silicon is also investigated as a neural electrode material, showing improved impedance characteristics i.e. a high electrode interface capacitance as compared to non-porous silicon electrodes. The findings of a suitable sieve electrode transparency and hole size, improved electrode characteristics and biomaterial properties gives indications for the next generation sieve electrodes.
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| 10. |
- Wallman, Lars, et al.
(författare)
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The geometric design of micromachined silicon sieve electrodes influences functional nerve regeneration
- 2001
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Ingår i: Biomaterials. - 1878-5905. ; 22:10, s. 1187-1193
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Tidskriftsartikel (refereegranskat)abstract
- A neural interface could be used to control a limb prosthesis. Such an interface can be created by facilitating axonal regeneration through a sieve electrode and then register nerve signals intended to control the prosthesis. A key question is how to design the electrodes to ensure the best possible regeneration. Our previous studies have indicated that regeneration can be achieved using electrodes with square-shaped, 100×100 μm, via holes (holes that axons will regenerate through). Other reports have indicated a suitable range of these holes between 40 and 65 μm. In the present study we used silicon sieve electrodes with via holes of either 30 or 90 μm. The transparency, i.e. the percentage of the total via hole area, of these electrodes was either 20 or 30%. The electrodes were inserted into a silicone chamber which was used to bridge a gap in a rat sciatic nerve. After 12 weeks of nerve regeneration electrodes with a hole size of 30 μm and a 30% transparency had the most favourable result as judged by the regained gastrocnemius muscle force and the formation of reactive tissue inside the chamber. The sieve electrode transparency is crucial for ensuring regeneration.
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