| 1. |
- Carlborg, Carl Fredrik, et al.
(författare)
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A packaged optical slot-waveguide ring resonator sensor array for multiplex label-free assays in labs-on-chips
- 2010
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 10:3, s. 281-290
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Tidskriftsartikel (refereegranskat)abstract
- We present the design, fabrication, and characterisation of an array of optical slot-waveguide ring resonator sensors, integrated with microfluidic sample handling in a compact cartridge, for multiplexed real-time label-free biosensing. Multiplexing not only enables high throughput, but also provides reference channels for drift compensation and control experiments. Our use of alignment tolerant surface gratings to couple light into the optical chip enables quick replacement of cartridges in the read-out instrument. Furthermore, our novel use of a dual surface-energy adhesive film to bond a hard plastic shell directly to the PDMS microfluidic network allows for fast and leak-tight assembly of compact cartridges with tightly spaced fluidic interconnects. The high sensitivity of the slot-waveguide resonators, combined with on-chip referencing and physical modelling, yields a volume refractive index detection limit of 5 x 10(-6) refractive index units (RIUs) and a surface mass density detection limit of 0.9 pg mm(-2), to our knowledge the best reported values for integrated planar ring resonators.
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| 2. |
- Frisk, Thomas, et al.
(författare)
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A concept for miniaturized 3-D cell culture using an extracellular matrix gel
- 2005
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 26:24, s. 4751-4758
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel method to embed, anchor, and cultivate cells in a controlled 3-D flow-through microenvironment. This is realized using an etched silicon pillar flow chamber filled with extracellular matrix (ECM) gel mixed with cells. At 4 degrees C, while in liquid form, ECM gel is mixed with cells and injected into the chamber. Raising the temperature to 37 degrees C results in a gel, with cells embedded. The silicon pillars both stabilize and increase the surface to volume ratio of the gel. During polymerization the gel shrinks, thus creating channels, which enables perfusion through the chip. The pillars increase the mechanical stability of the gel permitting high surface flow rates without surface modifications. Within the structure cells were still viable and proliferating after 6 days of cultivation. Our method thus makes it possible to perform medium- to long-term cultivation of cells in a controlled 3-D environment. This concept opens possibilities to perform studies of cells in a more physiological environment compared to traditional 2-D cultures on flat substrates.
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| 3. |
- Jacksén, Johan, et al.
(författare)
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Off-line integration of CE and MALDI-MS using a closed-open-closed microchannel system
- 2007
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 28:14, s. 2458-2465
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a new technique for off-line hyphenation between CE and MALDI-MS is presented. Two closed fused-silica capillaries were connected via a silicon chip comprising an open microcanal. The EOF in the system was evaluated using mesityloxide or leucine-enkephalin as a sample and with a running buffer that rendered the analyte neutrally charged. Comparison was made between the EOF in a closed system (first capillary solely included in the electrical circuit) and in a closed-open system (first capillary and microcanal included in the electrical circuit). It was concluded that the experimental values of the EOF agreed with the theory. The influence of the capillary outer diameter on the peak dispersion was investigated using a closed-open-closed system (first capillary, microcanal and second capillary included in the electrical circuit). It was clearly seen that a capillary with 375 mu m od induced considerably higher peak dispersion than a 150 mu m od capillary, due to a larger liquid dead volume in the connection between the first capillary outlet and the microcanal. Mass spectrometric analysis has also been performed following CE separation runs in a closed-open-closed system with cytochrome c and lysozyme as model proteins. It was demonstrated that a signal distribution profile of the separated analytes could be recorded over a 30 mm long microcanal.
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| 4. |
- Nordquist, Lina, 1977-, et al.
(författare)
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Novel microneedle patches for active insulin delivery are efficient in maintaining glycaemic control : an initial comparison with subcutaneous administration
- 2007
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Ingår i: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 24:7, s. 1381-1388
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Good glycaemic control is essential to minimize the risk for diabetes-induced complications. Also, compliance is likely to be higher if the procedure is simple and painless. This study was designed to validate painless intradermal delivery via a patch-like microneedle array. MATERIALS AND METHODS: Diabetes was induced by an intravenous injection of streptozotocin (50 mg/kg bw) in adult male Sprague Dawley rats. Plasma insulin and blood glucose were measured before, during and after subcutaneous or intradermal (microneedles) infusion of insulin (0.2 IU/h) under Inactin-anaesthesia. RESULTS: Before insulin administration, all animals displayed a pronounced hyperglycaemia (19 +/- 1 mM; 359 mg/dl). Administration of insulin resulted in a reduced plasma glucose independently of administration route (subcutaneous 7.5 +/- 4.2, n = 9, and intradermal 11 +/- 1.8, n = 9 after 240 min), but with less errors of the mean in the intradermal group. In the intradermal group, plasma insulin was increased in all latter measurements (72 +/- 22, 81 +/- 34, and 87 +/- 20 microIU/ml), as compared to the first measurement (26 +/- 13). In the subcutaneous group, plasma insulin was elevated during the last measurement (to 154 +/- 3.5 microIU/ml from 21 +/- 18). CONCLUSION: This study presents a novel possibility of insulin delivery that is controllable and requires minimal training. This treatment strategy could improve compliance, and thus be beneficial for patients' glycaemic control.
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| 5. |
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| 6. |
- Oberhammer, Joachim, et al.
(författare)
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Low-voltage high-isolation DC-to-RF MEMS switch based on an S-shaped film actuator
- 2004
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 51:1, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new electrostatically actuated microelectromechanical series switch for switching dc to radio frequency (RF) signals. The device is based on a flexible S-shaped film moving between a top and a bottom electrode in touch-mode actuation. This concept, in contrast to most other microelectrocheinical systems (MEMS) switches, allows a design with a low actuation voltage independent of the off-state gap height. This makes larger nominal switching contact areas for lower insertion loss possible, by obtaining high isolation in the off-state. The actuation voltages of the first prototype switches are 12 V to open, and 15.8 V to close the metal contact. The RF isolation with a gap distance of 14.2 mum is better than -45 dB up to 2 GHz and -30 dB at 15 GHz despite a large nominal switching contact area of 3500 mum(2).
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| 7. |
- Oberhammer, Joachim, et al.
(författare)
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Sealing of adhesive bonded devices on wafer level
- 2004
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 110:1-3, s. 407-412
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Tidskriftsartikel (refereegranskat)abstract
- In this paper. we present a low temperature wafer-level encapsulation technique to hermetically seal adhesive bonded microsystem structures by cladding the adhesive with an additional diffusion barrier. Two wafers containing cavities for MEMS devices were bonded together using benzocyclobutene (BCB). The devices were sealed by a combined dicing and self-aligning etching technique and by finally coating the structures with evaporated gold or PECVD silicon nitride. The sealing layer was inspected visually by SEM and helium leak tests were carried out. Devices sealed with silicon nitride and with known damage of the sealing layer showed a helium leak rate of about 7-14 times higher than the background level. Devices of the same size without damage in the sealing layer had a leak rate of only 1.5 times higher than the background level. Experiments with evaporated gold as cladding layer revealed leaking cracks in the film even up to a gold thickness of 5 mum. The sealing technique with silicon nitride shows a significant improvement of the hermeticity properties of adhesive bonded cavities, making this bonding technique suitable for applications with certain demands on gas-tightness.
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| 8. |
- Rydholm, Susanna, et al.
(författare)
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Microfluidic devices for studies of primary cilium mediated cellular response to dynamic flow conditions
- 2008
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Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 10:4, s. 555-560
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Tidskriftsartikel (refereegranskat)abstract
- We present the first microfabricated microfluidic devices designed specifically for studies of primary cilium mediated cellular response to dynamic flow. The primary cilium functions as a mechano-sensor in renal tubular epithelium, sensing the extracellular fluid flow. Malfunction of cilia has been implicated in e.g. polycystic kidney disease and other pathological conditions. Bending of the primary cilium by fluid flow has been shown to give rise to an intracellular calcium signal, however little is known about the sensitivity to flow duration, magnitude and direction. This paper presents a novel method for studying cilia forming cells in asymmetric microfluidic environments. The microfluidic devices presented here were designed for a dynamic control of the local fluid flow on a cellular level, and thus, enables studies of cellular responses to an amplitude, frequency and direction controlled cilium movement.
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