| 1. |
- 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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| 2. |
- Roxhed, Niclas, et al.
(författare)
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A Method for Tapered Deep Reactive Ion Etching using a Modified Bosch Process
- 2007
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 17:5, s. 1087-1092
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method for etching tapered sidewalls in silicon using deep reactive ion etching. The method is based on consecutive switching between anisotropic etching using the Bosch process and isotropic dry etching. By controlling the etch depths of the anisotropic and isotropic etch sessions, the sidewall angle can be controlled over a relatively large range. Tapered sidewalls are useful in microfabrication processes such as metal coating of 3D structures (e. g. for electrical connections or vias), mold tool fabrication or as a tool to compensate for reentrant etching. The method was tested and characterized by etching basic test structures in silicon wafers. Based on the investigated anisotropic and isotropic etch depths the sidewall angle could be varied between 0 degrees (straight vertical) and 36 degrees. The sidewall angle was well predicted by a model using the etch depths as parameters. Due to the alternating etch procedure a scalloping pattern is generated on the sidewalls. By frequent switching and short etch sessions this scalloping can be reduced to less than 1 mu m. The process represents an easy method to tailor the sidewall angle in deep etching of silicon. The etch scheme is run in a single etch system and can be implemented in ICP systems of most manufactures. The method can also be used in conjunction with the standard Bosch process as demonstrated herein, where the method was applied to compensate for reentrant etching of high out-of-plane mesa-structures.
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| 3. |
- Roxhed, Niclas, et al.
(författare)
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Penetration-enhanced ultrasharp microneedles and prediction on skin interaction for efficient transdermal drug delivery
- 2007
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Ingår i: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 16:6, s. 1429-1440
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents penetration-enhanced hollow microneedles and an analysis on the biomechanical interaction between microneedles and skin tissue. The aim of this paper is to fabricate microneedles that reliably penetrate the skin tissue without using penetration enhancers or special insertion tools that were used in the previous studies. The microneedles are made of silicon and feature ultrasharp tips and side openings. The microneedle chips were experimentally tested in vivo by injection of dye markers. To further investigate the penetration, the insertion progression and the insertion force were monitored by measuring the electrical impedance between microneedles and a counter electrode on the skin. The microneedle design was also tested using a novel simulation approach and compared to other previously published microneedle designs. The purpose of this specific part of the paper was to investigate the interaction mechanisms between a microneedle and the skin tissue. This investigation is used to predict how the skin deforms upon insertion and how microneedles can be used to create a leak-free liquid delivery into the skin. The fabricated microneedles successfully penetrated dry living human skin at all the tested sites. The insertion characteristic of the microneedle was superior to an earlier presented type, and the insertion force of a single microneedle was estimated to be below 10 mN. This low insertion force represents a significant improvement to earlier reported results and potentially allows a microneedle array with hundreds of needles to be inserted into tissue by hand.
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| 4. |
- Roxhed, Niclas, et al.
(författare)
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Tapered deep reactive ion etching : Method and characterization
- 2007
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Ingår i: TRANSDUCERS '07 & EUROSENSORS XXI. - NEW YORK : IEEE. - 9781424408412 ; , s. 251-252
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Konferensbidrag (refereegranskat)abstract
- This work presents a method for etching tapered sidewalls in silicon using deep reactive ion etching. The method is based on consecutive switching between anisotropic etching using the Bosch process and isotropic dry etching. By controlling the etch depths of the anisotropic and isotropic etch sessions, the sidewall angle can be controlled over a relatively large range, from 0 degrees (straight vertical) to 36 degrees. Tapered sidewalls are useful in microfabrication processes such as metal coating of 3D-structures (e.g. for electrical connections or vias), mold tool fabrication or as a tool to compensate for reentrant etching. The process represents an easy method to tailor the sidewall angle in deep etching of silicon. The etch scheme is run in a single etch system and can be implemented in ICP-systems of most manufactures. The method can also be used in conjunction with the standard Bosch process as demonstrated herein, where the method was applied to compensate for reentrant etching of high out-of-plane mesa-structures.
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| 5. |
- Samel, Björn, et al.
(författare)
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A Disposable Lab-on-a-chip Platform with Embedded Fluid Actuators for Active Nanoliter Liquid Handling
- 2007
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Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 9:1, s. 61-67
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present the development of a disposable liquid handling lab-on-a-chip (LOC) platform with embedded actuators for applications in analytical chemistry. The proposed platform for nanoliter liquid handling is based on a thermally responsive silicone elastomer composite, consisting of PDMS and expandable microspheres. In our LOC platform, we integrate active dosing, transportation and merging of nanoliter liquid volumes. The disposable platform successfully demonstrates precise sample volume control with smart microfluidic manipulation and on-chip active microfluidic components. It is entirely fabricated from low-cost materials using wafer-level processing. Moreover, an enzymatic reaction and real-time detection was successfully conducted to exemplify its applicability as an LOC.
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| 6. |
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| 7. |
- Samel, Björn, et al.
(författare)
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A Thermally Responsive PDMS Composite and its Microfluidic Applications
- 2007
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Ingår i: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 16:1, s. 50-57
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a novel composite actuator for controlled liquid actuation in microsystems which is based on a thermally responsive elastomer. The composite actuator consists of expandable microspheres incorporated in a polydimethylsiloxane (PDMS) matrix and entails the merits of both PDMS and expandable microspheres. The main characteristic of the composite actuator is to expand upon heat. The expansion is irreversible and the relative volume increase is measured up to 270% of its original volume after heating to 80 degrees C. The composite was used to fabricate single-use microfluidic pumps and valves. We show the displacement of liquids in the range of nanoliters even against counter pressures up to 100 kPa. Moreover, liquid flow in microchannels was entirely blocked by means of the integrated valves. The valves can withstand pressures up to 140 kPa. The devices are fabricated using low-cost materials only, and the composite actuator allows using wafer-level processing. The fluidic components based on the novel composite are highly integrable and do not require external actuators.
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| 8. |
- Samel, Björn, et al.
(författare)
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Active liquid aspiration and dispensing based on an expanding PDMS composite
- 2007
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Ingår i: PROCEEDINGS OF THE IEEE TWENTIETH ANNUAL INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS. - 9781424409501 ; , s. 802-805
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Konferensbidrag (refereegranskat)abstract
- In this work we present the development of a liquid aspiration and dispensing unit which is based on a single-use thermally expanding PDMS composite. The composite actuator consists of expandable microspheres incorporated into a PDMS matrix and allows for locally altering its topography by means of individually addressable integrated heaters. Devices were designed in order to enable the generation of a cavity by the expansion of the composite actuator and are entirely fabricated from low-cost materials using wafer-level processes only. The fabricated devices successfully demonstrated controlled liquid aspiration and release thereafter of liquid volumes ranging from 180nl to 815nl.
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| 9. |
- Samel, Björn, et al.
(författare)
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Wafer-Level Process for Single-Use Buckling Film Microliter-Range Pumps
- 2007
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Ingår i: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 16:4, s. 795-801
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the development of disposable single-use microfluidic pumps entirely based on a straightforward wafer-level fabrication scheme, which allows for precise integrated active dosing in the microliter range. To accomplish stroke-lengths needed for microliter-range applications, we utilize a new method of bending of a unimorph-composite-actuator film. The unimorph composite actuator consists of a temperature-sensitive silicone elastomer composite, i.e., polydimethylsiloxane, with incorporated expandable microspheres. The fabricated micropumps successfully demonstrated precise liquid-volume control, both at low and high flow rates, and show a standard deviation of 6.7% for consecutive pump experiments. Moreover, the method of fluorescent thermometry was used to measure the thermal load on liquid volumes dispensed with the micropumps. The liquid temperature reaches a maximum of 50 degrees C during the operation. The presented fully integrated single-use micropumps are electrically controllable, do not require external means for liquid actuation, are made of low-cost materials only, and might potentially be used in drug-delivery applications.
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