| 1. |
- Bodén, Roger, et al.
(author)
-
A metallic micropump for high-pressure microfluidics
- 2008
-
In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 18:11, s. 115009-
-
Journal article (peer-reviewed)abstract
- This paper presents one of the strongest mechanical sub-cm(3) sized micropumps for microfluidics. It consists of two active valves and one pumping chamber, each operated by a paraffin actuator that is driven by a low-voltage square pulse waveform. The pump is fabricated in a simple process using parylene-coated stainless steel stencils, paraffin and copper clad polyimide. When driving the pump at 0.07 Hz and 2.0 V (0.8 W) per actuator, it pumped water without leakage at a flow rate of 0.75 mu L min(-1) up to above 50 bar (5 MPa) back-pressure. The frequency dependence was evaluated and a maximum flow rate of 1 mu L min(-1) at 0.21 Hz and 1.8 V was observed. A thermomechanical FEM analysis, which was in good agreement with experiments at low frequencies, predicts the behaviour at higher frequencies.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Evander, Mikael, et al.
(author)
-
Versatile microchip utilising ultrasonic standing waves
- 2005
-
In: IFMBE Proceedings 2005. ; , s. 123-124
-
Conference paper (peer-reviewed)abstract
- This paper presents the concept and initial work on a microfluidic platform for bead-based analysis of biological sample. The core technology in this project is ultrasonic manipulation and trapping of particle in array configurations by means of acoustic forces. The platform is ultimately aimed for parallel multistep bioassays performed on biochemically activated microbeads (or particles) using submicrolitre sample volumes. A first prototype with three individually controlled particle trapping sites has been developed and evaluated. Standing ultrasonic waves were generated across a microfluidic channel by integrated PZT ultrasonic microtransducers. Particles in a fluid passing a transducer were drawn to pressure minima in the acoustic field, thereby being trapped and confined laterally over the transducer. It is anticipated that acoustic trapping using integrated transducers can be exploited in miniaturised total chemical analysis systems (µTAS), where e.g. microbeads with immobilised antibodies can be trapped in arrays and subjected to minute amounts of sample followed by a reaction, detected using fluorescence. Preliminary results indicate that the platform is capable of handling live cells as well as microbeads. A first model bioassay with detection of fluorescein marked avidin binding to trapped biotin beads has been evaluated.
|
|
| 9. |
- Köhler, Johan, et al.
(author)
-
A hybrid cold gas microthruster system for spacecraft
- 2001
-
In: Digest of Papers for the 11th Int Conf on Solid-State Sensors and Actuators - Transducers '01 and Eurosensors XV, Munich, Germany, June 10-14. ; , s. 886-889
-
Conference paper (peer-reviewed)
|
|
| 10. |
|
|
| 11. |
- Lehto, Marcus, et al.
(author)
-
A polymeric paraffin microactuator
- 2008
-
In: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 17:5, s. 1172-1177
-
Journal article (peer-reviewed)abstract
- Paraffin wax is a promising material in microactuators not only because of its ability of producing large displacements and high forces at the same time but also because of the variety of manufacturing techniques available. In this paper, a simple actuator based on paraffin wax as the active material is fabricated and tested. Ultraviolet-curable epoxy is used in a technique combining simultaneous moulding and liquid-phase photopolymerization in a single-process step to build the stiff part of the actuator body. A heater is integrated in the paraffin reservoir, and a polyimide tape is used as the deflecting membrane. Thermornechanical analysis of the paraffin wax shows that it exhibits a volume expansion of 10%, including phase transitions and linear expansion. As for the actuator, a stroke of 90 mu m is obtained for the unloaded device, whereas 37 mu m is recorded with a 0.5-N contact load at a driving voltage of 0.71 V and a frequency of 1/32 Hz. The actuator can be used in microsystems, where both large strokes and forces are needed. The low-cost materials and low driving voltage also makes it suitable for disposable systems.
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Lehto, Marcus, et al.
(author)
-
Rapid prototyping of a polymeric paraffin microactuator
- 2008
-
In: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 17:5, s. 1172-1177
-
Journal article (peer-reviewed)abstract
- Paraffin wax is a promising material in microactuators not only because of its ability of producing large displacements and high forces at the same time but also because of the variety of manufacturing techniques available. In this paper, a simple actuator based on paraffin wax as the active material is fabricated and tested. Ultraviolet-curable epoxy is used in a technique combining simultaneous moulding and liquid-phase photopolymerization in a single-process step to build the stiff part of the actuator body. A heater is integrated in the paraffin reservoir, and a polyimide tape is used as the deflecting membrane. Thermomechanical analysis of the paraffin wax shows that it exhibits a volume expansion of 10%, including phase transitions and linear expansion. As for the actuator, a stroke of 90 mum is obtained for the unloaded device, whereas 37 mum is recorded with a 0.5-N contact load at a driving voltage of 0.71 V and a frequency of 1/32 Hz. The actuator can be used in microsystems, where both large strokes and forces are needed. The low-cost materials and low driving voltage also makes it suitable for disposable systems.
|
|
| 15. |
- Lilliehorn, Tobias, et al.
(author)
-
Array transducer for ultrasonic manipulation of particles
- 2004
-
In: ; , s. 69-72
-
Conference paper (other academic/artistic)abstract
- This paper presents the concept and initial work on a microfluidic platform for bead-based analysis of biological sample. The core technology in this project is ultrasonic manipulation and trapping of particle in array configurations by means of acoustic forces. The platform is ultimately aimed for parallel multistep bioassays performed on biochemically activated microbeads (or particles) using submicrolitre sample volumes. A first prototype with three individually controlled particle trapping sites has been developed and evaluated. Standing ultrasonic waves were generated across a microfluidic channel by integrated PZT ultrasonic microtransducers. Particles in a fluid passing a transducer were drawn to pressure minima in the acoustic field, thereby being trapped and confined laterally over the transducer. It is anticipated that acoustic trapping using integrated transducers can be exploited in miniaturised total chemical analysis systems (µTAS), where e.g. microbeads with immobilised antibodies can be trapped in arrays and subjected to minute amounts of sample followed by a reaction, detected using fluorescence. A first model bioassay with detection of fluorescein marked avidin binding to trapped biotin beads has been evaluated. To enable development of the next generation of 2D array trapping devices, means of microfabricating multilayer ultrasonic array transducers using thick film technology have been developed.
|
|
| 16. |
|
|
| 17. |
- Lilliehorn, Tobias, et al.
(author)
-
Bioassays on ultrasonically trapped microbead clusters in microfluidic systems
- 2004
-
In: Micro Total Analysis Systems 2004. - 0854048960 ; 2, s. 327-329
-
Conference paper (peer-reviewed)abstract
- The handling of biochemically functionalised beads or particles is becoming increasingly important in µTAS. Bead-based analysis of e.g. proteins can be made sensitive due to the large active surface area and flexible by chemical design of the bead surface. We have developed a microfluidic device utilising an array of integrated and individually controlled ultrasonic microtransducers for particle trapping [1]. Particles inserted in the device are subjected to acoustic radiation forces [2] confining them at localised trapping sites. We would now, for the first time at an international conference, like to present a technique for performing bioassays on such ultrasonically trapped beads in microfluidic systems. The microfluidic device is shown in Fig. 1, where the piezoceramic ultrasonic transducers can be seen in the channel crossings in the insert. The device is designed as an acoustic resonator, to obtain localised standing acoustic waves at each transducer with essentially one pressure node in the middle of the 72 µm deep channel when operated near 10 MHz. This configuration is chosen to keep trapped particles away from the interior surfaces of the device, thus enabling fast switching of beads with a minimum in carry-over between assays. The fluidic chip, shown in Fig. 2, is designed to allow injection of microbeads, washing fluid and sample to the three trapping sites. It has been shown that the microbead clusters, as shown in Fig. 3, can be trapped at considerably high perfusion rates, up to 10 µl/min, Fig 4. As a model bioassay, 6.7 µm biotin-covered beads (PC-B-6.0, Gerlinde Kisker, Germany) were injected and transported to one tapping site using washing fluid (water). Activating the transducer trapped the beads. A solution of FITC-tagged avidin was perfused over the bead bed at 3 µl/min, using the corresponding orthogonal sample channel. After 100 s the sample flow was turned off and the bead trap was washed by perfusing water at 3 µl/min. The fluorescence response from the trapped bead clusters was monitored during the assay, and the result is shown in Fig. 5. After excess avidin was washed from the bead trap, a measured step response . indicated that avidin had bound to the beads. Finally the possibility of moving trapped microbeads between the individually controlled trapping sites in the device is shown in Fig. 6, where the transducers are activated sequentially while keeping the bead carrying washing fluid at 3 µl/min during the experiment. Work in the near future will be focused on optimising the device with respect to the bioassay performance, and in a longer perspective on expanding the concept to two dimensions to enable a new dynamic mode of generating bioanalytical arrays.
|
|
| 18. |
|
|
| 19. |
|
|
| 20. |
|
|
| 21. |
- Lilliehorn, Tobias, et al.
(author)
-
Trapping of microparticles in the near field of an ultrasonic transducer
- 2005
-
In: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 43:5, s. 293-303
-
Journal article (peer-reviewed)abstract
- We are investigating means of handling microparticles in microfluidic systems, in particular localized acoustic trapping of microparticles in a flow-through device. Standing ultrasonic waves were generated across a microfluidic channel by ultrasonic microtransducers integrated in one of the channel walls. Particles in a fluid passing a transducer were drawn to pressure minima in the acoustic field, thereby being trapped and confined at the lateral position of the transducer. The spatial distribution of trapped particles was evaluated and compared with calculated acoustic intensity distributions. The particle trapping was found to be strongly affected by near field pressure variations due to diffraction effects associated with the finite sized transducer element. Since laterally confining radiation forces are proportional to gradients in the acoustic energy density, these near field pressure variations may be used to get strong trapping forces, thus increasing the lateral trapping efficiency of the device. In the experiments, particles were successfully trapped in linear fluid flow rates up to 1 mm/s. It is anticipated that acoustic trapping using integrated transducers can be exploited in miniaturised total chemical analysis systems (μTAS), where e.g. microbeads with immobilised antibodies can be trapped in arrays and subjected to minute amounts of sample followed by a reaction, detected using fluorescence.
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
- Nilsson, Mikael, et al.
(author)
-
Ultrasonic beadtrapping for bioassays
- 2004
-
In: ; , s. 149-151
-
Conference paper (other academic/artistic)abstract
- This paper proposes a new dynamic mode of generating bioanalytical arrays based on ultrasonic trapping of microbeads in microfluidic systems. As compared to disposable glass slide microarrays, the proposed technology utilises exchangeable microbeads as the solid phase on which bioassays are performed. The use of microbeads in biochemical analysis is advantageous due to the increased surface area and thus the high binding capacity as compared to planar solid surfaces. By the integration of ultrasonic microtransducers in a microfluidic system, we have proved that it is possible to trap and manipulate microbead clusters by making use of acoustic standing wave forces. Functionalised microbeads have been trapped and moved between well-defined positions in a microchannel, thus for the first time showing trapping of microbeads within a flow-through device with individually controlled trapping sites in an array format. A device with three acoustic trapping sites was fabricated and evaluated. The lateral extension of each trapping site was essentially determined by the corresponding microtransducer dimensions, 0.8 x 0.8 mm2. The flow-through volume was approximately 1 µl and the active trapping site volumes about 100 nl each. The strength of trapping was investigated, showing that 50 % of the initially trapped beads were still trapped at a perfusion rate of 10 µl/min. Since the beads determine the chemical functionality in the device a high degree of flexibility is expected. A fluorescence based avidin bioassay was successfully performed on biotin-coated microbeads trapped in the flow-through device, providing a first proof of principle of the proposed dynamic arraying concept. The dynamic arraying is believed to be expandable to two dimensions, thus with a prospect of performing targeted and highly parallel protein analysis in microfluidics.
|
|
| 26. |
|
|
| 27. |
- Simu, Urban, et al.
(author)
-
Analysis of quasi-static and dynamic motion mechanisms for piezoelectric miniature robots
- 2006
-
In: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 132:2, s. 632-642
-
Journal article (peer-reviewed)abstract
- Piezoceramic actuators are often used when there is a need for high precision translation and are therefore of particular interest in the development of miniature robotic systems. In this paper the effect of miniaturisation on two dynamic and two quasi-static motion mechanisms has been experimentally evaluated using a miniature piezoceramic drive unit. The actuator design, comprising six piezoceramic multilayer bimorphs, and the rapid prototype process used to fabricate the monolithic multilayer structure, are described. Experiments show that for a mass of 1-10g, corresponding to the miniature robot considered, it is possible to use both dynamic and quasi-static motion mechanisms. With the present drive unit at low loads, the dynamic motion mechanisms are less demanding and work closer to the ideal case than quasi-static motion mechanisms. At higher loads the opposite will in general be true. Artefacts due to vibrations and bouncing in the vertical direction are the main reason for non-ideal behaviour when a small movable mass is used. In particular, movements generated by mechanisms utilizing a vertical velocity component are sensitive to a low mass. The design parameters to avoid or reduce these artefacts are identified and discussed.
|
|
| 28. |
- Simu, Urban, 1971-
(author)
-
Piezoactuators for Miniature Robots
- 2002
-
Doctoral thesis (other academic/artistic)abstract
- Challenges in the realisation of a miniature robot are both to handle the complexity of such a system, and to cope with effects of the actual reduction in physical size of all the parts. In particular, the mechanisms for locomotion have to be analysed.The main achievements presented in the thesis are the evaluation and the development of fabrication techniques for miniature multilayer piezoceramic actuators, the evaluation of different motion mechanisms for miniature robots, and the development of building techniques for piezo-based miniature robots.New piezoelectric drive units for miniature robots were designed and fabricated. To realize these monolithic devices, the fabrication technique for multilayer piezoceramic structures was further developed and evaluated with respect to the potential for miniaturisation. Introducing milling in the green state as a technique for shaping piezoceramic actuators gave a geometrical freedom without impairing the possibility of miniaturisation. A rapid prototype process was also developed. In this process, green machining in a milling machine was not only used to shape the multilayer structure, but also to pattern the internal electrodes. The first prototype was a multilayer telescopic actuator, which proved to have a displacement amplification of about 5 compared to a multilayer stack.The drive units were used to evaluate different motion mechanisms. Experiments showed that for a mass corresponding to a typical miniature robot, i.e. 1-10 g, it is possible to use both dynamic and quasistatic motion mechanisms. Artefacts due to vibrations were identified as the main reason for non-ideal behaviour when the movable mass is small. Design criteria for robots with small masses are presented.A tethered cm3 miniature robot for micromanipulation was successfully built. Application specific integrated circuits and two drive units were integrated with a particular building technique. Three-axial positioning and manipulating operations were demonstrated, allowing for a 5-axial movement of a tool.
|
|
| 29. |
|
|
| 30. |
- Snis, Niklas, 1978-
(author)
-
Actuators for autonomous microrobots
- 2008
-
Doctoral thesis (other academic/artistic)abstract
- This thesis presents actuators used in autonomous microsystems. Characteristic for all actuators presented is the low drive voltage and the low power consumption. Different motion mechanisms have been studied and applied in various locomotion modules for microrobots. High resolution movement of a monolithic piezoceramic PZT rotational arm module, using a quasi-static motion mechanism, was demonstrated in a 10x10x20 mm3 autonomous robot. The rotational arm comprises multilayer PZT bimorphs and is fabricated by a wet-building technology. The multilayer approach enables operation of the modules at the low drive voltages provided by the robot electronics. In addition a locomotion module has been designed and fabricated based on the above principles. A three-legged locomotion module with piezoceramic unimorphs, moving by tapping the legs against the floor, has been investigated. Characteristics such as low power consumption, high velocities, low drive voltages and a high weight carrying capability were demonstrated using a resonant motion mechanism. Highly miniaturized three-legged locomotion modules were developed for a 3x3x3 mm3 autonomous microrobot. The modules comprise a multilayer structure of the electroactive copolymer P(VDF-TrFE) on a flexible printed circuit board (FPC) substrate. A novel multilayer fabrication process suitable for mass production was used. It is based on sequential deposition of spun cast copolymer with evaporated aluminum electrodes. Reactive ion etching is used to microstructure the copolymer and the FPC. The mechanical deformability of the FPC is exploited when folding the 2D FPC-multilayer assembly into 3D locomotion modules. Locomotion was demonstrated by moving a glass slider corresponding to the robot weight. A modular building technology for microsystems is presented. It uses surface mounting technology and conductive adhesives to assemble modules on a double-sided FPC. Complex geometries were achieved by subsequent folding the FPC. The feasibility of the technology was demonstrated by assembly of the 3x3x3 mm3 autonomous microrobots.
|
|
| 31. |
- Snis, Niklas, et al.
(author)
-
Monolithic fabrication of multilayer P(VDF-TrFE) cantilevers
- 2008
-
In: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 144:2, s. 314-320
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Stenmark, Lars, et al.
(author)
-
Micro machined propulsion components
- 1997
-
In: 2nd Round Table on Micro-Nano Technologies for space, ESTEC, Noordwijk NL.
-
Conference paper (peer-reviewed)
|
|
| 35. |
|
|
