| 1. |
- Ahmed, S, 1970, et al.
(författare)
-
Fractal-based dual-band small antenna for 2.45 and 5.8 GHz
- 2010
-
Ingår i: 21st Micromechanics and Micro systems Europe workshop, 26-29 September 2010, Enschede, The Netherlands. ; , s. 108-111
-
Konferensbidrag (refereegranskat)abstract
- Small antennas are becoming important andrequired for many domestic and commercial wireless applications.New design and first experimental results confirmingthe simulations of multi-band patch antenna optimized for the2.45 GHz and 5.8 GHz bands are presented. This design isbased on the practical considerations found for our Minkowski-based fractal antenna that predict the influence ofgeometry modifications on the frequency of operation.
|
|
| 2. |
- Rusu, Mircea, 1936, et al.
(författare)
-
Minkowski fractal microstrip antenna for RFID tags
- 2008
-
Ingår i: 38th European Microwave Conference, EuMC 2008; Amsterdam; Netherlands; 27 October 2008 through 31 October 2008. - 9782874870064 ; , s. 666-669
-
Konferensbidrag (refereegranskat)abstract
- The unique properties of fractals have been exploited to develop a new class of antenna element designs that are multi band and compact in size. These properties are very important for RFID (Radio Frequency IDentification) tags where the small size, planar geometries, multi band operation and low cost are essential for many applications. This paper presents a one loop Minkowski modified antenna using a unique configuration and operating at 868MHz and 2.45 GHz that has been realized on a Rogers Duroid substrate. Experimental results confirm the theoretical prediction. In addition, the principle applied in this design could be used to create even smaller devices by using different substrates.
|
|
| 3. |
- Alavian Ghavanini, Farzan, 1978, et al.
(författare)
-
A method to evaluate MEMS bonding
- 2006
-
Ingår i: Micro Structure Workshop 2006. ; 1:1, s. 47-B3d
-
Konferensbidrag (refereegranskat)
|
|
| 4. |
|
|
| 5. |
- Arndt, Holger, et al.
(författare)
-
Real-time constant monitoring of fall risk index by means of fully-wireless insoles
- 2017
-
Konferensbidrag (refereegranskat)abstract
- Constant monitoring of gait in real life conditions is considered the best way to assess Fall Risk Index (FRI) since most falls happen out of the ideal conditions in which clinicians are currently analyzing the patient's behavior. This paper presents the WIISEL platform and results obtained through the use of the first full-wireless insole devices that can measure almost all gait related data directly on the feet (not in the upper part of the body as most existing wearable solutions). The platform consists of a complete tool-chain: insoles, smartphone & app, server & analysis tool, FRI estimation and user access. Results are obtained by combining parameters in a personalized way to build individual fall risk index assessed by experts with the help of data analytics. New FRI has been compared with standards that validate the quality of its prediction in a statistically significant way. That qualitatively relevant information is being provided to the platform users, being either end-users/patients, relatives or caregivers and the related clinicians to ideally assess about their long term evolution. © 2017 The authors and IOS Press.
|
|
| 6. |
- Bjurstrom, Johan, et al.
(författare)
-
Energy harvesting feasibility for safety belt buckle
- 2024
-
Ingår i: 2024 IEEE Wireless Power Technology Conference and Expo (WPTCE). - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350349139 ; , s. 409-413
-
Konferensbidrag (refereegranskat)abstract
- Technology is to an increasing degree becoming spatially distributed, as Internet of Things or sensors in vehicles. With this comes challenges in power supply, with either cumbersome amounts of batteries or power cables. In this paper we examine the potential of energy harvesting for powering a safety sensor on a belt buckle. Concluding that that the vibrations on this site are impractically small, we propose an energy harvester for transducing human induced mechanical energy. The electromagnetic energy harvester converts vertical buckle-in/-out events into rotations of a circular array of magnets, varying the flux through a coil. Both measurements and simulations are performed, the later showing a potential energy of 4mJ for a single buckle-in event. © 2024 IEEE.
|
|
| 7. |
- Bjurström, Johan, et al.
(författare)
-
Tunable spring balanced magnetic energy harvester for low frequencies and small displacements
- 2022
-
Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 259
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a novel concept to efficiently harvest vibrational energy at low frequencies and very small displacement. We describe and evaluate an electromagnetic energy harvester which generates power from a magnetic circuit with motion induced variations of an air gap. External vibrations induce oscillations of the gap length around an equilibrium point, due to a linear spring counteracting the magnetic force. The relative position of the spring can be adjusted to optimize the harvester output for excitation amplitude and frequency. A simulation model is built in COMSOL and verified by comparison with lab measurements. The simulation model is used to determine the potential performance of the proposed concept under both harmonic and non-harmonic excitation. Under harmonic excitation, we achieve a simulated RMS load power of 26.5 μW at 22 Hz and 0.028 g acceleration amplitude. From a set of comparable EH we achieve the highest theoretical power metric of 1712.2 µW/cm3/g2 while maintaining the largest relative bandwidth of 81.8%. Using measured non-harmonic vibration data, with a mean acceleration of 0.039 g, resulted in a mean power of 52 μW. Moreover, the simplicity and robustness of our design makes it a competitive alternative for use in practical situations.
|
|
| 8. |
- Bjurström, Johan, 1985, et al.
(författare)
-
Unified Modeling and Analysis of Vibration Energy Harvesters under Inertial Loads and Prescribed Displacements
- 2022
-
Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417 .- 1454-5101. ; 12:19
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we extend the optimization analysis found in the current literature for single-degree-of-freedom vibrational energy harvesters. We numerically derive and analyze the optimization conditions based on unified expressions for piezoelectric and electromagnetic energy harvesters. Our contribution lies in the detailed analysis and comparison of both resonant and anti-resonant states while fully including the effect of intrinsic resistance. We include both the case of excitation by inertial load and prescribed displacement, as the latter has not been elaborated on in the previous literature and provides new insights. We perform a general analysis but also consider typical values of applied piezoelectric and electromagnetic energy harvesters. Our results improve upon previous similar comparative studies by providing new and useful insights regarding optimal load, load power and power input to output efficiency. Our analysis shows an exponential increase in the critical mechanical quality factor due to the resistive loss coefficient. We find that the ratio of mechanical quality factor to resistive loss coefficient, at resonance, increases drastically close to the theoretical maximum for load power. Under the same optimization conditions, an equivalent conclusion can be drawn regarding efficiency. We find that the efficiency at anti-resonance behaves differently and is equal to or larger than the efficiency at resonance. We also show that the optimal load coefficient at resonance has a significant dependence on the mechanical quality factor only when the resistive loss coefficient is large. Our comparison of excitation types supports the previous literature, in a simple and intuitive way, regarding optimal load by impedance matching and power output efficiency. Our modeling and exploration of new parameter spaces provide an improved tool to aid the development of new harvester prototypes.
|
|
| 9. |
- Castillejo, Pedro, et al.
(författare)
-
Aggregate Farming in the Cloud : The AFarCloud ECSEL project
- 2020
-
Ingår i: Microprocessors and microsystems. - : Elsevier B.V.. - 0141-9331 .- 1872-9436. ; 78
-
Tidskriftsartikel (refereegranskat)abstract
- Farming is facing many economic challenges in terms of productivity and cost-effectiveness. Labor shortage partly due to depopulation of rural areas, especially in Europe, is another challenge. Domain specific problems such as accurate monitoring of soil and crop properties and animal health are key factors for minimizing economical risks, and not risking human health. The ECSEL AFarCloud (Aggregate Farming in the Cloud) project will provide a distributed platform for autonomous farming that will allow the integration and cooperation of agriculture Cyber Physical Systems in real-time in order to increase efficiency, productivity, animal health, food quality and reduce farm labor costs. Moreover, such a platform can be integrated with farm management software to support monitoring and decision-making solutions based on big data and real-time data mining techniques. © 2020 The Author(s)
|
|
| 10. |
- Enoksson, Peter, 1957, et al.
(författare)
-
Wafer bonding for MEMS
- 2005
-
Ingår i: Proceeding of the 9th International Symposium on Semiconductor Wafer Bonding: Science, Technology and Applic, Canadaations, Quebec City.
-
Konferensbidrag (refereegranskat)
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Johannisson, Pontus, et al.
(författare)
-
Impact-driven up-conversion in piezoelectric MEMS energy harvesters with pulsed excitation
- 2018
-
Ingår i: Journal of Physics. - : IOP Publishing.
-
Konferensbidrag (refereegranskat)abstract
- The potential of impact-driven frequency up-conversion in a MEMS EH is evaluated using numerical simulations. The investigated design is compared to a conventional cantilever EH in terms of output power and loss rate. The upshifting can lead to significantly increased output power at a similar loss rate but as the time scale for the loss is long, the benefit is limited. This also requires an effective upshifting process. The design of the impact introduces a length scale that must be selected with excitation, gravity, and pre-stress taken into account. This makes this type of EH application-dependent as a non-optimal choice may result in low output power.
|
|
| 14. |
- Johannisson, Pontus, et al.
(författare)
-
Multi-axis piezoelectric energy harvesting using MEMS components with slanted beams
- 2016
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 773:1
-
Tidskriftsartikel (refereegranskat)abstract
- During the manufacturing of MEMS components, slanted beams can be produced in the etching process. We show that this can be used to produce skew motion that causes deflection of a proof mass out of the device plane also when the excitation is confined to the device plane. This allows construction of an energy harvester that uses a planar manufacturing process and produces power also with in-plane excitation. To obtain this with traditional methods it would be necessary to manufacture separate components and then mount them with their sensitive axes orthogonal to each other.
|
|
| 15. |
|
|
| 16. |
- Khan, Mohammed Faheem, et al.
(författare)
-
Methods for characterization of wafer-level encapsulation applied on Si to LTCC Anodic bonding
- 2010
-
Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 20:6
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents initial results on generic characterization methods for wafer-level encapsulation. The methods, developed specifically to evaluate anodic bonding of low-temperature cofired ceramics (LTCC) to Si, are generally applicable to wafer-level encapsulation. Different microelectromechanical system (MEMS) structures positioned over the whole wafer provide local information about the bond quality. The structures include (i) resonating cantilevers as pressure sensors for bond hermeticity, (ii) resonating bridges as stress sensors for measuring the stress induced by the bonding and (iii) frames/mesas for pull tests. These MEMS structures have been designed, fabricated and characterized indicating that local information can easily be obtained. Buried electrodes to enable localized bonding have been implemented and their effectiveness is indicated from first results of the novel Si to LTCC anodic bonding.
|
|
| 17. |
- Köhler, Elof, 1980, et al.
(författare)
-
MEMS meander harvester with tungsten proof-mass
- 2019
-
Ingår i: Journal of Physics. - : Institute of Physics Publishing.
-
Konferensbidrag (refereegranskat)abstract
- Using current battery technology the life-time of a leadless pacemaker is approximately 6-10 years, with a large portion of the pacemaker occupied by the battery. This paper investigates the possibility to use a MEMS piezoelectric harvester as a complementary energy source in leadless pacemakers. The challenge is to combine the low resonance frequency required to harvest energy from a heartbeat with the small volume of 20×4×3 mm3 available, with the corresponding harvester displacement restricted to 2 mm. Due to the displacement restriction the selected structure was a double clamped bridge in order to reduce the mass displacement, with various meander-type designs simulated to reduce resonance frequency. To further reduce resonance frequency large proof-masses of tungsten were attached by gluing. Two types of tungsten proof-masses were added to four different harvesters, 16.4 mg and 16.6 mg on sample 1 and 2 and 502 mg and 492 mg proof-mass on sample 3 and 4. The structures have 2 μm patterned PZT (deposited by sol-gel technique) and Pt metal electrodes for d31 mode harvesting. The power output measured from one of the two PZT/electrodes was 0.13 nW with 50 μm deflection at 100 k Ω optimal load resistance and 9.1 mVpp at 232 Hz.
|
|
| 18. |
- Larsson, S., et al.
(författare)
-
Simple method for quality factor estimation in resonating MEMS structures
- 2018
-
Ingår i: Proceedings of the 17th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, 2017. - : IOP Publishing.
-
Konferensbidrag (refereegranskat)abstract
- The quality factor of a packaged MEMS resonating structure depends on both the packaging pressure and the structure's proximity to the walls. This type of mechanical constraints, which causes energy dissipation from the structure to the surrounding air, are applicable for oscillating energy harvesters and should be considered in the design process. However, the modelling of energy losses or the measurements of their direct influence inside a packaged chip is not trivial. In this paper, a simple experimental method to quantify the energy loss in an oscillating MEMS structures due to the surrounding air is described together with preliminary results. The main advantage of the method is the ability to characterize the damping contributions under different vacuum and packaging conditions without requiring any packaging of the harvester chip or fabrication of multiple devices with different cavity depths. © Published under licence by IOP Publishing Ltd.
|
|
| 19. |
- Löfgren, Linus, et al.
(författare)
-
Low-power humidity sensor
- 2008
-
Ingår i: Proceedings of Eurosensors. ; , s. 231-234
-
Konferensbidrag (refereegranskat)
|
|
| 20. |
- Löfgren, Linus, et al.
(författare)
-
Low-power humidity sensor for RFID applications
- 2008
-
Ingår i: 4M2008 Conference, Cardiff, UK.
-
Konferensbidrag (refereegranskat)abstract
- Wireless sensors incorporated in RFID systems are important in several industrial, consumer and logisticsapplications. By extending RFID tags to sensing applications, the products become smarter. Application areas forthese smart tags include; health care (verification of the environmental conditions during transport or in storage of e.g.diapers, bandages, etc.), food monitoring (food quality during transport, storage and sales) and construction industry(e.g. building material).In this paper, a small, very low power and low cost humidity sensor tailor made for passive RFID applications ispresented. The sensor consists of a glass chip substrate with a sub-micron interdigitated gold electrode structurecovered with a humidity sensitive polyimide layer. The humidity absorbed by the sensing layer is measuredcapacitively. Finite element modeling and analytic calculations were used to determine the design of the interdigitatedelectrodes and the optimal thickness of the polyimide layer. A read-out electronics circuit was designed and used toevaluate the sensor. Sensors were fabricated and calibrations have been made to verify their function. The sensorresponse was close to linear from below 20 to above 90 %RH and its response time was proven to be at least as shortas that of the climate chamber, namely 0.1 %RH/s. The concept can easily be adapted to measure a range of otherparameters such as temperature or the presence of certain substances.
|
|
| 21. |
|
|
| 22. |
- Montagnoli, Antonio, et al.
(författare)
-
Non-destructive phenotypic analysis of early stage tree seedling growth using an automated stereovision imaging method
- 2016
-
Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- A plant phenotyping approach was applied to evaluate growth rate of containerized tree seedlings during the precultivation phase following seed germination. A simple and affordable stereo optical system was used to collect stereoscopic red-green-blue (RGB) images of seedlings at regular intervals of time. Comparative analysis of these images by means of a newly developed software enabled us to calculate (a) the increments of seedlings height and (b) the percentage greenness of seedling leaves. Comparison of these parameters with destructive biomass measurements showed that the height traits can be used to estimate seedling growth for needle-leaved plant species whereas the greenness trait can be used for broad-leaved plant species. Despite the need to adjust for plant type, growth stage and light conditions this new, cheap, rapid, and sustainable phenotyping approach can be used to study large-scale phenome variations due to genome variability and interaction with environmental factors.
|
|
| 23. |
- Nafari, Alexandra, 1980, et al.
(författare)
-
Boron at Si/SiO2 interface in SOI wafers and consequences for piezoresistive MEMS devices
- 2008
-
Ingår i: MicroMechanics Europe 2008.
-
Konferensbidrag (refereegranskat)abstract
- BESOI wafers are commonly used for MEMS fabrication and their quality is thus of great importance for the functionality and reliability of the device. It is therefore important to be aware that there is a manufacturing problem with boron impurity at the Si/SiO2 layer in the SOI wafer This impurity is not specified when purchasing the wafer and can alter the background doping up to several μm:s from the BOX, resulting in non-functional piezoresistive devices and unwanted limitation in membrane thickness. In this work we present guidelines on how to detect and counteract this impurity.
|
|
| 24. |
- Nafari, Alexandra, 1980, et al.
(författare)
-
Boron impurity at the Si/SiO2 interface in SOI wafers and consequences for piezoresistive MEMS devices
- 2009
-
Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 1361-6439 .- 0960-1317. ; 19:1, s. 6-
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the electrical performance of piezoresistive devices fabricated on thinned SOI wafers has been investigated. Specifically, SOI wafers manufactured with the standard bond-and-etch back method (BESOI), commonly used for MEMS fabrication, have been studied. Results from electrical measurements and SIMS characterization show the presence of a boron impurity close to the buried oxide, even on unprocessed wafers. If the boron impurity overlaps with the piezoresistors on the device, it can create non-defined pn-junctions and thus allow conduction through the substrate, leading to stray connections and excessive noise. The thickness of the boron impurity can extend up to several μm, thus setting a thickness limit for the thinnest parts of a MEMS device. This work shows how this impurity can fundamentally affect the functionality of piezoresistive devices. Design rules of how to avoid this are presented
|
|
| 25. |
- Nafari, Alexandra, 1980, et al.
(författare)
-
MEMS Sensor for in Situ TEM Atomic Force Microscopy
- 2008
-
Ingår i: Journal of microelectromechanical systems. - : IEEE Press. - 1057-7157 .- 1941-0158. ; 17:2, s. 328-333
-
Tidskriftsartikel (refereegranskat)abstract
- Here, we present a MEMS atomic force microscope sensor for use inside a transmission electron microscope (TEM). This enables direct in situ TEM force measurements in the nanonewton range and thus mechanical characterization of nanosized structures. The main design challenges of the system and sensor are to reach a high sensitivity and to make a compact design that allows the sensor to be fitted in the narrow dimensions of the pole gap inside the TEM. In order to miniaturize the sensing device, an integrated detection with piezoresistive elements arranged in a full Wheatstone bridge was used. Fabrication of the sensor was done using standard micromachining techniques, such as ion implantation, oxide growth and deep reactive ion etch. We also present in situ TEM force measurements on nanotubes, which demonstrate the ability to measure spring constants of nanoscale systems.
|
|
