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Numrering	Referens	Omslagsbild	Hitta
1.	Arwin, Hans (författare) Is ellipsometry suitable for sensor applications? 2001 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 92:1-3, s. 43-51 Tidskriftsartikel (refereegranskat)abstract Ellipsometry is a powerful tool for optical characterization of surfaces and thin-films. Very favorable features for sensor applications are the in situ advantage, the possibility to work with non-labeled molecules and the high thickness resolution. Sub-nanometers resolution can be achieved in bioaffinity-based sensing and ppm-sensitivity in gas sensing. Ellipsometric sensor systems are based on monitoring changes in the thickness, the refractive index or the microstructure of a sensing layer. These changes are induced by the substance or process measured. A classification of sensing layers is proposed and discussed. One specific application, gas sensing based on sensor arrays, is discussed in some detail. However, the main objective is to critically discuss the possibilities for sensor applications based on ellipsometric read-out.
2.	Brunahl, J., et al. (författare) Piezoelectric shear mode drop-on-demand inkjet actuator 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 101:3, s. 371-382 Tidskriftsartikel (refereegranskat)abstract We report on comprehensive characterization of piezoelectric shear mode inkjet actuators micromachined into bulk Pb(Zr0.53Ti0.47)O-3 (PZT) ceramics. The paper starts with an overview of different drop-on-demand inkjet systems, whereas the main attention is then turned on particular Xaar-type piezoelectric shear mode inkjet printheads. They are an example of complex microelectromechanical system (MEMS) and comprise a ferroelectric array of 128 active ink channels (75 mum wide and 360 mum deep). Detailed information about fabrication process and principles of operation are given. Since each actuating wall of 128 channels is a piezoelectric capacitor metallized from both sides to be animated by electric pulse, electrical properties of channel walls (CWs) are easy to test and serve as a fingerprint of actuator performance in the virgin state as well as after high voltage/elevated temperature heavy duties. We present several techniques to control manufacturing process and fatigue effects. So, continuous wave and pulsed spectroscopy and hysteresis P-E loop tracing showed that compared to a virgin PZT ceramics state, dielectric permittivity (epsilon') was reduced three times, the loss factor (tan delta) increased from initial 4.8 to 6.6%, remnant polarization decreased by 43%, coercive field increased by 38%, whereas Curie temperature increased from 508 to 560 K after 90,000 cycles of ferroelectric hysteresis P-E loop tracing at 50 Hz at electric field of 88.5 kV/cm. Heat treatment also results in PZT ceramics degradation: appreciable reduction of the coupling coefficient (k(15)) and the degradation of inkjet performance were revealed by optical stroboscope technique: 8.7 and 14% reduction of drop velocity and volume in electrically fatigued actuator, 2.5% reduction of drop velocity and unchanged drop volume in temperature-treated actuators.
3.	Griss, Patrick, et al. (författare) Micromachined barbed spikes for mechanical chip attachment 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 95:03-feb, s. 94-99 Tidskriftsartikel (refereegranskat)abstract We investigated the mechanical attachment of chips to surfaces capable of being penetrated by silicon spike,,. The attachment principle is inspired by fishhooks and arrows. Barbed spikes penetrate a material but offer resistance to detaching forces. Two types of barbed spikes were etched in silicon using deep reactive ion etching (DRIE). The mechanical attachment of both types of barbed spike arrays was measured on non-biological materials (polyethylene foil (PE), aluminium foil and Parafilm(TM)) as well as on human skin. The maximum adhesion force was 1.36 N achieved by a 2 x 2 mm(2) chip containing 64 barbed spikes, 160 mum in length, pressed into PE. Maximum adhesion in skin was 0.54 N. The shape of the two different barb types has significant influence on the detachment forces for non-biological materials.
4.	Jakonis, Darius, et al. (författare) Readout architectures for uncooled IR detector arrays 2000 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 84:3, s. 220-229 Tidskriftsartikel (refereegranskat)abstract The main idea of this paper is to compare the readout architectures for uncooled microbolometer focal plane detector arrays with respect to the detector and readout circuit noise. The comparison is done keeping the total power consumption of all architectures constant. Three CMOS readout architectures with different degree of parallelism are described in this paper: pixelwise, columnwise and serial. The noise model of the readout circuit is given. Also, the optimization for the lowest NETD (noise equivalent temperature difference) and estimation of the self-heating effect is presented.
5.	Klintberg, Lena, et al. (författare) A large stroke, high force paraffin phase transition actuator 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 96:2-3, s. 189-195 Tidskriftsartikel (refereegranskat)abstract An actuator that uses the volume expansion related to the solid-to-liquid phase transition of paraffin wax has been fabricated and evaluated. The actuator consists of a ring-shaped paraffin cavity confined by two joint silicon diaphragms with rigid centers. When the paraffin is melted, the resulting hydrostatic pressure deflects the joined rigid centers in one direction only. The magnitude of the deflection is primarily a function of the geometrical relation between the two diaphragms, giving the opportunity to tailor the behavior of the actuator in a large range. Conventional IC-processing techniques have been used to fabricate a prototype with a width of 68 mm and a thickness of 825 μm. The prototype attained a maximum deflection of ca. 90 μm. Loaded with 3 N it still exhibits a deflection of ca. 75 μm. The device can be used as a thermal switch.
6.	Klintberg, Lena, et al. (författare) A thermally activated paraffin-based actuator for gas-flow control in a satellite electrical propulsion system 2003 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 105:3, s. 237-246 Tidskriftsartikel (refereegranskat)abstract Microstructured silicon devices consisting of three inflatable paraffin-filled, corrugated caddies suspended in springs to minimize thermal losses have been fabricated and evaluated with a valve application in mind. The large volume expansion associated with the thermally induced solid-to-liquid phase transition of paraffin is used to activate the caddies’ diaphragms. Theses components all with a thickness of 600 μm and a diameter of 39 mm, but with three different corrugations, have been fabricated with deep reactive etching (DRIE). Whereas the corrugated diaphragms could endure a deflection larger than 50 μm, only strokes of 15 μm on each side were attained when the components were activated. Together with the valve seats proposed, the investigated devices have a potential in electrical propulsion systems for satellites.
7.	Klintberg, Lena, et al. (författare) Fabrication of a paraffin actuator using hot embossing of polycarbonate 2003 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 103:3, s. 307-316 Tidskriftsartikel (refereegranskat)abstract In this paper a fabrication process for integrating paraffin-actuated structures in polycarbonate is outlined. A paraffin-actuated membrane with a diameter of 2.5 mm, where the volume expansion of 10–15% associated with the solid-to-liquid phase transition of paraffin is utilized, has been fabricated and evaluated. Microstructures fabricated in silicon have via an electroplated nickel mould been replicated in polycarbonate by hot embossing and the resulting structures have been sealed by thermal bonding. The bonding strength was measured by a pressurizing test, and the polycarbonate surfaces were characterized with electron spectroscopy for chemical analysis (ESCA). It was found that the bond strength increased when an oxygen plasma treatment was used prior to bonding. ESCA measurements showed a corresponding increase in oxygen content on the plasma treated surfaces. This procedure also improved the wetting properties. The contact angle between paraffin and polycarbonate decreased from 10° after embossing to about 5° after plasma treatment. The fabricated actuator had a total thickness of 1 mm and the membrane deflected about 140 μm when heating the actuator above the melting point of paraffin. Paraffin wax actuators are possible to integrate in plastic structures making them promising candidates in applications such as disposable microfluidic systems where inexpensive and robust valves and pumps are needed.
8.	Kunz, K., et al. (författare) Highly sensitive triaxial silicon accelerometer with integrated PZT thin film detectors 2001 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 92:03-jan, s. 156-160 Tidskriftsartikel (refereegranskat)abstract This paper reports the first micromachined triaxial single-mass accelerometer with integrated piezoelectric thin film detectors. In addition, the design has a much higher sensitivity than previously presented approaches and is significantly smaller. The keystones of the performance are the use of the highly sensitive PZT material and the deep reactive ion etching (DRIE)-based process flow utilizing silicon-on-insulator (SOI) wafers. The accelerometer consists of a 1.2 mg seismic mass, supported by four 8 mum thick spokes. The charge sensitivity in the vertical direction is 22 pC/g and in the parallel direction 8 pC/g.
9.	Köhler, Johan, et al. (författare) A Hybrid Cold Gas Microthruster System for Spacecraft 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 97-98, s. 587-98 Tidskriftsartikel (refereegranskat)abstract A hybrid cold gas microthruster system suitable for low Δv applications on spacecraft have been developed. Microelectromechanical system (MEMS) components together with fine-mechanics form the microthruster units, intergrating four independent thrusters. These are designed to deliver maximum thrusts in the range of 0.1–10 mN.The system includes three different micromachined subsystems: a nozzle unit comprising four nozzles generating supersonic gas velocity, i.e. 455 m/s, four independent piezoelectric proportional valves with leak rates at 10−6 scc/s He, and two particle filters. The performances of all these MEMS subsystems have been evaluated.The total system performance has been estimated in two parameters, the system-specific impulse and the mass ratio of the propulsion system to the spacecraft mass. These figures provide input for spacecraft design and manufacture.
10.	Melvås, Patrik, et al. (författare) A free-hanging strain-gauge for ultraminiaturized pressure sensors 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; aug-97, s. 75-82 Tidskriftsartikel (refereegranskat)abstract The first entirely surface micromachined free-hanging strain-gauge pressure sensor is presented. The sensing element consists of a 80 pm long H-shaped force transducing beam supported at both ends. The H-shape enables the strain-gauge to be a part of the beam without the need for additional layers. The beam is located beneath and attached at one end to a square polysilicon diaphragm and at the other end to the cavity edge. The diaphragm of the fabricated sensor is 2 mum thick and has a side length of only 100 mum. The new design enables a combination of high pressure sensitivity and miniature chip size as well as good environmental isolation. The pressure sensitivity of the sensor with a H-shaped 0.4 mum thick force transducing beam was measured to be 5 muV/V/mmHg.
11.	Melvås, Patrik, et al. (författare) A temperature compensated dual beam pressure sensor 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 100:1, s. 46-53 Tidskriftsartikel (refereegranskat)abstract The first temperature compensated leverage beam pressure sensor fabricated by surface micromachining is presented. The pressure- sensing element consists of a piezoresistor on an 80 mum x 40 mum x 1 mum double end supported force transducing beam. The beam is located beneath a (100 mum x 100 mum x 2 mum) square polysilicon diaphragm having its ends attached to the diaphragm and to the cavity edge, thus, entirely enclosed inside the vacuum cavity. The thermal compensation piezoresistor is also located in the cavity on a (100 mum x 40 mum x 1 mum beam to achieve nearly identical thermal conditions. Both ends of this beam are attached to the cavity edge and is therefore, pressure-insensitive. The new design enables a combination of high pressure sensitivity (0.8 muV/(V mmHg)), environmental isolation and a decrease of the relative temperature dependency mismatch from 6 to 3% compared to a commercialized traditional piezoresistive pressure sensor.
12.	Niklaus, Frank, et al. (författare) A method to maintain wafer alignment precision during adhesive wafer bonding 2003 Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 107:3, s. 273-278 Tidskriftsartikel (refereegranskat)abstract In this paper, a novel method is presented that prevents aligned wafers from shifting relative to each other during adhesive bonding. The attainable pre-bond wafer alignment accuracy on commercially available bonding equipment is typically 2-5 mum. However, in adhesive wafer bonding, the intermediate adhesive material must exist in a liquid-like state to wet the wafer surfaces and thereby achieve bonding. When pressing the wafers together with the bond chucks during the bonding process it is practically inevitable that shear forces occur, which act in parallel to the bond line. The intermediate liquid adhesive material cannot counteract the shear forces, thus, the wafers move relative to each other. Consequently, the achievable alignment accuracy in adhesive wafer bonding is typically less than 15 mum using commercial bonding equipment. A novel method has been developed that utilises structures at the wafer surfaces to provide areas with solid-state material contact between the two wafers during the bonding process. The resulting frictional forces prevent the wafers from shifting relative to each other during the time the intermediate adhesive material is in a liquid state. Thus, the pre-bond alignment accuracy of 2-5 mum can be maintained during adhesive wafer bonding using standard wafer bonding equipment as compared to a wafer alignment accuracy of 15-50 mum when no frictional structures are used.
13.	Niklaus, Frank, et al. (författare) Low temperature full wafer adhesive bonding of structured wafers 2001 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 92:03-jan, s. 235-241 Tidskriftsartikel (refereegranskat)abstract In this paper, we present a technology for void free low temperature full wafer adhesive bonding of structured wafers. Benzocyclobutene (BCB) is used as the intermediate bonding material. BCB bonds well with various materials and does not release significant amounts of byproducts during the curing process. Thus void-free bond interfaces can be achieved. Cured BCB coatings have an excellent resistance to a variety of acids, alkalines and solvents and a high transparency for light across the visible spectrum, which makes it a good material for fluidic, optical and packaging applications. We demonstrate the fabrication of fluidic structures and the embedding of protruding surface structures. An important finding is that the pre-cured BCB coatings are extremely deformable and have a liquid-like behaviour during bonding.
14.	Oberhammer, Joachim, et al. (författare) Selective wafer-level adhesive bonding with benzocyclobutene for fabrication of cavities 2003 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 105:3, s. 297-304 Tidskriftsartikel (refereegranskat)abstract In this work we describe an adhesive wafer-level bonding technique in which the adhesive material is structured prior to bonding. This technique can be used to create encapsulated cavities of different heights and sizes for surface micromachined devices directly in the bonding layer. Benzocyclobutene (BCB) was used as the adhesive bonding material. The structuring of the BCB was done either by dry etching or by using photosensitive BCB. The process parameters needed to achieve a high bond quality while retaining the shapes of the structures in the intermediate bonding layer have been investigated extensively. Both dry-etch and photosensitive BCB were found to be suitable for selective adhesive bonding. The dry-etch BCB must be soft-baked to a polymerisation degree of 50-60% to both withstand the patterning procedure and to be sticky enough for the following bonding. Soft-baking is not necessary for the photosensitive BCB. For both types of BCB, good bond results have been achieved with a bonding pressure of 2-3 bar and full curing of the BCB at 250 degreesC for I h. Furthermore, helium leak tests have been performed to investigate the suitability of selective adhesive bonding for applications with demands on quasi-hermetic seals. Cavities created with this bonding techniques showed a leak rate between 1.4 x 10(-8) and 4.8 x 10(-8) kg m(2) s(-3) (1.4 x 10(-7) and 4.8 x 10(-7) mbar l s(-1)), which is 3-10 times higher than the limit of MIL-STD 883E. Therefore, this encapsulation technique does not provide sufficient gas-tightness to fulfill the requirements of hermetic electronic encapsulations.
15.	Olsson, Anders, et al. (författare) Numerical and experimental studies of flat-walled diffuser elements for valve-less micropumps 2000 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 84:02-jan, s. 165-175 Tidskriftsartikel (refereegranskat)abstract An investigation of flat-walled diffuser elements for valve-less micropumps is presented. The diffuser element is a small angle flow channel with a rounded inlet and a preferably sharp outlet. The diverging-wall direction is the positive flow direction. The flow-directing capability under steady flow conditions was determined experimentally for several different diffuser elements. The flow-pressure characteristic was studied in detail for one of them. The result is compared with previously published results on pump performance. Numerical simulations were done using the Computational Fluid Dynamics program ANSYS/Flotran. The simulations show the flow-directing capability of the diffuser elements and predict the flow-pressure characteristics well for Reynolds numbers below 300-400. For higher Reynolds numbers, the simulations show the flow-directing capability, but there is a larger discrepancy between simulations and measurements. Simulations were also done for a nozzle element, a wide-angle flow channel with sharp inlet and outlets used in the micropump with dynamic passive-valves. A nozzle element has the converging-wall direction as positive flow direction. The simulations show differences in the flow patterns for diffuser elements and nozzle elements that explain the opposite positive flow directions. The diffuser element has an ordered flow and takes advantage of the pressure recovery in the diverging-wall direction. The nozzle element has gross flow separation in the diverging-wall direction and there is a vena-contracta effect instead of pressure recovery. The effective cross-sectional area is smaller in the diverging-wall direction than in the converging-wall direction.
16.	Pasquariello, Donato, et al. (författare) Surface energy as a function of self-bias voltage in oxygen plasma wafer bonding 2000 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; A82, s. 239-244 Tidskriftsartikel (refereegranskat)abstract A limitation in the use of wafer bonding has been the necessity for high-temperature annealing after contacting the wafers at room temperature. In this paper, we try to find the highest surface energy as a function of self-bias voltage in oxygen plasma-activated wafer bonding, in order to achieve a low-temperature bonding process. The bonding was performed in situ the vacuum chamber. It was found that oxygen plasma has a smoothing effect on the surface roughness, rather independent of the plasma self-bias. However, a moderate self-bias voltage proved to give the highest surface energy for the bonded wafers, both at room-temperature and after annealing at 200°C. We believe that this is due to the fact that a moderate self-bias is the most efficient in removing surface contaminants, like water and hydrocarbons. It was also found that even after annealing at higher temperatures, 480°C and 720°C, the plasma-bonded wafers showed higher surface energy values than wafers bonded in ambient air. This investigation was focused on low-effect plasmas, <200 W, keeping the induced plasma damages at a minimum.
17.	Paulsson, N., et al. (författare) Extraction and selection of parameters for evaluation of breath alcohol measurement with an electronic nose 2000 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 84:3, s. 187-197 Tidskriftsartikel (refereegranskat)abstract The ethanol concentration in realistic breath samples was analyzed using an electronic nose. Conditions were selected so that the samples would reflect those collected in a real drunk driver situation. Hence, parameters such as intake of food and beverage, tobacco habits, as well as the order of participating volunteers were allowed to be variable. The setup was unexpectedly robust towards inter- and intrapersonal variations in breath samples as well as long-term variations. The standard error (16 mol ppm) was the limiting factor but the statistical detection limit was well below 0.1 ppm. The standard error corresponds to between 9% (Austria) and 36% (Sweden) of lowest legally accepted levels. Even though this is regarded as a significant error, there are several options of optimization. Incorporating feature extraction and forward selection together with artificial neural network for prediction of the ethanol concentration showed, besides increasing the accuracy, to be a valuable tool generating feedback of possible improvements of the sensor array.
18.	van der Wijngaart, Wouter, et al. (författare) A high-stroke, high-pressure electrostatic actuator for valve applications 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 100:03-feb, s. 264-271 Tidskriftsartikel (refereegranskat)abstract This paper presents a novel large-stroke electrostatic valve actuator for high-pressure applications. The combination of pressure balancing and flexible electrode structures ensures large flow gaps at a low actuation voltage. A simulation tool was built to evaluate the design parameters. Design specific, as well as general optimisations are performed. The model shows a 5.6 times (theoretical) performance improvement compared to earlier designs. A micromachined test structure was fabricated and evaluated. Measurement results are presented and discussed.
19.	van der Wijngaart, Wouter, et al. (författare) A micropneumatic-to-vibration energy converter concept 2002 Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 100:1, s. 77-83 Tidskriftsartikel (refereegranskat)abstract A new concept for a stand-alone power supply is presented, consisting of a micropneumatic-to-vibration energy converter. The fluidic properties are studied with the help of a simplified model in order to understand the influence of physical parameters on the system's behaviour. Different phenomena causing the energy conversion are discussed. A test structure was fabricated and measurement results are presented.
20.	Abd Hamid, Fatimah Khairiah, et al. (författare) Resistive strain sensors based on carbon black and multi-wall carbon nanotube composites 2024 Ingår i: Sensors and Actuators A-Physical. - : Elsevier. - 0924-4247 .- 1873-3069. ; 366 Tidskriftsartikel (refereegranskat)abstract Strain sensors have garnered considerable interest, particularly in human motion and health monitoring, owing to their high stretchability and sensitivity. In this paper, resistive strain sensors comprising carbon black (CB)/ Ecoflex and multi-wall carbon nanotube (MWCNT)/Ecoflex with high sensitivity and large mechanical strain are presented. These sensors were developed using solution casting and dip-coating techniques. In addition, toluene and acetone were used to enhance the adhesion of CB and MWCNT to the Ecoflex substrate, thereby increasing electrical conductivity, sensitivity, and flexibility of the sensors while maintaining their high stretchability. Toluene-treated strain sensors exhibited the highest sensitivity for both CB/Ecoflex and MWCNT/Ecoflex strain sensors. As a result, the CB/Ecoflex sensor with toluene treatment achieved the highest gauge factor (GF) of -1131, which is 19 times higher than the original samples without surface treatment. Meanwhile, a GF of -106 is exhibited by the MWCNT/Ecoflex sensor, with toluene treatment improving sensitivity by a factor of 2 over untreated samples. These promising findings demonstrate the potential and prospects for flexible and wearable sensor applications.
21.	Akbari, Saeed, et al. (författare) Multimaterial 3D Printed Soft Actuators Powered by Shape Memory Alloy Wires 2019 Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 290, s. 177-189 Tidskriftsartikel (refereegranskat)abstract Shape memory alloys (SMAs) have been widely used to fabricate soft actuators by embedding SMA wires into various soft matrices manufactured by conventional moulding methods or novel three-dimensional (3D) printing techniques. However, soft matrices of SMA based actuators are typically fabricated from only one or two different materials. Here, we exploit the great manufacturing flexibility of multimaterial 3D printing to fabricate various bending, twisting and extensional actuators by precisely controlling the spatial arrangements of different printing materials with different stiffnesses. In order to achieve a broad range of deformations, ten different printing materials were characterized and used in the actuators design. In addition, we developed a finite element model to simulate complex deformations of the printed actuators and facilitate the design process. The model incorporates a user defined material subroutine that describes the nonlinear temperature dependant behavior of SMAs. The results show the efficiency and flexibility of multimaterial 3D printing in tailoring the deformed shape of the SMA based soft actuators, which cannot be accomplished using conventional manufacturing methods such as moulding.
22.	Akbari, Saeed, et al. (författare) Shape memory alloy based 3D printed composite actuators with variable stiffness and large reversible deformation 2021 Ingår i: Sensors and Actuators A-Physical. - : Elsevier B.V.. - 0924-4247 .- 1873-3069. ; 321 Tidskriftsartikel (refereegranskat)abstract Soft composite actuators can be fabricated by embedding shape memory alloy (SMA) wires into soft polymer matrices. Shape retention and recovery of these actuators are typically achieved by incorporating shape memory polymer segments into the actuator structure. However, this requires complex manufacturing processes. This work uses multimaterial 3D printing to fabricate composite actuators with variable stiffness capable of shape retention and recovery. The hinges of the bending actuators presented here are printed from a soft elastomeric layer as well as a rigid shape memory polymer (SMP) layer. The SMA wires are embedded eccentrically over the entire length of the printed structure to provide the actuation bending force, while the resistive wires are embedded into the SMP layer of the hinges to change the temperature and the bending stiffness of the actuator hinges via Joule heating. The temperature of the embedded SMA wire and the printed SMP segments is changed sequentially to accomplish a large bending deformation, retention of the deformed shape, and recovery of the original shape, without applying any external mechanical force. The SMP layer thickness was varied to investigate its effect on shape retention and recovery. A nonlinear finite element model was used to predict the deformation of the actuators.
23.	Alavian Ghavanini, Farzan, 1978, et al. (författare) Controlling the initial phase of PECVD growth of vertically aligned carbon nanofibres on TiN 2011 Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 172:1, s. 347-358 Tidskriftsartikel (refereegranskat)abstract We explore the growth of vertically aligned carbon nanofibers by plasma enhanced chemical vapor deposition, using lithographically defined Ni catalyst seeds on TiN. TiN is selected for being an electrically conducting diffusion barrier suitable for the realization of electronic devices. We show that the rate of Ni diffusion correlates to both the level of oxygen content in the TiN film and to the film resistivity. The synthesis of the nanofibers was characterized using electron microscopy with an emphasis on three growth parameters: substrate temperature, plasma power, and chamber pressure. We propose that a catalyst surface free from carbon deposits throughout the process will induce diffusion-limited growth. The growth will shift towards a supply-limited process when the balance between acetylene, as the effective carbon bearing gas, and atomic hydrogen, as the main etching agent, is skewed in favor of acetylene. This determines whether the dominating growth mode will be vertically aligned tip-type or disordered base-type, by affecting the competition between the formation of the first graphitic sheets on the catalyst surface and at the catalyst-substrate interface
24.	An, Hongbin, et al. (författare) Microfluidic contact lenses for unpowered, continuous and non-invasive intraocular pressure monitoring 2019 Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 295, s. 177-187 Tidskriftsartikel (refereegranskat)abstract Intraocular pressure (IOP) is a crucial physiological indicator of the visual system and play a key role in the diagnosis and treatment of glaucoma. However, the current handheld single measurement tools for IOP sensing cannot meet the future demands for glaucoma management. Thus, here we present the microfluidic contact lens sensors that could provide unpowered, continuous and non-invasive IOP monitoring. The microfluidic contact lens is comprised of a sensing layer of the micropatterned soft-elastomer and a hard plastic reference layer. The devices use the annular sensing chamber filled with the dyed liquid and a sensing microchannel as the IOP transducer. Resulting from the volume variance of the sensing chamber and caused by the deformation of the sensing layer under pressure, the IOP signal is detected as the displacement change of the dyed liquid's interface in the sensing channel, and in which, the displacement change can be optically observed by using the smart-phone camera. Based on the silicone rubber model eyeball, the sensing mechanism of the devices with different design parameters (the position of the sensing chambers and the dimension of the sensing channels) are explored by using the theoretical analyses and experimental investigations. The characteristics of these microfluidic contact lens sensors are tested, in which, the maximum sensitivity of the device (with the sensing chamber of 8.5 mm in diameter and the sensing channel of 100 x 40 um in size) can be achieved to 0.708 mm/mmHg in a working range of 0 (4) over tilde0 mmHg. Also, cyclical tests were conducted and indicated that the devices had a good reversibility and Long-term stability. Furthermore, the device (with the sensing chamber of 5.0 mm in diameter and the sensing channel of 150 x 40 urn in size) was test on the porcine eyes ex vivo, showing a sensitivity of 0.2832 mm/mmHg in a range of 8 (3) over tilde2 mmHg and, the device had a good reproducibility to its IOP change. This work provides a promising approach for unpowered, continuous and non-invasive monitoring of IOP.
25.	Andersson, Martin, et al. (författare) A microfluidic relative permittivity sensor for feedback control of carbon dioxide expanded liquid flows 2019 Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 285, s. 165-172 Tidskriftsartikel (refereegranskat)abstract Binary CO2-alcohol mixtures, such as CO2-expanded liquids (CXLs), are promising green solvents for reaching higher performance in flow chemistry and separation processing. However, their compressibility and high working pressure makes handling challenging. These mixtures allow for a tuneable polarity but, to do so, requires precise flow control. Here, a high-pressure tolerant microfluidic system containing a relative permittivity sensor and a mixing chip is used to actively regulate the relative permittivity of these fluids and indirectly—composition. The sensor is a fluid-filled plate capacitor created using embedded 3D-structured thin films and has a linearity of 0.9999, a sensitivity of 4.88 pF per unit of relative permittivity, and a precision within 0.6% for a sampling volume of 0.3 μL. Composition and relative permittivity of CO2-ethanol mixtures were measured at 82 bar and 21 °C during flow. By flow and dielectric models, this relationship was found to be described by the pure components and a quadratic mixing rule with an interaction parameter, kij, of -0.63 ± 0.02. Microflows with a relative permittivity of 1.7–21.4 were generated, and using the models, this was found to correspond to compositions of 6–90 mol % ethanol in CO2. With the sensor, a closed loop control system was realised and CO2-ethanol flows were tuned to setpoints of the relative permittivity in 30 s.

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