There are many new microplasma sources being developed for a wide variety of applications, each with different properties tailored to its specific use. Microplasma sources enable portable instruments for, e.g., chemical analysis, sterilization, or activation of substances. A novel microplasma source, based on a microstrip split-ring resonator design with electrodes integrated in its silicon substrate, was designed, manufactured, and evaluated. This device has a plasma discharge gap with a controlled volume and geometry, and offers straightforward integration with other microelectromechancial systems (MEMS) components, e.g., microfluidics. The realized device was resonant at around 2.9 GHz with a quality factor of 18.7. Two different operational modes were observed with the plasma at high pressure being confined in the gap between the electrodes, whereas the plasma at low pressures appeared between the ends of the electrodes on the backside. Measurement of the angular distribution of light emitted from the device with through-substrate electrodes showed narrow emission lobes compared with a reference plasma source with on-substrate electrodes.
This paper presents a reusable microdispenser intended for continuous flow dispensing of variable and controlled volumes of liquid against high back-pressures. The microdispenser consists of two active valves and a dispenser chamber, all actuated by the volume change associated with the solid-to-liquid phase transition of paraffin wax. It is fabricated using stainless steel sheets, a flexible printed circuit board, and a polyimide membrane. All are covered with Parylene C for insulation and fusion bonding at assembly. A finite element method (FEM) model of the paraffin actuator is used to predict the resulting flow characteristics. The results show dispensing of well-defined volumes of 350 and 540 nL, with a good repeatability between dispensing sequences, as well as reproducibility between devices. In addition, the flow characteristics show no back-pressure dependence of the dispensed flow in the interval 0.5--2.0 MPa. The FEM model can be used to predict the flow characteristics qualitatively
A resonating low voltage microactuator module is presented and evaluated as conveyer. The characterized module has four cantilevers, of which three are used as legs and one as a sensor. A lithographically patterned flexible printed circuit board acts as the passive part of the cantilever whereas the active part consist of 14 layers of spin coated poly(vinylidenefluoride-trifluoroethylene) with alternating evaporated aluminum electrodes. Among the process steps developed are: a batchwise contacting of the multilayer stack, a batchwise polarization method, and an extended polarization procedure. In the final manufacturing step, the legs are bent 60° out of the plane using a folding equipment. The locomotion module is characterized by connecting it with four copper wires and tested with the legs downwards and upside down against a glass plate. Different weights are added to the module and different driving voltage levels and frequencies are tested. The module was found to operate already at 3.0 V peak-to-peak and capable of forward, backward, right and left movement. With wires attached to it, and using a 80 V peak-to-peak square wave signal at 18020 Hz, it could move 150 mg, which is more than 37 times it own weight.
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.
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.
The two objectives of this paper are related to the use of n-alkanes in actuators. The first objective is to study the thermomechanics of binary mixtures of dotriacontane and hexatriacontane to see if a quasi-stable thermal expansion can be obtained, and the second one is to find the correspondence between dilatometry [pressure, volume, and temperature (pVT) measurement] and differential scanning calorimetry (DSC). Results show that there is indeed a concentration-dependent plateau in the expansion curves and that the width and horizontal position of this can be adjusted. As compared with pure n-alkanes, the plateaus of the mixtures widen by a factor of 2-4, and as compared with pure hexatriacontane, they shift their low-end temperatures by 5 °C to 10 °C, in the 25% to 75% concentration range. The mixtures' plateaus (gathered around 0.06 cm3/g) are about 0.02 cm3/g below those of the pure n-alkanes. It is shown that DSC can be used for a prediction of the thermomechanical properties of the substances, provided that a pVT reference exists, and the fact that the melting point increases with the pressure that is experienced with the dilatometer is considered. The qualitative similarity between the expansion and enthalpy curves is remarkable. About 25% to 30% of the total volume expansion is attributed to the solid-to-solid phase transition; the rest is attributed to thermal expansion and melting.
The characteristics of one-port aluminum nitride (AlN) Lamb wave resonators utilizing the lowest symmetric (S0) mode with electrically open, grounded, and floating bottom electrode configurations are theoretically and experimentally investigated. The finite element analysis (FEA) is performed to take an insight into the static capacitance characteristics of the AlN Lamb wave resonators with various bottom surface conditions. The theoretical results predict that the floating bottom electrode efficiently reduces the static capacitance in the AlN thin plate and then promotes an efficient improvement in the effective coupling coefficient. Experimentally the AlN Lamb wave resonator without a bottom electrode exhibits a loaded quality factor (Q) as high as 3033 at its series resonance frequency, 948.1 MHz, but a low effective coupling coefficient of 0.18%. On the contrary, the Lamb wave resonator with an electrically floating bottom electrode shows an effective coupling coefficient up to 1.05% but a low loaded Q of 850 at its series resonance frequency, 850.3 MHz. In contrast to the floating bottom electrode, the Lamb wave resonator with an electrically grounded bottom electrode shows a smaller effective coupling coefficient of 0.78% and a similar loaded Q of 800 at the series resonance frequency, 850.5 MHz.
Presented in this paper is a finite-element-method-based model for phase change material actuators, modeling the active material as a fluid as opposed to a solid. This enables the model to better conform to localized loads and offering the opportunity to follow material movement in enclosed volumes. Modeling, simulation, and analysis of an electrothermally activated paraffin microactuator have been conducted. The paraffin microactuator used for the analysis in this study exploits the large volumetric expansion of paraffin upon melting, which, combined with its low compressibility in the liquid state, allows for high hydraulic pressures to be generated. The purpose of this study is to supply a geometry-independent model of such a microactuator through the implementation of a fluid model rather than a solid one, which has been utilized in previous studies. Numerical simulations are conducted at different frequencies of the heating source and for different geometries of the microactuator. The results are compared with the empirical data obtained on a close to identical paraffin microactuator, which clearly show the advantages of a fluid model instead of a solid-state approximation.
In this paper, the strongest yet latchable valve in subcubic-centimeter size for microfluidic applications is presented. The device has an integrated actuator cavity consisting of three segments filled with paraffin, each operated by a separate heater. At one of the segments, a membrane valve head is deflected by the expansion of the resistively melted paraffin to close against its valve seat. Different heating sequences provide a latched closed or opened valve. The maximum pressure before any leakage occurred was 2.5 MPa. The leak pressure is found to be progressively dependent on the clamping pressure applied. The valve has an opening and closing time of 7 and 1 s, respectively. At an applied pressure of 0.3 MPa, the closed valve needs to be reactivated every 100 min to remain leakage free, leading to an average power consumption of 4.5 mW.
The research and development of small satellites has continued to expand over the last decades. However, the propulsion systems with adequate performance have persisted to be a great challenge. In this paper, the effects of three different heaters on the specific impulse and overall thrust efficiency of a cold gas microthruster are presented. They consisted of a conventional, printed resistive thick-film element, a freely suspended wire, and a stripline split-ring resonator microplasma source, and were integrated in a single device made from the high-temperature co-fired ceramics. The devices were evaluated in two setups, where the first measured thrust and the other measured shock cell geometry. In addition, the resistive elements were evaluated as gas temperature sensors. The microplasma source was found to provide the greatest improvement in both specific impulse and thrust efficiency, increasing the former from an un-heated level of 44–56 s when heating with a power of 1.1 W. This corresponded to a thrust efficiency of 55%, which could be compared with the results from the wire and printed heaters which were 51s and 18%, and 45s and 14%, respectively. The combined results also showed that imaging the shock cells of a plasma heated thruster was a simple and effective way to determine its performance, when compared to the traditional thrust balance method.
A high-pressure peristaltic membrane micropump, which is capable of pumping against a back pressure of 150 bar, has been evaluated. The main focus was to maintain the flow characteristics also at high back pressures. The pump was manufactured by fusion bonding of parylene-coated stainless-steel stencils. A large-volume expansion connected to the solid-to-liquid phase transition in paraffin was used to move 10 µm stainless-steel membranes. The pump was evaluated by using two different driving schemes, a four-phase cycle and a six-phase cycle. With the six-phase cycle, a constant flow rate of 0.4 µL min-1 was achieved over an interval ranging from atmospheric pressure to 130 bar. At lower back pressures, the more energy efficient four-phase cycle achieved slightly higher flow rates than the six-phase cycle. However, it required higher driving voltage at high back pressures. Since the pump is thermally activated, a temperature sensor was integrated to control the melting and solidification of paraffin, implying capability of increasing the performance of the pump. With a thickness of only 1 mm as well as a simple and robust design, the micropump is well suited for integration in analytical systems. The high pressures managed are in the region needed for, e.g., high-performance liquid chromatography systems.
Substrate integrated waveguides (SIWs) are presented and demonstrated in a flexible printed circuit board (flex PCB) for application in the 77-81 GHz range. The vertical walls of the SIWs presented in this paper consist of multiple electrodeposited metallic wires. The diameters of these wires and the spacing between them are on the order of hundreds of nanometers. Hence, the walls can be seen as continuous metallic walls, and the leakage losses through them become negligible. In turn, the SIWs presented in this paper can operate at higher frequencies compared with previously presented structures that are realized with PCB fabrication processes. The attenuation of the SIWs is comparable to that of microstrip lines on the same sample. The SIWs are successfully demonstrated in a SIW-based slot antenna. The antenna gain along the z-axis (normal-to-plane) was found to be around 2.8 dBi at 78 GHz which is in agreement with the simulated values. [2008-0047]
A fabrication process for vertical thermopiles embedded in a 75-mu m-thick polyimide foil has been developed for flexible printed circuit boards (flex PCBs). The vertical connections consist of electrodeposited antimony- and nickel-plated through-hole vias. The plated through-hole vias consist of multiple wires, with a total metal content that is 1% of the total via volume. The via fabrication technique is similar to standard flex PCB wet etch and metallization processes. The main difference is that the foils are pretreated with ion irradiation to induce highly selective vertical etch rates. The thermopiles were characterized by measuring their voltage response to an applied temperature difference across the foil thickness.