Most accelerometers today are based on the capacitive principle. However, further miniaturization for micro integration of those sensors leads to a poorer signal-to-noise ratio due to a small total area of the capacitor plates. Thus, other transducer principles should be taken into account to develop smaller sensors. This paper presents the development and realization of a miniaturized accelerometer based on the tunneling effect, whereas its highly sensitive effect regarding the tunneling distance is used to detect small deflections in the range of sub-nm. The spring-mass-system is manufactured by a surface micro-machining foundry process. The area of the shown polysilicon (PolySi) sensor structures has a size smaller than 100 µm × 50 µm (L × W). The tunneling electrodes are placed and patterned by a focused ion beam (FIB) and gas injection system (GIS) with MeCpPtMe3 as a precursor. A dual-beam system enables maximum flexibility for post-processing of the spring-mass-system and patterning of sharp tips with radii in the range of a few nm and initial distances between the electrodes of about 30–300 nm. The use of metal–organic precursor material platinum carbon (PtC) limits the tunneling currents to about 150 pA due to the high inherent resistance. The measuring range is set to 20 g. The sensitivity of the sensor signal, which depends exponentially on the electrode distance due to the tunneling effect, ranges from 0.4 pA/g at 0 g in the sensor operational point up to 20.9 pA/g at 20 g. The acceleration-equivalent thermal noise amplitude is calculated to be 2.4–3.4 mg/. Electrostatic actuators are used to lead the electrodes in distances where direct quantum tunneling occurs.
To realize quantum tunneling applications with movable electrodes, sharp tips with radii down to several tens of nanometers are necessary. The use of a focused ion beam (FIB) and focused electron beam (FEB) with a gas injection system (GIS) allows the integration of geometries in the nanoscale directly into micro and nano systems. However, the implementation of the tunneling effect clearly depends on the material. In this work, a metal-organic precursor is used. The investigation of the prepared tunneling electrodes enables an insight into FIB/FEB parameters for the realization of quantum tunneling applications. For this purpose, a high-resolution transmission electron microscopy (HRTEM) analysis is performed. The results show a dependence of the material nanostructure regarding platinum (Pt) grain size and distribution in an amorphous carbon matrix from the used beam and the FIB currents. The integration of the tips into a polysilicon (PolySi) beam and measuring the current signal by approaching the tips show significant differences in the results. Moreover, the approach of FEB tips shows a non-contact behavior even when the tips are squeezed together. The contact behavior depends on the grain size, proportion of platinum, and the amount of amorphous carbon in the microstructure, especially at the edge area of the tips. This study shows significant differences in the nanostructure between FIB and FEB tips, particularly for the FIB tips: The higher the ion current, the greater the platinum content, the finer the grain size, and the higher the probability of a tunneling current by approaching the tips.
This paper presents two measurement setups to analyse hanging and falling droplets from different nozzles. The focus of these setups is on reducing costs and complexity of such systems compared to systems mentioned in literature which consists of an expensive high speed camera with according lens. Therefore the first setup uses an industrial camera and a corresponding lens having a resolution of up to 800 x 600 pixels and enabling the capturing of movies with more than 1000 frames per second (by using a reduced resolution). Additionally a weighing scale is implemented. The second setup represents a real low-cost approach, which nevertheless offers about 120 frames per second and a resolution of 640 × 480 pixels by using two RaspberryPi microcontrollers and the according camera modules. The cameras are placed in an angle of 90°. The presented setups are compared to each other and the advantages and disadvantages of each system are figured out. Subsequently the results of an exemplary measurement of the droplet volume are presented showing the quality of both setups with a maximum deviation of the optical results of less than ± 6 % compared to the results of the weighing scale.
Droplet dosing devices for liquid medicine are widely spread in self-medication for prevention or in the event of illness. This paper presents investigations on the often unnoticed process of bubble formation in droplet dosing devices for liquid medicine which is decisive for the whole functionality of these systems. To obtain information about this process and how it affects the dosage, drip operations with an exemplary device have been evaluated. Based on these evaluations the bubble formation is explained qualitatively. Finally a mathematical approach to predict critical changes in the bubble formation process is presented.
Existing investigations to estimate different properties of falling droplets are based on empirical data or complex mathematical approaches. This paper presents a new simple analytical approach to calculate selected properties of droplets, in particular the volume and frequency of falling droplets, out of a thin vertical cylindrical capillary. The fluid-reservoir is located above the capillary and provides a constant flow into the droplet. This leads to drop formation times less than one second. The results of the calculation are validated by numerical simulations and experiments.
The use of focused ion and focused electron beam (FIB/FEB) technology permits the fabrication of micro- and nanometer scale geometries. Therefore, FIB/FEB technology is a favorable technique for preparing TEM lamellae, nanocontacts, or nanowires and repairing electronic circuits. This work investigates FIB/FEB technology as a tool for nanotip fabrication and quantum mechanical tunneling applications at a low tunneling voltage. Using a gas injection system (GIS), the Ga-FIB and FEB technology allows both additive and subtractive fabrication of arbitrary structures. Using energy dispersive X-ray spectroscopy (EDX), resistance measurement (RM), and scanning tunneling microscope (STM)/spectroscopy (STS) methods, the tunneling suitability of the utilized metal–organic material–platinum carbon (PtC) is investigated. Thus, to create electrode tips with radii down to 15 nm, a stable and reproducible process has to be developed. The metal–organic microstructure analysis shows suitable FIB parameters for the tunneling effect at high aperture currents (260 pA, 30 kV). These are required to ensure the suitability of the electrodes for the tunneling effect by an increased platinum content (EDX), a low resistivity (RM), and a small band gap (STM). The STM application allows the imaging of highly oriented pyrolytic graphite (HOPG) layers and demonstrates the tunneling suitability of PtC electrodes based on high FIB aperture currents and a low tunneling voltage.
This paper presents the design of an extremely miniaturized accelerometer based on the tunneling effect. Because of its high sensitivity the tunneling effect allows the detection of smallest deflections. The aim of the novel design is a large geometric miniaturization at the lowest possible natural frequency with a nominal acceleration of +/−1 g corresponding to a deflection of +/−9.36 Å. The poly-silicon (PolySi) sensor structure with a size (L × W) of 98 µm × 85 µm is designed in a way that the main displacement operates just in one direction. To lead the sensor into operational conditions, control a constant distance between the tunneling electrodes and perform self-test actuations two electrodes are placed below the sensor structure. The tunneling tip is deposited by a focused ion beam (FIB) to provide the tunneling section with a third pad on the substrate. Within this paper the focus is on the functional implementation of the structure, the investigation of the electrostatic actuators and the deposition of the tunneling tip by the FIB.
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