MEMS fluxgate magnetometer for parallel robot application

An advanced real-time workspace monitoring for parallel kinematic machines including tasks like self-calibration and exception handling demands integrated sensors measuring the angular position of the robot joints. This work introduces a single-axis MEMS fluxgate magnetometer developed for the specified application. The sensor is composed of high aspect ratio helical coils with generating and sensing functions around an electrodeposited nickel–iron core featuring ferromagnetic behavior. The core is designed in racetrack geometry causing an excellent directional sensitivity of the sensor for measuring the magnetic orientation of permanent magnets which rotate on the joint shaft. This approach allows the real-time detection of the required joint angle and the simplified analytical solution of direct kinematics.     

Effect of physical vapor deposition metallic thin films on micro injection molded weld line mechanical properties

Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. But the unfavorable and unavoidable defect of weld line in micro injection molding part leads to detrimental mechanical and surface properties. The possibility of the functional thin film for enhancing micro injection molded weld lines was investigated. Two typical coating materials (aluminum and titanium) with various film thicknesses (400, 600, 800 nm) were deposited on one side of the micro injection molded weld line tensile sample via physical vapor deposition (PVD) method. The coated micro weld line samples were characterized by tensile tests. The results show that PVD films of aluminum and titanium can reinforce the strength and stiffness of micro injection molded weld line, even at thin thickness levels. But when the film thickness is increasing, the weaker adhesion between metallic films and polymers decreased the PVD films’ enhancing performance for micro weld line mechanical properties due to the degradation of polymers related to longer time exposure under high temperature.     

Novel 3D manufacturing method combining microelectrial discharge machining and electrochemical polishing

This paper reports on the potential of microelectrical discharge machining (μEDM) as an innovative method for the fabrication of 3D microdevices. To demonstrate the wide capabilities of μEDM two different microsystems—a microfluidic device for the dispersion of nanoparticles and a star probe for microcoordinate metrology—are presented. To gain optimized process conditions as well as a high surface quality an adequate adaption of the single erosion parameters such as energy, pulse frequency and spark gap has to be carried out and is discussed below. Thus, a surface roughness of R_a?=?80?nm is achieved at the channel bottom. The fabricated stylus elements for the star probe have sphere diameters of 40–200?μm. For further surface quality enhancement a subsequent electrochemical polishing step is investigated. In case of the dispersion micromodule a combined process chain of μEDM-milling and electropolishing has reached a surface improvement above 70%.     

Micro gear pump with internal electromagnetic drive

This paper presents the concept, design and fabrication of a gear pump based on recently introduced synchronous micro motors as an integrated driving system. The micro motor is fully integrated in the fluidic system consisting of the inlet, outlet and pump chamber. A preliminary test on the gear pump flow rate is successfully reported. The whole system is mainly realized by means of micro fabrication technologies like UV-depth lithography and copper electroplating. Polymer magnets with alternating axial magnetization were applied in the toothed rotors. The use of polymer magnets affords a miniaturization with maximum space filling and without limitation in shape. In first tests the temperature behavior and the functional capability were investigated.     

Reduced percolation concentration in polypropylene/expanded graphite composites: Effect of viscosity and polypyrrole

With the goal to obtain material combining electrical and thermal conductivity at low filler loadings, composites based on polypropylenes (PP) and expanded graphite (EG) have been prepared. The effects of matrix viscosity and of coating the EG particles with polypyrrole (PPy, EG/PPy = 37.5/62.5 by weight) on the EG dispersibility and formation of percolation structures have been analyzed. When increasing the EG amount from 6 to 8 wt %, the electrical conductivity of PP/EG composites increased by 7–9 orders of magnitude, independent of matrix viscosity. When EG‐PPy is added, percolation was observed between 8 and 12 wt % EG‐PPy (3 and 4.5 wt % EG) in case of PP with higher viscosity and 6 wt % EG (2.25 wt % EG) in case of PP with lower viscosity, exhibiting a strong synergistic effect of EG and PPy in the latter case. In contrast, PPy does not contribute to reduction of thermal percolation concentration. Thermal percolation is observed at 8 wt % EG in PP/EG composites, but no percolation was found in PP/EG‐PPy composites with EG‐PPy contents of up to 20 wt %, corresponding to 7.5 wt % EG. Analyzing the melt rheology it becomes clear that the contribution of PPy to the formation of a filler network is strongly dependent on the matrix viscosity. The comparison of thermal, electrical and rheological percolation reveals that PPy participates in electron transport reducing the electrical percolation but not to heat transport. Overall, we found a good correlation between electrical, thermal, and melt rheological percolation concentrations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41994.     

Dual photonic-electrochemical lab on a chip for online simultaneous absorbance and amperometric measurements

A dual lab on a chip (DLOC) approach that enables simultaneous optical and electrochemical detection working in a continuous flow regime is presented. Both detection modes are integrated for the first time into a single detection volume and operate simultaneously with no evidence of cross-talk. The electrochemical cell was characterized amperometrically by measuring the current in ferrocyanide solutions at +0.4 V vs gold pseudoreference electrode, at a flow rate of 200 μL min(-1). The experimental results for ferrocyanide concentrations ranging from 0.005 to 2 mM were in good agreement with the values predicted by the Levich equation for a microelectrode inside a rectangular channel, with a sensitivity of 2.059 ± 0.004 μA mM(-1) and a limit of detection (LoD) of (2.303 ± 0.004) × 10(-3) mM. Besides, optical detection was evaluated by measuring the absorbance of ferricyanide solutions at 420 nm. The results obtained therein coincide with those predicted by the Beer-Lambert law for a range of ferricyanide concentrations from 0.005 to 0.3 mM and showed an estimated LoD of (0.553 ± 0.001) × 10(-3) mM. The DLOC was finally applied to the analysis of L-lactate via a bienzymatic reaction involving lactate oxidase (LOX) and horseradish peroxidase (HRP). Here, the consumption of the reagent of the reaction (ferrocyanide) was continuously monitored by amperometry whereas the product of the reaction (ferricyanide) was recorded by absorbance. The DLOC presented good performance in terms of sensitivity and limit of detection, comparable to other fluidic systems found in the literature. Additionally, the ability to simultaneously quantify enzymatic reagent consumption and product generation confers the DLOC a self-verifying capability which in turn enhances its robustness and reliability.     

Batch fabrication of micro grippers with integrated actuators

In this paper we present improvements in the field of batch fabricated micro grippers with shape memory alloy (SMA) actuators or pneumatic drives. In this context we illustrate two methods of structuring SMA foils. Moreover, it is shown how the processed SMA elements can be embedded into monolithic SU-8 grippers. We also describe actuator elements for silicon/SU-8 hybrid micro grippers. Furthermore, we report on the advantages of pneumatic micro grippers and how this alternative actuation principle can be fabricated in batch technology. In this regard, a thermoplastic adhesive electrodepositing process is presented.     

A multifunction and bidirectional valve-less rectification micropump based on bifurcation geometry

In this paper, we introduce a novel valve-less rectification micropump based on bifurcation geometry. Three micropumps based on three different bifurcation configurations were designed, fabricated and experimentally investigated. These designs demonstrate the potentials of developing bidirectional micropumps and multifunction microfluidic devices (combined functions of micro pumping and mixing). Polydimethylsiloxane (PDMS) was employed to fabricate the micropumps. Circular piezoelectric transducers (PZT) were used as flow actuators. Detailed fabrication procedures are illustrated. The micropumps were tested against two ranges of actuator frequencies. The first test was conducted in a frequency range between 0 and 100 Hz with small increments of 5 Hz, while the second test was conducted in a frequency range between 0 and 300 Hz with increments of 50 Hz. Ethanol was used as the working fluid in all experiments. A new dimensionless parameter was introduced to evaluate the efficiency of valve-less rectification micropumps and determine the optimum operational frequency. The flow rate and maximum back pressure were measured. Results of experiments confirmed and demonstrated the feasibility of valve-less rectification micropumps based on bifurcation geometry at a low frequency range. Additionally, results showed the potentials of multifunctional, bidirectional, and self-priming micropumps.