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This paper introduces a micro-hydrogen generator with self-circulation and self-regulation mechanisms for delivering alkaline sodium borohydride solution without parasitic power consumption. The self-circulation of the sodium borohydride solution was achieved by using directional growth and selective venting of hydrogen bubbles in microchannels, which leads to agitation and addition of fresh solution...
We report experimental results on a magnetoelectric nanoscale magnetic field generator demonstrating electrical control of the local magnetization. The magnetic field generator contains a patterned magnetoelectric layered structure (i.e. Ni-nanobar/PZT-film). An electric field applied to the PZT-film is used to control the metastable spin-structure evolution process (i.e. motion of spins, transformation...
A fully autonomous chemical gas sensor system is presented. This system is based on the exploitation of dissipated power at individual nanowires by Joule effect due to the bias current applied in conductometric measurements (self-heating), which enables heating the tiny mass of these wires up to the optimum temperatures for gas sensing applications. This novel approach only requires few miliwatts...
This paper describes a contactless RF MEMS switch, composed of two surface-micromachined tunable capacitors and two bonded-wire inductors, which can achieve a power isolation ratio of 10 dB with a capacitance variation of mere 4:1 over a narrow bandwidth near 2.4 GHz. This novel approach of using inductors eases the deflection requirement for the deformable bridge for the variable capacitor, and allows...
A nitric oxide (NO) electrochemical sensor for hypoxic, tumor cell culture applications is developed. Qualitative analysis of the electrode has been studied by cyclic voltammetry. NO amperometric measurement methods have been extensively analyzed. Square wave voltammetry method is found to be one of the optimal methods for the measurement of NO in cell cultures. A hypoxic tumor cell culture measurement...
This paper presents a micro capacitive humidity sensor based on polyimide nano-grass with improved performance such as quick response and high sensitivity. These benefits come from the modification of polyimide surface morphology and dielectric constant. The nano-grass structure is created with plasma treatment on a polyimide layer to drastically enhance the water adsorption due to the increased surface...
We show several applications for a unique method for creating user-friendly, micropatterned substrates for neuron and cell culture. With neurons, we demonstrated that our micropatterns can separate cell bodies and axons while organizing them in orderly arrays for easy experimentation. These micropatterned neuron cultures also persisted for weeks, enabling maturation and development of presynaptic...
This paper presents a simple blood plasma extraction device without any external driving force for point-of-care diagnosis. On the basis of capillary phenomenon and size exclusion, blood plasma was extracted through a planar crossflow filter using a surfactant-added poly(dimethyl siloxane)(PDMS) and SU8-based microstructure. The wetting property of PDMS was modified by mixing PDMS with nonionic surfactant,...
This paper describes a miniaturized oxygen sensor array integrated with heaters and temperature sensors and a LabVIEW-based measurement system which exactly can measure a cellular respiration level in a solution containing cells simultaneously. The designed oxygen sensor consists of Clark-type sensors, heaters, and temperature sensors of 2 times 3 array type on the substrate. 18 mum PDMS was used...
A new platform for manipulation and separation of oil-in-water emulsion droplets by using optically induced dielectrophoresis (ODEP) is reported. By utilizing different scanning speeds of a moving light beam, the oil-in-water emulsion droplets can be moved and separated with a high separation resolution. Several new applications such as pre-separation and fine separation of emulsion droplets were...
This paper presents the fabrication and operation of an integrated nano-electrospray thruster consisting of an array of microfabricated silicon capillary emitters and microfabricated silicon extractor electrodes. Based on previous work in which we showed operation of single microfabricated capillaries, the improved thruster presented here allows simultaneously operation of arrays of emitters. In addition,...
We have demonstrated the ability to increase fluid flow rates in microchannels using magnetic nanoparticles that are suspended in the fluid. A magnetic circuit was fabricated to generate a magnetic field gradient and results showed that for |nablaB| ~ 3 T/m, the fluid velocity near the channel edge increased 30 mum/sec. At |nablaB| ~ 5 T/m, the fluid velocity increased 10 - 80 mum/sec from near the...
We present a photosensitive polymer composite with superparamagnetic characteristics for the fabrication of microactuators. A uniform distribution of particles in the photosensitive polymer matrix SU-8 is achieved by applying superparamagnetic nanoparticles with the aid of a surfactant. The composite contains Fe3O4 nanoparticles up to 3 vol.% (12 wt.%) with diameters of around 13 nm. Superparamagnetic...
We have previously reported a new class of MEMS resonators based on the piezoresistive readout principle and extensional vibration mode. Those devices suffer from unwanted mode-coupling at large vibration amplitudes, giving rise to problems such as beat patterns in the time signal. In this paper, we present a novel type of piezoresistive resonator that has a shape of a ring and operates in a flexural...
In this paper we present a generalized model for predicting the electromechanical behavior of longitudinal mechanical resonators including the effect of fringing fields on the excitation of spurious flexural modes. We demonstrate the validity and pertinence of our approach by applying our model to the prediction of the vibration amplitudes of square plate resonators. Measured amplitude spectra were...
In this paper we present a high temperature stable, capacitive RF MEMS switch based on a tungsten-titanium alloy. The evaluation of the temperature stability was done by annealing experiments up to 500degC. Due to an intrinsic residual stress the switch features a large out of plane deflection. This allows the combination of high open-state isolation with a moderate pull-in voltage and with high restoring...
A frequency detector at X-band based on MEMS technology is presented, which is based on detecting the phase shift between the two different CPW transmission lines. The phase shift, which is proportional to the frequency of the signal, results in the variation of the output power. The variation is detected with two kinds of the microwave power sensors, one is the capacitive power sensor and the other...
We have developed a silicon microfabricated PEM fuel cell which uses hydrogen as fuel. The device employs flow channels with dual structure: isotropic plasma etching has been used for defining the large channels and gas conduits, and anisotropic plasma etching under passivating conditions (high concentration of oxygen in SF6) has been used to create silicon nanograss (black silicon) to increase surface...
Quality factors as high as 362,768 have been measured for 61-MHz polysilicon wine-glass disk micromechanical resonators operated at cryogenic temperatures down to 5K. The measured results not only represent a ~2.5times increase in Q over the room temperature value, equivalent to a nearly 10-dB improvement in phase noise; but also provide some limited insight into the intrinsic material damping and...
A drug-delivery microdevice integrating pH-responsive nano-hydrogel composite membranes functioning as intelligent nano valves is described. The polymeric microdevices are monolithic without requiring peripheral control hardware or additional components for controlling drug-release rates. pH-responsive nanoparticles were synthesized and embedded into a composite membrane. The resulting pH-responsive...
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