Parametrical study of miniature generators for large motion applications

Designing a generator for large amplitude motion has lead to an energy-consistent model that also considers the finite dimensions of the device. Using SPICE software we have studied the influence of several design parameters on the output of the generator, including the limited motion of the seismic mass imposed by small system dimensions. Three different types of load circuits are presented, as well as their optimization towards output voltage and power

Power extraction from ambient vibration

Autonomous devices such as sensors for personal area networks need a long battery lifetime in a small volume. The battery size can be reduced by incorporating micro-power generators based on ambient energy. This paper describes a new approach to the conversion of mechanical to electrical energy, based on charge transportation between two parallel capacitors. The polarization of the device is handled by an electret. A largesignal model was developed, allowing simulations of the behavior of any circuit based on this generator for any mechanical input signal. A small-signal model was derived in order to quantify the output power as a function of the design parameters. A layout was made based on a standard SOI-technology, available in a MPW. With this layout it is possible to generate 100 mW at 1200 Hz

An efficient hardware-optimized compression algorithm for wireless capsule endoscopy image transmission

AbstractA dedicated image compression algorithm was developed for wireless capsule endoscopy (WCE). The proposed approach reduces the amount image data without compromising the image quality. This allows an increase in image throughput to improve the real-time vision capabilities of a WCE system. The algorithm is based on a normalized Haar-wavelet transformation, aiming at a hardware-optimized implementation in a low-power FPGA or telemetry ASIC for wireless capsule endoscopes. Taking advantage of the limited color content of endoscopic images, this solution uses the YCbCr color space combined with efficient recoding of the wavelet transformation data. In this way adequate compression ratios at decent image qualities can be achieved in a hardware efficient thus low power implementation, outperforming existing hardware implemented algorithms

A distributed wearable EM field recorder for RF exposure assessment in real environments

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Silicon photonic sensors incorporated in a digital microfluidic system

Label-free biosensing with silicon nanophotonic microring resonator sensors has proven to be an excellent sensing technique for achieving high-throughput and high sensitivity, comparing favorably with other labeled and label-free sensing techniques. However, as in any biosensing platform, silicon nanophotonic microring resonator sensors require a fluidic component which allows the continuous delivery of the sample to the sensor surface. This component is typically based on microchannels in polydimethylsiloxane or other materials, which add cost and complexity to the system. The use of microdroplets in a digital microfluidic system, instead of continuous flows, is one of the recent trends in the field, where microliter- to picoliter-sized droplets are generated, transported, mixed, and split, thereby creating miniaturized reaction chambers which can be controlled individually in time and space. This avoids cross talk between samples or reagents and allows fluid plugs to be manipulated on reconfigurable paths, which cannot be achieved using the more established and more complex technology of microfluidic channels where droplets are controlled in series. It has great potential for high-throughput liquid handling, while avoiding on-chip cross-contamination. We present the integration of two miniaturized technologies: label-free silicon nanophotonic microring resonator sensors and digital microfluidics, providing an alternative to the typical microfluidic system based on microchannels. The performance of this combined system is demonstrated by performing proof-of-principle measurements of glucose, sodium chloride, and ethanol concentrations. These results show that multiplexed real-time detection and analysis, great flexibility, and portability make the combination of these technologies an ideal platform for easy and fast use in any laboratory

Low loss CMOS-compatible PECVD silicon nitride waveguides and grating couplers for blue light optogenetic applications

This paper presents silicon nitride (SixNy) photonic integrated circuits (PICs) with high performance at a wavelength of 450 nm, which, therefore, is suitable for neuronal stimulation with optogenetics. These PICs consist of straight and bent waveguides, and grating couplers that are fabricated in a complementary metal-oxide-semiconductor (CMOS)-compatible plasma enhanced chemical vapor deposition SixNy platform. Their characterization shows propagation losses of 0.96 +/- 0.4 dB/cm on average for straight waveguides that are 1-5 mu m wide and bend insertion losses as low as 0.2 dB/90. for 1 mu m wide waveguides with a radius of 100 mu m. Additionally, the grating coupler characterization shows that they can deliver about 10 mu W of light in an area of 5 x 9 mu m(2) (240 mW/mm(2)), which is captured from an uncollimated laser diode (70 mW). Besides delivering sufficient power for optogenetic applications, the gratings have dimensions that are comparable to the size of a neuron, which would allow single cell interaction. These results demonstrate that, with this SixNy platform, high-density and large-scale implantable neural devices can be fabricated and readily integrated into existing CMOS-compatible neuro-electronic platforms

On-body calibration and measurements using a personal, distributed exposimeter for wireless fidelity

This paper describes the design, calibration, and measurements with a personal, distributed exposimeter (PDE) for the on-body detection of radio frequency (RF) electromagnetic fields due to Wireless Fidelity (WiFi) networks. Numerical simulations show that using a combination of two RF nodes placed on the front and back of the body reduces the 50% prediction interval (PI50) on the incident free-space electric-field strength E-RMS(free). Median reductions of 10 dB and 9.1 dB are obtained compared to the PI50 of a single antenna placed on the body using a weighted arithmetic and geometric average, respectively. Therefore, a simple PDE topology based on two nodes, which are deployed on opposite sides of the human torso, is applied for calibration and measurements. The PDE is constructed using flexible, dual-polarized textile antennas and wearable electronics, which communicate wirelessly with a Universal Serial Bus (USB) connected receiver and can be unobtrusively integrated into a garment. The calibration of the PDE in an anechoic chamber proves that the PI50 of the measured E-RMS(free) is reduced to 3.2 dB. To demonstrate the real-life usability of the wireless device, a subject was equipped with the PDE during a walk in the city of Ghent, Belgium. Using a sample frequency of 2 Hz, an average incident power density of 59 nW m(-2) was registered in the WiFi frequency band during this walk

Minimization of Ionic Transport Resistance in Porous Monoliths for Application in Integrated Solar Water Splitting Devices

Monolithic solar water splitting devices consist of photovoltaic materials integrated with electrocatalysts and produce solar hydrogen by water splitting upon solar illumination in one device. Upscaling of monolithic solar water splitting devices is obstructed by high ohmic losses in the electrolyte due to long ionic transport distances. A new design overcomes the problem by introducing micron sized pores in a silicon wafer substrate coated with electrocatalysts. A porous solar hydrogen device was simulated by applying a current corresponding to ca. 10% solar-to-hydrogen efficiency. Porous monoliths of 550 µm thickness with varying pore size and spacing were fabricated by laser ablation and electrochemically characterized. Ohmic losses well below 100 mV were reached at 14.4% porosity with 77 µm pores spaced 250 µm apart in 0.25 M KOH electrolyte. In 1 M KOH, 100 mV was reached at 6% porosity with 1 mm pore spacing. Our results suggest ohmic losses below 50 mV can be achieved when using 10 µm thick substrates at 0.2% porosity. These findings make it possible for monolithic solar water splitting devices to be scaled without loss of efficiency