Simulation studies of parametric amplification in bio-inspired flow sensors

In this paper the effect of parametric amplification in MEMS-based air-flow hairsensors is studied. With an AC-voltage controlled torsional stiffness the rotation of the hair can be influenced. With the appropriate amplitude, phase and frequency, the rotation of the torsional hair system is increased with respect to the case without parametric amplification. Therefore, parametric amplification is identified as a method to improve the performance of MEMS-based hair air flow sensors

Parametric amplification and stochastic resonance in bio-inspired hair flow sensors

Inspired by crickets and its perception for flow phenomena, artificial hair flow sensors have been developed successfully in our group. The realization of array structures and improvement of fabrication methodologies have led to better performance, making it possible to detect and measure flow velocities in the range of sub-mm/s. To improve the performance of these artificial hair flow sensors even further, we will make use of non-linear effects. In nature a wide range of such effects exist (filtering, parametric amplification, etc.) and can give a rise\ud in sensitivity, dynamic range and selectivity. Here, we propose to use parametric amplification and stochastic resonance to improve our flow sensor performance

Highly sensitive micro coriolis mass flow sensor

We have realized a micromachined micro Coriolis mass flow sensor consisting of a silicon nitride resonant tube of 40 ?m diameter and 1.2 μm wall thickness. Actuation of the sensor in resonance mode is achieved by Lorentz forces. First measurements with both gas and liquid flow have demonstrated a resolution in the order of 10 milligram per hour. The sensor can simultaneously be used as a density sensor

A bio-inspired hair-based acceleration sensor

Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU- 8 lithography. Measu- rements show that this MEMS hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 m/s2 and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations

Nonexistence of certain edge-girth-regular graphs

Edge-girth-regular graphs (abbreviated as \emph{egr} graphs) are regular graphs in which every edge is contained in the same number of shortest cycles. We prove that there is no $3$-regular \emph{egr} graph with girth $7$ such that every edge is on exactly $6$ shortest cycles, and there is no $3$-regular \emph{egr} graph with girth $8$ such that every edge is on exactly $14$ shortest cycles. This was conjectured by Goedgebeur and Jooken. A few other unresolved cases are settled as well.Comment: 17 pages, 4 figure

On the Use of Various Oscillatory Air Flow Fields for Characterization of Biomimetic Hair Flow Sensors

To determine the characteristics of flow sensors, a suitable source for flow generation is required. We discuss three different sources for oscillating air flow, by considering their acoustic impedance, frequency range, velocity and ability to distinguish between flow and pressure. We discuss the impact of these sources on characterization of our biomimetic hair flow sensors, which operate at flow velocities from 1–100 mm/s within a frequency range from 10–1000 Hz

Micro Coriolis mass flow censor with extended range for a monopropellant micro propulsion system

We have designed and realised a micromachined micro Coriolis flow sensor for the measurement of hydrazine (N2H4, High Purity Grade) propellant flow in micro chemical propulsion systems. The sensor should be able to measure mass flow up to 6 mg/s for a single thruster or up to 24 mg/s for four thrusters. The sensor will first be used for measurement and characterisation of the micro thruster system in a simulated space vacuum environment. Integration of the sensor chip within the micro thruster flight hardware will be considered at a later stage. The new chip has an increased flow range because of an integrated on-chip bypass channel. First measurement results have demonstrated an increase in flow range which corresponds well to the designed bypass ratio

Tunable sensor response by voltage-control in biomimetic hair flow sensors

We present an overview of improvements in detection limit and responsivity of our biomimetic hair flow sensors by electrostatic spring-softening (ESS). Applying a DC-bias voltage to our capacitive flow sensors improves the responsively by up to 80% for flow signals at frequencies below the sensor’s resonance. Application of frequency matched AC-bias voltages allows for tunable filtering and selective gain up to 20 dB. Furthermore, the quality and fidelity of low frequency flow measurements can be improved using a non frequency-matched AC-bias voltage, resulting in a flow detection limit down to 5 mm/s at low (30 Hz) frequencies. The merits and applicability of the three methods are discussed

An improved bound on the chromatic number of the Pancake graphs

In this paper an improved bound on the chromatic number of the Pancake graph $P_n, n\geqslant 2$, is presented. The bound is obtained using a subadditivity property of the chromatic number of the Pancake graph. We also investigate an equitable coloring of $P_n$. An equitable $(n-1)$-coloring based on efficient dominating sets is given and optimal equitable $4$-colorings are considered for small $n$. It is conjectured that the chromatic number of $P_n$ coincides with its equitable chromatic number for any $n\geqslant 2$

Gravity gradiometer system for Earth Exploration

We develop a gravity gradiometer (GG) for use on planetary missions to planets like Mars and Jupiter. With some modifications this development is extended to include (airborne) applications for the Dutch exploratory industry. We adapt key technology of the space based GG for the use in an environment with considerable acceleration noise. The major benefit is the considerable decrease in weight and size with the presently used gradiometer systems