Thermal noise estimation in bio-inspired hair flow sensor

In micromachining technology, the reduction in the size of the moving structures has many advantages in different applications. However, these moving structures are subjected to mechanical noise resulting from the molecule agitation. In this abstract, we investigate the thermal-mechanical noise in our artificial hair-flow sensor. The realization of such sensors with high sensitivities requires designs with both low thermal-mechanical noise and high-resolution of angular displacement

Modal fields calculation using the finite difference beam propagation method

A method is described to construct modal fields for an arbitrary one- or two-dimensional refractive index structure. An arbitrary starting field is propagated along a complex axis using the slowly varying envelope approximation (SVEA). By choosing suitable values for the step-size, one mode is maximally increased in amplitude on propagating, until convergence has been obtained. For the calculation of the next mode, the mode just found is filtered out, and the procedure starts again. The method is tested for one-dimensional refractive index structures, both for nonabsorbing and for absorbing structures, and is shown to give fast convergenc

Optimisation of a two-wire thermal sensor for flow and sound measurements

The Microflown is an acoustic sensor measuring particle velocity instead of pressure, which is usually measured by conventional microphones. In this paper an analytical model is presented to describe the physical processes that govern the behaviour of the sensor and determine its sensitivity. The Microflown consists of two heaters that act simultaneously as sensors. Forced convection by an acoustic wave leads to a small perturbation of this temperature profile, resulting in a temperature difference between the two sensors. This temperature difference, to which the sensitivity is proportional, is calculated with perturbation theory. Consequently the frequency dependent behaviour of the sensitivity is analysed; it is found that there are two important corner frequencies, the first related to the time constant velocity of heat diffusion between the sensors, the second related to the heat capacity of the heaters. The developed model is verified by experiments. Previously a very good model has been given for the performance of the Microflown in a channel, i.e. with both heaters between fixed walls walls in the positive and negative z-direction. Here, a model is presented that describes the situation of the present used sensors: without walls under and above them. Model predictions are compared to experimental result

Artificial lateral-line system for imaging dipole sources using Beamforming techniques

AbstractIn nature, fish have the ability to localize prey, school, navigate, etc. using the lateral-line organ [1]. Here we present the use of biomimetic artificial hair-based flow-sensors arranged as lateral-line system in combination with beamforming techniques for dipole source localization in air. Modelling and measurement results show the artificial lateral-line ability to image the position of dipole sources accurately. Such systems open possibilities for flow-based near-field environment mapping which can be beneficial e.g. to robot guidance applications

Nanometer range closed-loop control of a stepper micro-motor for data storage

We present a nanometer range, closed-loop control study for MEMS stepper actuators. Although generically applicable to other types of stepper motors, the control design presented here was particularly intended for one dimensional shuffle actuators fabricated by surface micromachining technology. The stepper actuator features 50 nm or smaller step sizes. It can deliver forces up to 5 mN (measured) and has a typical range of about 20 μm. The target application is probe storage, where positioning accuracies of about 10 nm are required. The presence of inherent actuator stiction, load disturbances, and other effects make physical modeling and control studies necessary. Performed experiments include measurements with openand closed-loop control, where a positioning accuracy in the order of tens of nm or better is obtained from image data of a conventional fire-wire camera at 30 fps

Design and realization of a miniature capacitive silicon force sensor for loads up to 500 kg

In this paper, a micromachined silicon load cell (force sensor) is presented for measuring loads up to 500 kg. The load cell has been realized and tested. Measurement results show a hysteresis error of ±0.02 % of full-scale. Creep at 500 kg after 30 minutes is within 0.01 %. These measurements show that the performance has improved by a factor of 10 compared to the previous design

Dipole source localisation using bio-mimetic flow-sensor arrays

AbstractFlow sensor arrays can be used to extract spatio-temporal flow signatures rather than average or local flow quantities. We look at the equivalent of a fish lateral-line sensor array in air and assess the ability of our artificial hairs flow-sensor arrays to detect flow velocity distributions generated by a vibrating sphere. The measured flow patterns along a virtual lateral-line, carried out over a bandwidth of 0.3 Hz, are found to be in excellent agreement with theory and are used successfully to demonstrate source-distance determination