Highly-sensitive, biomimetic hair sensor arrays for sensing low-frequency air flows (original) (raw)
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Learning from crickets: artificial hair-sensor array developments
2010 IEEE Sensors, 2010
We have successfully developed biomimetic flowsensitive hair-sensor arrays taking inspiration from mechanosensory hairs of crickets. Our current generation of sensors achieves sub mm/s threshold air-flow sensitivity for single hairs operating in a bandwidth of a few hundred Hz and is the result of a few iterations in which the natural system (i.e. crickets filiform hair based mechano-sensors) have shown ample guidance to optimization. Important clues with respect to mechanical design, aerodynamics, viscous coupling effects and canopy based signal processing have been used during the course of our research. It is only by consideration of all these effects that we now may start thinking of systems performing a "flow-camera" function as found in nature in a variety of species.
Hair-Based Flow-Sensing Inspired by the Cricket Cercal System
World scientific series in nanoscience and nanotechnology, 2014
micro electro mechanical system (MEMS) offers exciting possibilities for the fabri cation of bioinspired mechanosen sors. Over the last years we have been working on cricket inspired hair-sen sor arrays for spatio-temporal flow-field observations (i.e., flow-cameras) and source locali zation. Whereas making Aow-sensors as energy efficient as cricket hair-sensors appears to be a real challenge, we have managed to fabricate hair-sensors with sub-millimeter per second flow sensing thresholds, use them in lateral line experiments, address them individually while in arrays, track transient flows, quantify viscous coupling effects and use parametric effects to achieve sharp filtering and amplification. In this research insect biologists and engineers have been working in close collaboration, generating a bidirectional flow of inforrnation and knowiedge, beneficial to both. For example where the engineer ing has greatly benefitted from the insights derived from biology and biophysical modeis, the biologists have taken advantage of MEMS structures allowing for experiments that are hard to do on living material.
Hair sensors for oscillatory airflow, operating in the regime of bulk flow, particle velocity or both, can be characterized by several methods. In this work, we discuss harmonic measurements on MEMS hair flow sensors. To characterize this type of flow sensor the use of three different types of oscillatory airflow source is investigated. A loudspeaker, a vibrating sphere and a standing wave tube all have specific characteristics regarding their acoustic field, frequency range, maximum velocity amplitude and the possibility to chose the ratio between pressure and flow velocity. They are compared and an overview is given with respect to which source is the most appropriate under specific conditions. Furthermore, by combining information from the flow setups used new insights into sensor operation can be gained.
Interfacing of differential-capacitive biomimetic hair flow-sensors for optimal sensitivity
Biologically inspired sensor-designs are investigated as a possible path to surpass the performance of more traditionally engineered designs. Inspired by crickets, artificial hair sensors have shown the ability to detect minute flow signals. This paper addresses developments in the design, fabrication, interfacing and characterization of biomimetic hair flow-sensors towards sensitive high-density arrays. Improvement of the electrode design of the hair sensors has resulted in a reduction of the smallest hair movements that can be measured. In comparison to the arrayed hairs-sensor design, the detection-limit was arguably improved at least twelve-fold, down to 1 mm s -1 airflow amplitude at 250 Hz as measured in a bandwidth of 3 kHz. The directivity pattern closely resembles a figure-of-eight. These sensitive hair-sensors open possibilities for high-resolution spatio-temporal flow pattern observations.
MEMS based hair flow-sensors as model systems for acoustic perception studies
Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors, allowing for capacitive read-out. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplification) and their susceptibility to noise (stochastic resonance).
Advancements in Biomimetic Hair Flow-Sensor Arrays
2011
In this paper we present the latest developments in the design, fabrication and application of single and arrays of biomimetic hair flow-sensors towards high-resolution air-flow imaging. Redesigning the electrode system of the hair sensor (using SOI wafer technology) has led to improve the detection limit down to 1 mm/s air-flow amplitude using 3 kHz measurement bandwidth. SOI technology facilitates the fabrication of waferscale arrays, which can be interrogated individually using a smart array interfacing scheme e.g Frequency Division Multiplexing (FDM). The combination of high-sensitive hair sensors and FDM opens possibilities for high spatial-resolution air-flow measurements. A chip-scale single hairs array is used to demonstrate flow-pattern measurements by reconstructing the field of a dipole projected at its position. The separation distance between array elements is determined using the reconstructed dipole field.
Proceedings of IEEE Sensors, 2010
This paper addresses the latest developments in biomimetic hair-flow sensors towards sensitive high-density arrays. Improving the electrodes design of the hair sensor, using Silicon-on-Insulator (SOI) wafer technology, has resulted in the ability to measure small capacitance changes as caused by minute rotations of single-hair sensors. The detection limit, as measured in a bandwidth of 3 kHz, was about 1 mm/s air-flow amplitude, an enhancement of 52% in comparison to the previous hair-sensor array design. The directivity pattern was improved now closely resembling a figure of eight. These sensors open possibilities for high-resolution flow pattern observations. I.
Performance assessment of bio-inspired systems: flow sensing MEMS hairs
Bioinspiration & Biomimetics, 2014
Despite vigorous growth in biomimetic design, the performance of man-made devices relative to their natural templates is still seldom quantified, a procedure which would however significantly increase the rigour of the biomimetic approach. We applied the ubiquitous engineering concept of a figure of merit (FoM) to MEMS flow sensors inspired by cricket filiform hairs. A well known mechanical model of a hair is refined and tailored to this task. Five criteria of varying importance in the biological and engineering fields are computed: responsivity, power transfer, power efficiency, response time and detection threshold. We selected the metrics response time and detection threshold for building the FoM to capture the performance in a single number. Crickets outperform actual MEMS on all criteria for a large range of flow frequencies. Our approach enables us to propose several improvements for MEMS hair-sensor design.
Crickets as Bio-Inspiration for MEMS-Based Flow-Sensing
Flow Sensing in Air and Water, 2014
MEMS offers exciting possibilities for the fabrication of bio-inspired mechanosensors. Over the last few years, we have been working on cricketinspired hair-sensor arrays for spatio-temporal flow-field observations (i.e. flow camera) and source localisation. Whereas making flow-sensors as energy efficient as cricket hair-sensors appears to be a real challenge we have managed to fabricate capacitively interrogated sensors with sub-millimeter per second flow sensing thresholds, to use them in lateral line experiments, address them individually while in arrays, track transient flows, and use non-linear effects to achieve parametric filtering and amplification. In this research, insect biologists and engineers have been working in close collaboration, generating a bidirectional flow of information and knowledge, beneficial to both, for example, where the engineering has greatly benefitted from the insights derived from biology and biophysical models, the biologists have taken advantage of MEMS structures allowing for experiments that are hard to do on living material.
Artificial sensory hairs based on the flow sensitive receptor hairs of crickets
This paper presents the modelling, design, fabrication and characterization of flow sensors based on the wind-receptor hairs of crickets. Cricket sensory hairs are highly sensitive to drag-forces exerted on the hair shaft. Artificial sensory hairs have been realized in SU-8 on suspended Si x N y membranes. The movement of the membranes is detected capacitively. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept.