Optimization of Cricket-inspired, Biomimetic Artificial Hair Sensors for Flow Sensing

High density arrays of artificial hair sensors, biomimicking the extremely sensitive mechanoreceptive filiform hairs found on cerci of crickets have been fabricated successfully. We assess the sensitivity of these artificial sensors and present a scheme for further optimization addressing the deteriorating effects of stress in the structures. We show that, by removing a portion of chromium electrodes close to the torsional beams, the upward lift at the edges of the membrane due to the stress, will decrease hence increase the sensitivity.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Biomimetic flow-sensor arrays based on the filiform hairs on the cerci of crickets

In this paper we report on the latest developments in biomimetic flow-sensors based on the flow sensitive mechano-sensors of crickets. Crickets have one form of acoustic sensing evolved in the form of mechanoreceptive sensory hairs. These filiform hairs are highly perceptive to low-frequency sound with energy sensitivities close to thermal threshold. Arrays of artificial hair sensors have been fabricated using a surface micromachining technology to form suspended silicon nitride membranes and double-layer SU-8 processing to form 1 mm long hairs. Previously, we have shown that these hairs are sensitive to low-frequency sound, using a laser vibrometer setup to detect the movements of the nitride membranes. We have now realized readout electronics to detect the movements capacitively, using electrodes integrated on the membranes

Optimization Of Bio-inspired Hair Sensor Arrays

Crickets use a pair of hairy appendages on their abdomen called cerci, each of which contains numerous mechano-receptive filiform hairs. These sensitive hairs can respond even to the slightest air movements, down to 0.03 mm/s, generated by the approaching predators and initiating an escape mechanism in the crickets. Bio-mimicking the cricket cerci, arrays of artificial hair sensors have been successfully fabricated using advanced MEMS techniques. Despite its appreciable performance, the actual cricket filiform hairs outperform artificial hair sensors by several orders in sensitivity. Nevertheless, more careful look at the anatomy and physiology of the cricket cerci provides new directions to be explored with MEMS technologies to realize higher sensitivities on a par with crickets’. This paper aims to provide an overview of comparisons between the actual and artificial hair sensors in terms of sensitivity, structural functionalities and robustness and draws out constructive insights to optimize sensor performance

Fabrication of an active nanostencil with integrated microshutters

An active nanostencil, consisting of a thin (200 nm) silicon nitride membrane with attached polysilicon microactuators that can be used to dynamically open and/or close holes in the silicon nitride membrane, is presented. This nanostencil can be used as a shadow mask in an evaporation setup. Main features of the nanostencil are the absence of sacrificial oxide in the final product, strengthening of the membrane by a polysilicon hexagonal structure that is attached directly to the membrane and the use of low-doped regions in the polysilicon to separate the stator and rotor electrically

Micromachined capacitive long-range displacement sensor

First measurement results are presented for a surface-micromachined long-range (50– 100 μm) periodic capacitive position sensor. The sensor consists of two periodic geometries (period = 10 μm) sliding along each other with minimum spacing of about 1.5 μm. The relative displacement between the two, results in a periodic change in capacitance. An electrostatic comb-drive actuator is employed to generate displacements. Measured maximum capacitance change ΔC=0.72 fF corresponds to simulation results but needs better shielding from external noise sources. The results show this sensorconcept can potentially lead towards long-range nano-positioning control of microactuator systems

Micromachined capacitive displacement sensor for long-range nano-positioning

Integrated long-range position sensing with high accuracy will be of paramount importance for high-potential applications in a.o. future probe-based datastorage and microscopy applications [1], provided that nm position accuracy can be obtained over a range of tens of micrometers or more. This work presents the design, fabrication and measurements for an integrated incremental capacitive long-range position sensor for nano-positioning of microactuators. For compactness, economical viability and optimal performance, the aim has been to fully integrate sensor and actuator through micromachining technology, without additional micro-assembly. Two related concepts are presented and evaluated through analysis, 2D-Finite-Element Simulations and experimental assessment. The sensors consist of two periodic geometries (period ≈ 8-16μm) on resp. a slider, movable in x-direction, and sense-structures, movable in y-direction, at both sides of the slider, Fig. 1. In ICMM the displacement of the slider is measured by measuring the periodic change in capacitance ΔCs(x) with a charge-amplifier and synchronous detection technique [2]. Using sense-actuators, the gap-distance between sense-structures and slider is made smaller than is possible with standard available photo-lithography (< 2 μm), thus increasing the capacitance and the S-N Ratio

Cascading nonlinearities in an organic single crystal core fiber: The Cerenkov regime

The large nonlinear phase shifts imparted to the fundamental beam during Cerenkov second harmonic generation (SHG) in a DAN, 4-(N,N-dimethylamino)-3-acetamidonitrobenzene, single crystal core fiber are explained and modelled numerically. Cascading upconversion and downconversion processes leads to nonlinear phase shifts produced by the second order nonlinear coupling of the guided fundamental mode and the component of the Cerenkov second harmonic field trapped in the fiber cladding

Air-flow sensitive hairs: boundary layers in oscillatory flows around arthropod appendages

The aim of this work is to characterize the boundary layer over small appendages in insects in longitudinal and transverse oscillatory flows. The problem of immediate interest is the early warning system in crickets perceiving flying predators using air-flow-sensitive hairs on cerci, two long appendages at their rear. We studied both types of oscillatory flows around small cylinders using stroboscopic micro-particle image velocimetry as a function of flow velocity and frequency. Theoretical predictions are well fulfilled for both longitudinal and transverse flows. Transverse flow leads to higher velocities than longitudinal flow in the boundary layer over a large range of angles between flow and cylinder. The strong spatial heterogeneity of flow velocities around filiform-shaped appendages is a rich source of information for different flow-sensing animals. Our results suggest that crickets could perceive the direction of incoming danger by having air-flow-sensitive hairs positioned around their entire cerci. Implications for biomimetic flow-sensing MEMS are also presented