C.M. Bruinink

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.

Engineering of biomimetic hair-flow sensor arrays dedicated to high-resolution flow field measurements

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.

Non-resonant parametric amplification in biomimetic hair flow sensors: Selective gain and tunable filtering

We demonstrate that the responsivity of flow sensors for harmonic flows can be improved significantly by non-resonant parametric amplification. Using electrostatic spring softening by AC-bias voltages, increased responsivity and sharp filtering are achieved in our biomimetic flow sensors. Tunable filtering is obtained for non-resonant electromechanical parametric amplification, applicable at a wide range of non-resonant frequencies while achieving highly selective gain of up to 20 dB.

Lowering the sensory threshold and enhancing the responsivity of biomimetic hair flow sensors by electrostatic spring softening

We report improvements in detection limit and responsivity of biomimetic hair flow sensors by electrostatic spring-softening (ESS). Applying a DC voltage to our capacitive flow sensors results in a reduced sensory threshold, which gives an improvement for the flow detection limit of more than 30%. In addition, the mechanical transfer shows large (80% and more) voltage-controlled electro-mechanical amplification of the flow signal for frequencies below the sensors resonance.