Improving the performance of biomimetic hair-flow sensors by electrostatic spring softening

Abstract

We report improvements in the detection limit and responsivity of biomimetic hair-flow sensors by electrostatic spring softening. Applying a dc-bias voltage to our capacitive flow sensors results in a reduced sensory threshold, improving the mechanical transfer and flow detection limit by more than 6 dB. We further show that the sensor's responsivity for airflows is also improved on application of high-frequency ac-bias voltages to the sensor's capacitive structures with little sensitivity to the bias frequency.

A biomimetic accelerometer inspired by the cricket's clavate hair

“…Improvement of these electronics, by reduction of its noise, will help to bring the detection threshold for the accelerometer towards the thermal noise-limited threshold. Similar differences between measured and (calculated) thermal noise levels have been observed for our previously reported biomimetic hair flow sensors [21,22].…”

“…We showed that this MEMS hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 m s 22 and a dynamic range of more than 35 dB. Further, the accelerometer has low responsivity to airflow, clear directivity and a bias instability of 5 Â 10 23 m s…”

“…A similar technique can be applied to the biomimetic accelerometer by electrostatically reducing the torsional stiffness S and could be useful for, for example, robotic applications in which adaptation to the environment is required. The technique of electrostatic spring softening (ESS) has been investigated thoroughly for our biomimetic hair-based flow sensors and can lead to an improvement in responsivity of more than 80% and a reduced sensory threshold of more than 50% in the case of noise which is dominated by, for example, electronics [22]. As the accelerometer's geometry and parameters are similar to those of the hair flow sensor, comparable results can be expected.…”

Tunable Sensor Response by Voltage-Control in Biomimetic Hair Flow Sensors

“…In addition, the resonance frequency is observed to decrease (about 20%). Overall, measurements are in good agreement with modeling and it is shown clearly that DC-biasing leads to a larger sensitivity below the sensor's resonance frequency ( Figure 6) [1]. …”

“…Despite the fact that we show the benefits of such schemes for our flow-sensors only, the two-port models used are far more generic and suggest suitability of these schemes in a much broader range of applications. With this in mind we have put the results of these three schemes in this one overview but do not claim new results relatively to earlier reported studies, notably references [1][2][3].…”