Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Fabrication of bionics Mems hair sensors

Despite the advancement of mankind in many areas of technology it is still challenging for engineered systems to compete with biological systems. For example: the auditory capabilities of bats to perceive their environment, locate prey and navigate at high velocities through complex surrounding (e.g. leafed brushes and trees) has no manmade equivalent.

Likewise the sensitivity of hair-based auditory mechano-sensors, found on e.g. crickets, to detect acoustic signals at thermal noise levels is astounding. It is this kind of performance that raises interest in biological systems and forms an invitation to critically reassess engineered systems with the purpose to see how biology can form an inspiration for manmade systems: e.g. biomimetics.

Within the IST-2001-34718 CICADA project workpackage 4 was concerned with the fabrication of flow-sensing electro-mechanical elements by silicon micro-machining technology (MEMS) and the integration of many of these sensors into arrays. Here the challenges were specifically in a) choosing and implementing proper sensing principles, b) assembling a proper processing sequence that allows for integration of long hair-like structures with thin minute sensor structures and c) optimising all parts of the sensors and sensor-arrays to achieve sufficient sensitivity. In designing and fabrication the input from other work packages is used to form optimum topologies.

In the CICADA project we have successfully fabricated artificial hair-sensors and hair-sensor arrays. These sensors are based on drag-force mediated rotations of membranes resolved by capacitive measurements. The devices were the first in literature reported sensors of this kind to show acoustic sensitivities. Although a comparison of the artificial sensors with those of crickets is delicate we approximate that our reported sensors (with hair-length of 470µm) are a factor of 10^4-10^5 less sensitive than those of crickets.

However, improvements in mechanical design (lower suspension stiffness), improved electronics and the use of the longer hairs we expect to be able to improve the sensitivity by a factor of 10^3-10^4 in the future.

The technology developed in this project allows for future developments addressing:
1) spatio-temporal flow and sound measurements,
2) adaptive control of sensitivities,
3) extension to sensors operating in fluids,
4) use of mechanical filtering (e.g. like in the mammalian cochlea) and
5) beneficial use of noise (stochastic resonance).

We are happy that the EU has shown a willingness to fund this type of research in the successor project Cilia (Customised Intelligent Lifelike Arrays) in which we will address some of the points listed above.

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University of Twente, MESA+ Research Institute
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