Acceleration Sensor Compares Unfavorably With a Bees Mechanoreceptors

Mechanoreceptors detect distortions of the bee's body by monitoring the bending of cuticle. Distortions occur from brushing against objects, the bending of appendages during walking and flying, and from vibrations transmitted through the air. Mechanoreceptors contain hairs that attach to nerve cells. When the hairs bend, action potentials from the nerve cells inform the nervous system about positions of body parts and rates of change of these bending movements. Bees and other insects also possess campaniform sensilla. These organs are found in areas of their body surface that are subject to stress. Sensilla are projections of thin cuticle raised into thin domes about five to thirty micrometers across. Deformation of the domes activates neurons.

In contrast, one manufactured acceleration sensor is a chip and sensor electronics contained within a DIL40 silicon housing. To build this sensor, one embeds oxygen atoms in silicon and then 'dopes' a monocrystalline epitaxial layer several mm thick on the silicon. A cap sensor in this surface having its 'sensitive axis' parallel to the surface of the chip is held near electrodes suspended on small silicon beams. Moving or accelerating the device increases the capacitance between a fixed and a moveable electrode, so capacitance increases on one side of the device and decreases on the other side. Each capacitor reads out separately to give a differential measurement. Circuits on a second chip sense the differential capacity and convert it to a voltage that is proportional to the acceleration. Acceleration sensors are used now in auto crash detection, controlling vehicular dynamics and for measuring shock.

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