Physicists re-create nature's best sound system

Scientists hope a new sensory system that mimics that of the wood cricket will improve severe hearing problems in humans.

Scientists have re-created the highly sensory hairs of crickets, a development that could lead to next-generation implants for the hearing-impaired.

Physicists at the Netherlands-based University of Twente have built artificial hairs like those found on the chirping insects, whose highly evolved sound detection helps avoid predators like spiders or wasps, according to research published this week in the Journal of Micromechanics and Microengineering.

"These sensors are the first step towards a variety of exciting applications as well as further scientific exploration," Marcel Dijkstra, a member of the Twente team, said in a statement. "We could use them to visualize airflow on surfaces, such as an aircraft fuselage."

Cricket hairs are fine-tuned to detect airflow with energies as small as--or even below--thermal noise levels, according to the research. With the natural defense, grounded crickets like the wood cricket Nemobius sylvestris can perceive changes in the air current caused by the beating of another insect's wing, for example.

Each tiny hair sits in a socket on a cricket's appendages, called cerci, and can be directed independently of others. Airflow causes the hair to rotate in its socket, which in turn fires a neuron. This allows the cricket to detect low-level sound in any direction and use the collective information of sensors to act, according to the research.

Scientists have managed to produce a few hundred mechanical hairs that are longer than normal cricket hairs, which can measure 1 millimeter. The sensors are composed of thin layers of electrically insulating and conducting materials to form structured electrodes on a suspended membrane. The hairs, made of a photo-structurable polymer, are placed on the membrane.

The goal of the experiment is to create comparable sensory systems using Micro-Electro-Mechanical Systems (MEMS) technology--which is the integration of mechanical elements, sensors, actuators and electronics on a common chip. These chips could ultimately be used in hearing aids.

Dijkstra said that because the sensors are small and consume little energy, they can also be applied to large sensor networks.

The research is part of the European Union project CICADA (Cricket Inspired perCeption and Autonomous Decision Automata), a project to study and mimic biological concepts through technology.

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