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(SCI) TURKISH RESEARCHERS DEVELOP METAMATERIAL-BASED STRAIN SENSORS.

ANKARA, Jul 23, 2009 (TUR) -- Turkish researchers developed metamaterial-based strain sensors that are highly sensitive to mechanical deformation.

Rohat Melik, a doctorate student at the Bilkent University, researchers Emre Unal and Nihan Kosku Pekgoz carried out studies under the chairmanship of Associate Professor Hilmi Volkan Demir, a lecturer at the Bilkent University Electric and Electronic Engineering Department in Ankara, and developed "bio-implantable passive sensors."

These sensors help assessment of bone fractures, and this research is the first of its type in the world.

A giant U.S. firm is willing to use this technology in its new-generation implants.

"One out of ten bone fractures does not heal properly due to improper load distribution and strain profiles during the healing process," Demir told AA correspondent.

Demir said that to provide implantable tools for the assessment of bone fractures, they had designed novel, bio-implantable, passive, on-chip, RF-MEMS strain sensors that relied on the resonance frequency shift with mechanical deformation.

"For this purpose, we modeled, fabricated and experimentally characterized two on-chip sensors with high quality factors for in vivo implantation," he said.

According to information Demir gave, one of the sensors has an area of ~0.12 mm2 with a quality factor of ~60 and the other has an area of ~0.07 mm2 with a quality factor of ~70.

To monitor the mechanical deformation by measuring the change in the resonance frequencies with the applied load, the team employed a controllable, point load applying experimental setup designed and constructed for in vitro characterization. In the case of the sensor with the larger area, when the team apply a load of 3920 N, they obtain a frequency shift of ~330 MHz and a quality factor of ~76. For the smaller sensor, the frequency shift and the quality factor are increased to 360 MHz and 95, respectively. These data demonstrate that our sensor chips have the capacity to withstand relatively high physiologic loads, and that the concomitant and very large resonant frequency shift with the applied load is achieved while maintaining a high signal quality factor. These experiments demonstrate that these novel sensors have the capacity for producing high sensitivity strain readout, even when the total device area is considerably small. Also, the team have demonstrated that our bio-implantable, passive sensors deliver a telemetric, real-time readout of the strain on a chip. Placing two more resonators on the sides of the sensor to serve as transmitter and receiver antennas, we achieved to transfer contactless power and read out loads in the absence of direct wiring to the sensor. With this model, where telemetric measurements become simpler due to the fact that all sensor system is built on the same chip, the team obtain a frequency shift of ~190 MHz with an increase in the quality factor from ~38 to ~46 when a load of 3920 N is applied. Therefore, as a first proof of concept, the team have demonstrated the feasibility of our on-chip strain sensors for monitoring the mechanical deformation using telemetry-based systems.

The research was published in an international magazine "Applied Physics Letters."

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Publication:Anadolu (Eskisehir, Turkey)
Date:Jul 23, 2009
Words:514
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