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Development of capacitive pure bending strain sensor for wireless spinal fusion monitoring

Lin, Ji-Tzuoh and Walsh, Kevin W. and Jackson, Douglas and Aebersold, Julia and Crain, Mark and Naber, John F. and Hnat, William P. (2007) Development of capacitive pure bending strain sensor for wireless spinal fusion monitoring. Sensors and Actuators A: Physical, 138 (2). 276 - 287.

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A MEMS (microelectromechanical system) capacitive-based pure bending strain sensor is presented for use in spinal fusion monitoring. The sensor is designed to interface with a telemetry system that does not require a battery and contained in a housing that is attached to spinal fusion rods. The cantilever structure of the sensor is composed of two parallel plates with a narrow gap and a conjoint end. Nine permutations of the design with different metal coverage areas (14 mm2, 9.3 mm2 and 4.7 mm2) and gaps (3 μm, 6 μm and 7.4 μm) were examined. The nominal capacitance ranges from 7.6 pF to 42 pF. The capacitance changes 31.4–65.1% for a strain range of 0–1000 μ depending on the design parameters. An analytical model is developed for the sensor mounted to a cantilever test bar and compared to experimental results of actual devices. The model and experimental results show an average difference of 5% for all nine designs investigated. The final sensor design achieved a linear gauge factor of 252 and was fabricated for the spinal fusion application.

Item Type:Article
Uncontrolled Keywords:Bending strain sensor; Capacitive; Cantilever structure; Microelectromechanical system (MEMS); Spinal fusion monitoring
Subjects:Analytical Science > Nanotechnology for sensing and actuating
ID Code:4860
Deposited By:SPI
Deposited On:24 Apr 2009 17:55
Last Modified:07 Oct 2010 10:05

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