Abstract
Due to sensor size and supporting circuitry, in-vivo load and deformation measurements are currently restricted to applications within larger orthopaedic implants. The objective of this study is to repurpose a commercially available low-power, miniature, wireless, telemetric, tire-pressure sensor (FXTH87) to measure load and deformation for future use in orthopaedic and biomedical applications. The capacitive transducer membrane was modified, and compressive deformation was applied to the transducer to determine the sensor signal value and the internal resistive force. The sensor package was embedded within a deformable enclosure to illustrate potential applications of the sensor for monitoring load. To reach the maximum output signal value, sensors required compressive deformation of 350 ± 24 µm. The output signal value of the sensor was an effective predictor of the applied load on a calibrated plastic strain member, over a range of 35 N. The FXTH87 sensor can effectively sense and transmit load-induced deformations. The sensor does not have a limit on loads it can measure, as long as deformation resulting from the applied load does not exceed 350 µm. The proposed device presents a sensitive and precise means to monitor deformation and load within small-scale, deformable enclosures.
Highlights
Instrumentation of sensor packages within orthopaedic implants has long been a challenge due to requirements related to the size of the sensor package, the need for wireless telemetry, and low-power consumption [1,2]
The results of this study show that a repurposed tire-pressure sensor may be feasible for use in orthopaedic applications, as it is capable of monitoring small-scale deformation that can be calibrated into load measurements, has minimal power consumption, and can effectively transmit through tissue
We have demonstrated that a commercially available made alternative methods of load system (MEMS) pressure sensor can be converted into an effective tool to measure deformation and load
Summary
Instrumentation of sensor packages within orthopaedic implants has long been a challenge due to requirements related to the size of the sensor package, the need for wireless telemetry, and low-power consumption [1,2]. Embedded sensors can be tasked to measure load, strain, temperature, and acceleration. These variables can allow scientists and clinicians to diagnose and monitor implant wear, implant migration, tissue infection, and other factors such as bone healing. Most sensor packages are too large to be incorporated into smaller orthopaedic components, such as fracture fixation plates, intervertebral spinal fusion cages, and high tibial osteotomy implants, to name a few. These packages are not limited by the size of the sensor itself, but by size of accompanying signal processing, wireless telemetry, and power-management aspects
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