Eddy current-tunneling magneto-resistive sensor for micromotion detection of a tibial orthopaedic implant

Rajas P. Khokle*, Fernando Franco, Susana Cardoso de Freitas, Karu P. Esselle, Michael C. Heimlich, Desmond J. Bokor

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Citation (Scopus)


In this paper, an eddy current loop coupled with the tunneling magneto resistor (EC-TMR) is used as a displacement sensor to detect the micromotion of an orthopaedic implant. The high sensitivity and signal to noise ratio of the TMR sensor are used to achieve high resolution at a large standoff distance. First, a small three-turn rectangular eddy current loop of dimension 2.5 mm × 10 mm is designed and simulated inside the human body using a full-wave EM simulator. Then, it is fabricated and tested using vector network analyzer. The magnetic tunnel junction stack is optimized and a six-element TMR sensor is fabricated and characterized. The eddy current and tunnelling magneto resistive sensor are integrated and heterodyne detection technique is used to obtain the high-resolution micromotion detection at an extended standoff range. This technique can be used for in-vivo detection of the micromotion of the orthopaedic implant which will be useful in reducing the revision surgeries due to the mechanical failures of the implant.

Original languageEnglish
Pages (from-to)1285-1292
Number of pages8
JournalIEEE Sensors Journal
Issue number4
Publication statusPublished - 15 Feb 2019



  • Eddy current sensor
  • Micromotion
  • Orthopedic implants
  • TMR sensor

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