Design and Test of a New Inductive Force Sensor

Area of Science:

• Biomedical Engineering
• Orthopedics
• Sensor Technology

Background:

• Current weekly cast changes for clubfoot treatment lack strong evidence.
• Optimizing cast change intervals requires accurate measurement of foot adaptation rates.
• Existing methods may not provide the necessary precision for determining optimal treatment timing.

Purpose of the Study:

• To develop and characterize a novel force sensor for measuring adaptation in clubfeet.
• To provide data for establishing evidence-based, efficient cast change intervals in clubfoot treatment.
• To assess the sensor's suitability for long-term, in-situ force measurements.

Main Methods:

• Designed a force sensor utilizing an LC-tank circuit whose resonance frequency shifts with proximity to a metal target.
• Incorporated a thin rubber ring to convert the proximity sensor into a force sensor.
• Characterized sensor performance using static and incremental load tests, evaluating sensitivity, resolution, accuracy, and drift.

Main Results:

• The custom-made force sensor demonstrated high sensitivity (1.7±0.8×105 counts/N), resolution (0.15±0.06 mN), and accuracy (3.5±3.0 %).
• Observed sensor drift was low at (2.1±0.7) %/log10(h), outperforming other thin force sensors.
• Preliminary measurements in clubfoot and Dupuytren finger treatments indicated successful long-term force monitoring.

Conclusions:

• The developed force sensor is a viable tool for precise, long-term force measurements in orthopedic applications.
• This technology has the potential to refine clubfoot treatment protocols by enabling data-driven decisions on cast changes.
• Further research can validate the sensor's clinical utility in optimizing treatment efficacy and patient recovery.