Tri-axial plantar pressure sensor: design, calibration and characterization

Area of Science:

• Biomechanics
• Biomedical Engineering
• Sensor Technology

Background:

• Accurate measurement of plantar pressure is crucial for understanding foot biomechanics and diagnosing conditions.
• Existing sensors often lack the ability to simultaneously measure vertical and shear forces, limiting comprehensive gait analysis.

Purpose of the Study:

• To develop and characterize a novel tri-axial plantar pressure sensor capable of measuring vertical and shear forces.
• To assess the sensor's performance metrics, including sensitivity, non-linearity, and hysteresis.
• To lay the groundwork for a plantar pressure measurement platform for clinical applications.

Main Methods:

• A novel tri-axial sensor design incorporating a central post, four parallel plates, and a miniature pressure transducer (MPT).
• Capacitive sensing technology employed for measuring anterior-posterior and medial-lateral shear pressures.
• Simultaneous measurement of vertical plantar pressure using a commercial MPT.
• Characterization of sensor performance including force ranges (0-15 N shear, 0-28 MPa vertical), sensitivity, non-linearity, and hysteresis.

Main Results:

• The tri-axial sensor successfully measures both vertical and shear plantar pressures simultaneously.
• The shear component exhibits a sensitivity of 1.3 mV/g, with 8.3% non-linearity and 7.3% hysteresis.
• The commercial MPT for vertical pressure shows high accuracy with 0.094% non-linearity and 0.567% hysteresis.
• Individual sensors can measure shear forces up to 15 N and vertical pressures up to 28 MPa.

Conclusions:

• A novel tri-axial plantar pressure sensor has been successfully developed and characterized.
• The sensor's ability to measure vertical and shear forces offers a significant advancement in plantar pressure analysis.
• The developed technology holds promise for creating advanced plantar pressure platforms for gait analysis in clinical settings.