Development and validation of a 3D-printed interfacial stress sensor for prosthetic applications

Area of Science:

• Biomedical Engineering
• Rehabilitation Technology
• Sensor Technology

Background:

• Mechanical stresses at the stump-socket interface are critical for prosthetic socket comfort and efficacy.
• Current monitoring methods may lack the ability to simultaneously measure both pressure and shear stresses.
• Tissue breakdown due to improper socket fit is a significant concern for lower-limb amputees.

Purpose of the Study:

• To develop and validate a novel capacitance-based sensor for simultaneous measurement of pressure and shear stresses.
• To assess the sensor's performance, including its range, linearity, and resolution.
• To explore the potential clinical applications of the sensor in evaluating prosthetic socket fitting and preventing stump tissue breakdown.

Main Methods:

• Fabrication of a flexible capacitance sensor using rapid prototyping technology.
• Analysis of sensor performance using finite element analysis (FEA).
• Electromechanical testing to evaluate pressure and shear stress monitoring capabilities.
• Development of a post-signal processing model for signal separation.

Main Results:

• The sensor successfully monitored pressure and shear stresses up to 350 kPa and 80 kPa, respectively.
• Demonstrated high linearity (5-8%) and excellent stress resolution (pressure: ~1.3 kPa, shear: ~0.6 kPa).
• Effective separation of pressure and shear signals was achieved, beneficial for calibration.

Conclusions:

• The developed capacitance sensor offers a low-cost, versatile solution for monitoring stump-socket interface stresses.
• It has the potential to improve prosthetic socket fitting evaluation in clinical settings.
• The sensor can alert amputees to excessive loading, aiding in the prevention of stump tissue breakdown.