Development of a shear measurement sensor for measuring forces at human-machine interfaces

Area of Science:

• Biomechanics
• Biomedical Engineering
• Medical Device Development

Background:

• Shear force measurement is critical for pressure ulcer research and treatment.
• Existing methods may lack the precision or applicability for complex interfaces.
• Understanding forces on human-machine interfaces is key to preventing tissue damage.

Purpose of the Study:

• To introduce and validate a novel bi-axial shear transducer for measuring shear forces.
• To assess the sensor's accuracy, precision, and reliability.
• To measure shear forces experienced at the human-wheelchair interface.

Main Methods:

• Developed a bi-axial shear sensor using strain gauges integrated into layered aluminum and polyvinyl chloride plates.
• Validated the sensor's performance using standard weights, assessing range, sensitivity, linearity, crosstalk, and variation.
• Deployed an array of 24 shear sensors within mats to measure interface forces during sitting and standing movements in a wheelchair.

Main Results:

• The shear sensor demonstrated high accuracy and precision with a measurement range of -50 to 50 N and sensitivity of 0.3 N.
• Excellent linearity (R(2)=0.9625) and minimal crosstalk error (0.635% ± 0.031%) were observed.
• Significantly higher shear forces were recorded on the sacrum and ischium (15.5 N) compared to other areas (3.5 N average) during posture changes.

Conclusions:

• The developed shear sensor is a reliable and accurate tool for quantifying shear forces.
• The findings highlight critical high-force areas (sacrum, ischium) during wheelchair use.
• This technology offers potential for improved understanding and prevention of pressure ulcers.