MSU Technologies

Photoelastic Polymer Sensor

Executive Summary

Sensors for measuring force or pressure are used in a wide variety of applications in industrial, healthcare and automation. Soft sensors, in particular, are used in applications where only low levels of stress are measured. However, one drawback with current soft sensors, is the long term repeatability and cost. Researchers at Michigan State University and Stony Brook University have developed a new photoelastic polymer-based sensor technology. Upon stretching or compression, the sensor material changes color rapidly within seconds, which can be measured and translated into a 2-dimensional force or pressure measurement. The sensor can be used in a variety of applications such as robotics, where rapid force detection is needed and feedback critical for robot operation, or medical where the touching of tissue or transportation of organs requires extreme care.

Description of Technology

The sensor is based on a unique polymer technology that changes color when stress is applied such as when stretched or compressed. The color change is measured with a camera and directly related to this stress which is numerically translated into a 2-dimensional stress pattern using proprietary software. The system has been tested for 10,000 + cycles with consistent and accurate results over time.

Benefits

Long term fatigue resistance. Tested to over 10,000 cycles for various loading rates
Ideal mechanical and elastic properties for long-term, repetitive stress sensing
Tunable properties such as stiffness and sensitivity
Toughness up to 3000 J/m². Fatigue threshold > 400 J/m²
Sense objects with wide range of modulus spanning from ~ kPa to ~ GPa
Robust sensing performance with minimal impacts from ambient humidity