Tough and stretchable ionic polyurethane foam for use in wearable devices

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Developing robust and conductive materials is essential for advanced wearable devices.
• Traditional soft polymers like polyurethane (PU) lack conductivity, while conductive materials like carbon nanotubes (CNTs) are often brittle.
• Poor interfacial interactions in composites often hinder practical performance.

Purpose of the Study:

• To engineer a stretchable PU/CNTs composite foam for high-performance strain sensing applications.
• To enhance the mechanical properties and conductivity of PU through the incorporation of CNTs.
• To address the challenges of brittleness and poor interfacial adhesion in PU-based conductive composites.

Main Methods:

• Incorporation of a cationic chain extender to functionalize PU, improving mechanical strength (12.30 MPa tensile strength) and stretchability (>1000% breaking strain).
• Fabrication of porous PU foam using a salt-templating method.
• Loading of carboxylic CNTs (negatively charged) onto the porous PU foam to impart conductivity.
• Characterization of the composite foam's performance as a strain sensor.

Main Results:

• The developed PU/CNTs composite foam exhibits excellent mechanical properties, including high tensile strength and significant stretchability.
• The material demonstrates high sensitivity to small strains with a gauge factor (GF) of 5.2.
• Outstanding long-term cycling stability was observed, confirming its reliability for repeated use.
• The composite foam was successfully utilized for diverse motion detection applications.

Conclusions:

• The developed strategy successfully created a stretchable and conductive PU/CNTs composite foam.
• This material overcomes the inherent limitations of PU and CNTs, offering enhanced performance for wearable strain sensors.
• The findings provide valuable insights for designing efficient PU-based sensor materials for wearable technology.