Unidirectional Electron-Tunnelling Flexible PDMS Strain Sensor with Aligned Carbon Nanotubes.

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Piezoresistive polymers are created by incorporating carbon nanotubes (CNTs) into polymer matrices.
• Achieving directional sensitivity and reducing cross-sensitivity in CNT-polymer composites requires aligning the CNTs.

Purpose of the Study:

• To present and characterize the alignment of CNTs within polydimethylsiloxane (PDMS).
• To investigate the resulting strain sensor performance and the influence of alignment parameters.
• To model the sensor behavior, including electron-tunnelling effects.

Main Methods:

• Alignment of high-aspect-ratio CNTs within PDMS using electric fields.
• Characterization of CNT alignment using various field strengths, frequencies, and times.
• Fabrication and testing of strain sensors based on aligned CNT-PDMS.
• Development of analytical and numerical models to understand sensor behavior and alignment dynamics.

Main Results:

• Demonstrated a two-phase piezoresistive response in aligned CNT-PDMS strain sensors.
• Achieved high gauge factors (k ≈ 4500) in the preferential alignment direction due to electron-tunnelling.
• Observed low gauge factors (k ≈ 22) in the orthogonal direction, indicating effective unidirectionality.
• Confirmed sensor dynamic stability under cyclic strain with initial drifts stabilizing over cycles.

Conclusions:

• CNT alignment in PDMS is a viable method for creating high-performance, unidirectional strain sensors.
• Electron-tunnelling significantly contributes to the enhanced piezoresistive response in the preferential direction.
• The developed models provide valuable insights for optimizing alignment processes and sensor design.