Real-Time Plasmonic Strain Sensors Based on Surface Relief Diffraction Gratings.

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Azobenzene thin films enable surface relief grating fabrication.
• Flexible polymer substrates like PDMS are crucial for wearable and adaptable devices.
• Strain sensing requires materials with predictable and measurable responses to deformation.

Purpose of the Study:

• To fabricate and characterize large-scale diffraction gratings on flexible PDMS substrates for strain sensing applications.
• To evaluate the performance of these gratings using multiple analytical techniques, including surface plasmon resonance (SPR).
• To determine the suitability of these novel strain sensors for real-world applications.

Main Methods:

• Fabrication of surface relief gratings on azobenzene thin films.
• Transfer of gratings to flexible PDMS substrates via soft lift-off lithography.
• Analysis of strained PDMS gratings using diffraction angle measurements, Atomic Force Microscopy (AFM), and SPR spectroscopy.

Main Results:

• All measurement methods demonstrated a linear strain response, confirming sensor usability.
• SPR-based sensing showed increasing pitch and decreasing modulation depth with applied strain.
• SPR peak shift of ~1.0 nm/%, and intensity decrease of ~0.3 a.u./% strain were observed.
• PDMS gratings maintained integrity through multiple stretching and relaxation cycles.

Conclusions:

• The developed PDMS gratings are effective and reliable strain sensors.
• The linear response and durability make them suitable for practical, real-world applications.
• SPR spectroscopy provides quantitative data for strain monitoring with these flexible gratings.