Micro-strain sensing using wrinkled stiff thin films on soft substrates as tunable optical grating.

Area of Science:

• Materials Science
• Optical Engineering
• Strain Measurement

Background:

• Optical gratings are crucial for various sensing applications.
• Poly (dimethylsiloxane) (PDMS) offers unique properties for fabricating flexible optical components.
• Understanding thermal expansion is vital for material selection and performance prediction.

Purpose of the Study:

• To develop and validate a novel strain sensing approach using wrinkled PDMS as an optical grating.
• To investigate the mechanism of strain sensing based on PDMS grating periodicity changes.
• To determine the coefficient of thermal expansion (CTE) of different materials using this method.

Main Methods:

• Fabrication of wrinkled PDMS patterns to serve as optical gratings.
• Bonding PDMS gratings onto substrates (e.g., copper, silicon).
• Inducing thermal strain and measuring changes in the diffraction angle of the PDMS grating.

Main Results:

• The wrinkled PDMS grating effectively functions as an optical sensor for thermally-induced strain.
• The change in grating periodicity directly correlates with the applied thermal strain.
• Measured CTE values for copper and silicon substrates closely matched established reference values.

Conclusions:

• The proposed PDMS-based optical grating is a viable method for strain sensing.
• This technique enables accurate determination of material CTE through thermal strain analysis.
• The approach offers a promising tool for material characterization and thermal stress evaluation.