Bioinspired Low-Angle-Dependent Photonic Crystal Elastomer for Highly Sensitive Visual Strain Sensor.

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Photonic crystals (PCs) exhibit unique photonic band gap properties applicable to sensors and smart displays.
• Nonclose-packed (NCP) structures and high refractive index (RI) contrast are crucial for PC sensor sensitivity during mechanical stress.

Purpose of the Study:

• To develop a novel, highly sensitive, and robust photonic crystal strain sensor using a unique fabrication strategy.
• To enable naked-eye detection of applied force through visible structural color changes.

Main Methods:

• Fabrication of an NCP-structured PC with high RI using a coating-etching strategy.
• Utilizing a flexible 3D cross-linked polymer network for elasticity and robustness.
• Characterization of mechanochromic sensitivity and optical properties.

Main Results:

• Achieved high mechanochromic sensitivity (∼8.3 nm/%) and a substantial reflection peak shift (Δλ = 249 nm).
• Demonstrated isotropic optical properties with a broad viewing angle due to high RI contrast (Δn = 0.43).
• The sensor visually indicates applied force strength through structural color changes.

Conclusions:

• A novel fabrication strategy for sensitive PC strain sensors was successfully developed.
• The sensor's high sensitivity, robustness, and isotropic optical properties offer broad applicability.
• Potential applications include human movement monitoring and secure message encryption.