A research group led by Prof. ZHANG Wenwu at Ningbo Institute of Materials Technology and Engineering (NIMTE) of Chinese Academy of Sciences (CAS), has achieved dynamic structural color display based on femtosecond laser variable polarization processing, in cooperation with researchers at Swinburne University of Technology (SUT) in Australia. The study was published in Adv. Mater. Interfaces.
Developed from the interactions between natural light and periodic structures, vivid structural colors are widespread in nature. Thanks to the functional advantages, such as hydrophobicity, anti-reflection, mechanical strength at light weight and bactericidal characteristics, structural colors have attracted increasing interest in the fields of information storage, material coloring and anti-counterfeiting, etc.
Femtosecond laser micro/nano surface structuring is an efficient method to induce a periodic surface structure, namely, the laser-induced periodic surface structure (LIPSS), which plays a crucial role in the formation of structural colors.
The researchers at NIMTE systematically investigated the effect of femtosecond laser polarization on the orientation of LIPSS. A half-wave plate (HWP) was introduced to rotate the orientation angle, leading to the polarization adjustment of the femtosecond laser beam.
Four types of structural units with designated periodic orientations were written on the same sample, displaying four different colorful images. The experiment and analysis indicated that vivid colors can be displayed by adjusting the observation angle, and a multi-pattern display can be realized by rotating the sample. Besides, the lithography-free inscribed patterns showed a strong azimuthal angular sensitivity to color and its brightness.
In addition to simple letters, complex patterns, such as quick response (QR) code, can be imprinted by virtue of the polarization control of the femtosecond laser pulses.
The study demonstrated that femtosecond laser variable polarization processing is an effective method to realize the display of dynamic structural colors, and may shed light on the biomimetic lithography-free processing modification of various materials.
This work was supported by 2025 major projects (Nos. 2018B10059, 2019B10074), Excellent Projects in Zhejiang Province (No. 2020C01036), the National Natural Science Foundation of China (Grant No. 51901236), the Zhejiang Postdoctoral Scientific Research Project (No. ZJ2019166), and Ningbo Natural Science Foundation (No. 2019A610168).
Fig. The QR code imprinted via the polarization control of the femtosecond laser pulses (Image by NIMTE)
Contact
WU Peichao
Ningbo Institute of Materials Technology and Engineering
E-mail: wupeichao@nimte.ac.cn