SCIENCE CHINA Materials, Volume 63 , Issue 7 : 1300-1309(2020) https://doi.org/10.1007/s40843-020-1351-3

Micro/nano processing of natural silk fibers with near-field enhanced ultrafast laser

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  • ReceivedFeb 29, 2020
  • AcceptedApr 12, 2020
  • PublishedApr 30, 2020


Silkworm silk fiber is an attractive material owing to its remarkable mechanical characteristics, excellent optical properties, and good biocompatibility and biodegradability. However, nano-processing of the silk fiber is still a challenge limiting its applications in nanoengineering and related fields. Herein, we report localized near-field enhancement-assisted ablation with an ultrafast laser to break this bottleneck. Localized processing of silk fiber, including nano-holing, nano-grooving, and cutting could retain the key molecular structure building blocks and the pristine functionality of the silk fiber. An extremely narrow nanohole with a width of ~64 nm was successfully achieved. The processed silk fiber can be used to transfer micro/nanoparticles and drugs, showing potential for biomedical engineering. The processing strategy developed in this study can also be extended to other materials, paving a new way for fabricating functional nanostructures with precisely controlled size and morphology.

Funded by

We acknowledge the support from the National Key R&D Program of China(2017YFB1104300,2016YFA0200103,2018YFB1107200)

the National Program for the Support of Top-notch Young Professionals

and the National Natural Science Foundation of China(51775303)


We thank Maosheng Chai, Shuang Li, and Dr. Han Li for the help with experimental tests. We thank Dr. Baihui Liang, Dr. Taotao Sun, Dr. Hengqian Hu, and Dr. Chuang Li for the experimental assistance and discussions. We acknowledge the support from the National Key R&D Program of China (2017YFB1104300, 2016YFA0200103 and 2018YFB1107200), the National Program for the Support of Top-notch Young Professionals, and the National Natural Science Foundation of China (51775303).

Interest statement

The authors declare no conflict of interest.

Contributions statement

Qiao M and Wang H contributed equally to this work. Yan J and Zhang Y supervised the project. Qiao M contributed to the nano-processing of silk fibers, mechanism analysis, and simulations. Wang H and Qiao M conducted the characterization of SEM. Wang H contributed to the AFM characterization, Raman measurements, XPS analysis, and microparticle transfer experiment. Lu H performed the mechanical measurements. Li S prepared the degummed silk fibers. Qu L, Jiang L and Lu Y guided the theoretical analysis part. Wang H, Qiao M, Yan J and Zhang Y co-wrote the paper with feedback from all authors.

Author information

Ming Qiao received his master’s degree in mechanical engineering from the University of Chinese Academy of Sciences in 2015. He is currently a PhD candidate at the Department of Mechanical Engineering, Tsinghua University. His research interests focus on femtosecond laser and micro/nano fabrication.

Huimin Wang received his BSc degree in inorganic nonmetallic material engineering from Jilin University in 2016. He is currently a PhD candidate at the Department of Chemistry, Tsinghua University, China. His current research interest focuses on nanocarbon, silk, and their hybrid materials and their applications in flexible electronics.

Jianfeng Yan received his PhD from the Department of Mechanical Engineering, Tsinghua University in 2013. He is currently an associate professor, Department of Mechanical Engineering, Tsinghua University. His research interests are mainly focused on ultrafast laser and micro/nano fabrication.

Yingying Zhang received her PhD degree in physical chemistry from Peking University in 2007. From June 2008 to June 2011, she worked at Los Alamos National Laboratory (USA) as a postdoctoral research associate. Then, she joined Tsinghua University as an associate professor in July of 2011. Her research focuses on the design and controlled preparation of nanocarbon, silk, and their hybrid materials, aiming to develop high-performance flexible electronics and wearable systems.


Supplementary information

Experimental details and supporting data are available in the online version of the paper.


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  • Figure 1

    Two different modes for the processing of silk fiber using an ultrafast laser. (a) Schematic of Mode 1 for far-field laser ablation. (b) Schematic of Mode 2 for localized near-field enhancement-assisted ablation. (c) Surface morphology of a silk fiber. (d) A simulation model of the surface wavy structures and corresponding FDTD results of the optical intensity distribution.

  • Figure 2

    Controlled hole drilling on individual silk fiber by femtosecond laser pulses with different pulse energy fluences. (a) Schematic diagram of drilling holes on a silk fiber using a femtosecond laser. (b) SEM images of the holes drilled by 500 femtosecond laser pulses with different energy fluences. (c) The measured and calculated widths of the holes ablated with different pulse energy fluences. (d) Ultraviolet-visible-infrared absorbance and transmittance spectra of silk fibers in the range of 185–1,000 nm. (e) Spatial distribution of laser intensity and corresponding free electron density. (f, g) Calculated optical intensity distributions when the laser was focused on the fiber with holes drilled by 3.84 and 7.33 J cm−2 femtosecond laser pulses, respectively.

  • Figure 3

    Characterization of laser-processed silk fibers. (a) Raman spectra of the silk fibers at different ablation sites and the spectrum of native silk fiber. (b) Survey XPS spectra of silk fabric before and after ablation with a femtosecond laser. The existing of a Si 2p peak in the full XPS survey spectrum is attributed to a silicon wafer used as a substrate. (c) High-resolution XPS C1s spectrum of silk after ablation with a femtosecond laser (top) and the spectrum of native silkworm silk (bottom). (d) Stress-strain curves of degummed silk fibers after processing using femtosecond lasers with fluences of 2.64 and 5.27 J cm−2, along with that of the native silk. The stress was computed by assuming a constant silk diameter. (e) Comparison of the toughness and Young’s modulus of processed silk and native silk. The error bars indicate standard deviations from seven different samples in each case.

  • Figure 4

    Biocompatible carrier and patterning on silk fabric. (a) A silk fiber as a biocompatible carrier after laser processing. Schematic diagram of the transfer of a PS microsphere into the hole on the silk fiber, (i) perforating individual silk fiber using the femtosecond laser, (ii) a PS microsphere at the tip of the probe, and (iii) a PS microsphere in the hole on the silk fiber. (b) Experimental optical images of the transfer of a PS microsphere into the hole on the silk fiber, (i) a hole on silk fiber, (ii) a PS microsphere at the tip of the probe, and (iii) a PS microsphere in the hole on the silk fiber. (c) The logo of Tsinghua University was patterned on to the silk fabric using the femtosecond laser. There is a coin of ten cents on the right of the silk fabric. (d) The optical microscopy image of the logo of Tsinghua University. (e, f) Optical microscopy images at different amplifications corresponding to the square area shown in (d) showing the ablation of the silk after processing with the femtosecond laser.

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