Precise, high-energy focused electron beams can improve polymer strength

Advancements in fabrication technologies have revolutionized the field of materials science. In recent years, innovative materials for applications in electrical, energy storage, and catalysis have been developed. Among novel materials, polymers such as polyethylene (PE) are remarkable for their chemical inertness, lightweight nature, and flexibility. However, PE is increasingly susceptible to crack initiation and propagation—a process where a micro-crack forms and spreads across the material surface when exposed to high stress—limiting its widespread use.

Scientists around the globe have employed crazing, a phenomenon where micro-voids and fibrils are intentionally introduced into a material to improve the structural and mechanical properties of polymers. Several reports indicate that crazing can enhance the material properties of polymers while also preventing crack initiation and propagation. However, one major drawback limiting the use of conventional approaches to crazing is the lack of controllability.

In this light, a research team comprising Postdoctoral Fellow Dr. Sirorat Toocharoen and Professor Masayuki Shimojo, both from the Department of Materials Science and Engineering, Shibaura Institute of Technology, Japan, has utilized focused electron beam (FEB) irradiation to precisely control crazing in PE polymer. Additionally, they investigated the irradiation parameters that affect crazing and verified whether FEB irradiation can arrest crack propagation. Their research findings were published online in the journal Advanced Materials Technologies on 24 July 2025.

Explaining the motivation behind the present study, Dr. Toocharoen says, “It is well-known that polymers are inherently sensitive to electron beam exposure, even during conventional imaging techniques such as scanning electron microscopy (SEM). However, FEB irradiation has the ability to induce structural changes at micro- to nanoscale levels with high spatial precision. This realization led us to explore how FEB could be utilized not only as a diagnostic tool but also as a method for purposeful structural modification in polymers.”

Initially, the researchers observed structural changes in the PE polymer following FEB irradiation. SEM analysis further confirmed the presence of nanovoids and nanofibrils in PE, which were characteristic of crazing. Thereafter, they evaluated the effects of irradiation parameters such as accelerating voltage, beam current, and irradiation time on crazing. Through Monte Carlo simulations, they found that high-to-moderate energy FEB beams were ideal for inducing craze formation in deeper areas of PE, while lower-energy beams caused crazing close to the surface.

To further validate if crazing could arrest crack propagation, the scientists introduced pre-cracks into PE, followed by exposure to FEB irradiation. Post-irradiation tensile strength analysis revealed that the pre-crack widened considerably in non-irradiated PE. Remarkably, PE irradiated with FEB showed minimal crack opening and prevented crack propagation.

“The ability to precisely induce crazing and control crack-arrest behavior in PE demonstrates the strong potential of FEB for future applications,” comments Dr. Toocharoen. “Our findings are particularly relevant for industries requiring lightweight, flexible, and mechanically reliable polymer components in compact forms, such as flexible electronics, biomedical devices, aerospace, and micro/nanoelectromechanical systems. Moreover, this study provides valuable insights for nano-fabrication processes and is important for guiding further in-depth research in this area.”

In summary, this study demonstrates the advantages of using FEB irradiation for modifying the structural and mechanical properties of polymers. By enabling the precise control of inducing micro-voids and fibrils, FEB can fuel the development of innovative materials with superior material properties.

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Reference
DOI: 10.1002/admt.202501197

About Shibaura Institute of Technology (SIT), Japan
Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained “learning through practice” as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and had received support from the ministry for 10 years starting from the 2014 academic year. Its motto, “Nurturing engineers who learn from society and contribute to society,” reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 9,500 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.

Website: https://www.shibaura-it.ac.jp/en/

About Postdoctoral Fellow Sirorat Toocharoen from SIT, Japan
Dr. Sirorat Toocharoen is currently a Postdoctoral Fellow in the Department of Materials Science and Engineering at Shibaura Institute of Technology, Japan, where she has been a member of Professor Masayuki Shimojo’s laboratory since her doctoral studies. Her current research focuses on material characterization, nanotechnology, and the use of focused electron beam (FEB) irradiation for polymer and material modification. She has published several research papers in peer-reviewed journals on materials science and FEB-based nanomodification.