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When materials are engineered on a nanoscale—just a few atoms thick—thermal energy at room temperature can instigate structural undulations. These fluctuations can significantly impact the mechanical characteristics of such thin materials, potentially limiting their applications in electronics and various critical systems.
Recent research has confirmed theoretical models indicating that elasticity varies with scale; specifically, the elastic properties of a material are not uniform but instead change depending on the dimensions of the material in question.
A collaborative study involving Assistant Professor Jian Zhou from Binghamton University and researchers from Argonne National Laboratory, Harvard University, Princeton University, and Penn State University has been published in the Proceedings of the National Academy of Sciences.
The team employed a semiconductor fabrication method to generate alumina structures with a thickness of 28 nanometers—over 1,000 times thinner than a human hair—on silicon wafers, creating thermally induced static ripples. They then utilized laser technology to assess the behavior of these structures. To mitigate any stress that could skew the results, the wafers were supported by cantilevers during testing.
The findings align with the theoretical models proposed by a research group led by the distinguished Harvard professor David R. Nelson, who contributed to the study.
“This marks the first instance in which we can accurately delineate the ripple effect on thin films,” stated Zhou, a member of the Thomas J. Watson College of Engineering and Applied Science’s Department of Mechanical Engineering.
Understanding the impact of these ripples is crucial, as it opens avenues for the fabrication of microelectronics, micromechanical devices, and miniature robots, paving the way for advancements in fields such as medicine and computing.
In a playful application of their findings, Zhou and his team manipulated the materials to fashion them into nanoscopic flower-like shapes.
“With enhanced knowledge of mechanical properties, we can develop superior structures such as micro-robots that allow for precise geometrical control,” Zhou explained. “For example, we can achieve real-time actuations where the material starts in one configuration and transforms into another—much like a Transformer!”
The research involved contributions from Richard Huang, a graduate student in Nelson’s group; Andrej Košmrlj, an associate professor at Princeton University; David A. Czaplewski, a scientist at Argonne National Laboratory; and Daniel López, a professor at Penn State University, all of whom are co-authors of the paper.
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