Vanderbilt Institute of Nanoscale Science and Engineering Colloquium
Dr. Daniel Lopez
Liang Professor of Electrical Engineering
Director, Nanofabrication Lab, Materials Research Institute
Founder, Mid-Atlantic Semiconductor Hub (MASH)
Penn State University
Ultrathin mechanical systems: an emerging field with new physics and unique applications.
10.22.25 | 4:10PM |
Micro and Nano Electro Mechanical Systems (MEMS, NEMS), made with structural materials just a few nanometers thick, are an exciting and rapidly growing area of research. They leverage the unique properties of materials at such a small scale to develop mechanical devices with new physics and unusual dynamic responses. Their mechanical behavior is dominated by thermal fluctuations and disorder, making traditional mechanical models inadequate to describe them.
As materials become thinner to the nanoscale, ripples spontaneously form due to thermal fluctuations, but their exact effect on mechanical properties remains controversial. Despite decades of theoretical research on the mechanics of ultra-thin structures, disagreement still exists about how these ripples impact behavior, with conflicting predictions on whether elasticity depends on scale or not. Experimental progress has been limited by the lack of a platform capable of fully isolating and analyzing the effects of ripples. This knowledge gap restricts the fundamental understanding of thin materials and their practical uses.
In this seminar, I will demonstrate that thermal-like ripples shape thin films into a new class of metamaterials with size-dependent, adjustable elasticity. Utilizing a scalable semiconductor manufacturing process, we engineered nanometer-thick cantilevers with precisely controlled frozen random ripples resembling snapshots of thermally fluctuating membranes [1]. Resonant frequency measurements of the rippled cantilevers reveal that random ripples effectively renormalize and enhance the average bending rigidity in a scale-dependent manner, consistent with recent theoretical estimations. The predictive power of the theoretical model, combined with the scalability of the fabrication process, were further exploited to create kirigami architectures with exceptional bending rigidity and mechanical metamaterials with delayed buckling instability.
[1] Zhou, Jian, et al. “Rippled metamaterials with scale-dependent tailorable elasticity.” PNAS 122.12 (2025): e2425200122.
Bio: Daniel Lopez is the Liang Professor of Electrical Engineering at Penn State University, the Director of the Nanofabrication Lab at the Materials Research Institute, and the founder of the Mid-Atlantic Semiconductor Hub (MASH). He earned his Ph.D. in Physics from the Centro Atómico Bariloche in Argentina in 1996. Afterward, he joined the IBM T. J. Watson Research Center as a Postdoctoral Fellow, and in 1998, he became a Research Staff member at Bell Laboratories (Murray Hill, NJ). In 2008, he moved to Argonne National Laboratory to lead the Nanofabrication and Devices group within the Center for Nanoscale Materials. In 2020, after a sabbatical year at NIST focused on quantum packaging for atomic sensors, Dr. Lopez joined Penn State University as a named Professor of Electrical Engineering and Director of the Nanofabrication Laboratory. During 2022, he established the Mid-Atlantic Semiconductor Hub (MASH), a consortium of multiple universities, semiconductor companies, national labs, and workforce development organizations that consolidates resources and expertise to support the U.S. semiconductor industry. He also maintains an affiliation with the Microsystems and Nanotechnology Division within the Physical Measurement Laboratory at NIST in Gaithersburg, Maryland. His research spans diverse fields, including novel materials, micromechanics, optical microsystems, and packaging.