2026-04-27 11:04:57
SPEAKER: Mehmet Kepenekci, PhD Candidate, Department of Mechanical Engineering at The University of Texas at Austin, USA
Bioinspired Nanostructured Surfaces: Mechanics, Optics, and Multifunctionality
Date: May 21, 2026 (Thursday)
Time: 13:30
Place: EA-101


ABSTRACT

Biological nanostructures found in nature, such as moth eyes and lotus leaves, achieve remarkable optical and self-cleaning properties through their nanostructured surfaces. Translating these bioinspired designs into engineered materials offers a transformative opportunity to create surfaces that simultaneously exhibit antireflection, self-cleaning, dust mitigation, and mechanical durability—properties critical for applications in photonics, aerospace, and display technologies. This seminar presents research on the design, fabrication, and characterization of subwavelength nanopillar arrays on silicon and sapphire substrates, inspired by the moth-eye structure. Fabricated using interference lithography and inductively coupled plasma reactive ion etching, these nanostructures are systematically studied to understand how pillar geometry governs mechanical behavior and optical transmission, while also providing wetting control and dust mitigation functionality. A central focus of the seminar is the mechanical characterization of nanopillar arrays with different pillar aspect ratios. Mechanical modeling together with nanoindentation measurements reveal distinct deformation mechanisms as a function of aspect ratio on silicon nanopillar arrays. For sapphire nanopillar arrays, the influence of aspect ratio on optical and mechanical performance is investigated. High aspect ratio nanopillars broaden the antireflection bandwidth but reduce mechanical performance, whereas low aspect ratio nanopillars achieve comparable optical performance in the visible range while exhibiting hardness comparable to glass. These findings demonstrate that mechanical robustness and optical functionality can be simultaneously engineered in nanostructured surfaces. The seminar will conclude with future research directions, including multiphysics co-optimization of mechanical and optical performance, fabrication of monolithic nanostructured surfaces on hard ceramics, post-exposure mechanical reliability under extreme thermal cycling, and emerging applications in extreme environments.

ABOUT THE SPEAKER

Mehmet Kepenekci is a Ph.D. candidate in Mechanical Engineering at The University of Texas at Austin, working in the Nanostructures & Nanomanufacturing Laboratory under the supervision of Prof. Chih-Hao Chang. He received his B.S. (2018) and M.S. (2021) degrees in Mechanical Engineering from Middle East Technical University in Ankara, Türkiye. His research focuses on the fabrication and mechanical characterization of bioinspired nanostructures, with an emphasis on mechanically robust multifunctional surfaces. His current work investigates how nanopillar geometry influences deformation mechanisms, hardness, scratch resistance, and optical performance of subwavelength nanopillar arrays on silicon and sapphire substrates.

CONTACT

Ela Baycan, Mechanical Engineering Department, Bilkent University
E-mail: ela@bilkent.edu.tr