Fabrication and Mechanical Behavior of Hierarchical Architected Metamaterials

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

This grant supports advanced manufacturing through a study of multiphoton lithography of hierarchical architected metamaterials, providing an avenue for both scientific and technological progress which contributes to national prosperity. Multiphoton lithography is an additive manufacturing technique that enables the printing of complex structures in three dimensions with nanoscale features and resolution. While the principles of laser-material interactions for photopolymerization are well understood, their effects on the mechanical properties of the printed material have not been studied thoroughly. This poses obstacles in the modeling of such structures and their utility in functional material systems. This award supports the fundamental research required to unravel the effects of multiphoton lithography on the mechanical behavior and efficient design of 3D structures such as bioscaffolds. This project enables accurate modeling of the mechanical response of these structures in relation to the processing parameters. Furthermore, it paves the way for the scalability of multiphoton lithography and its use in diverse fields, including healthcare, bioengineering, and aerospace. The results from this research constitute a critical asset in the U.S. economy and society. The research involves several disciplines, including manufacturing, materials science, mechanics, and biochemistry. This multi-disciplinary approach serves as a catalyst for positive impact in engineering education for women and underrepresented minority students. Multiphoton lithography (MPL) can surpass several barriers related to the fabrication of extremely complex, mechanically robust three-dimensional (3D) structures in nano- and microscale. However, a major obstacle hindering advance of the scalability and wide applicability of this technique is the limited understanding on the constitutive mechanical behavior of the fabricated materials as a function of the processing parameters. This research is designed to comprehend the effect of MPL fabrication parameters on the mechanical behavior of hierarchical architected metamaterials. Through ex situ TEM analysis of defect formation and in situ SEM mechanical testing experiments, the mechanical performance of these materials is evaluated with respect to properties such as ductility, strength, critical fracture toughness and therefore enable accurate constitutive modeling of these materials. These models involve finite element analysis (FEA) and molecular dynamics (MD) simulations towards predicting the mechanical performance of complex 3D structures, validated through the design and manufacture of bioscaffolds that can possess multifunctional behavior. The results of the characterization experiments are used to reveal the enhanced mechanical performance and scalability of the architected material designs, thereby elucidating the full potential of MPL. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.