Nanoarchitected Schwarzites and Tubulanes with Ultrahigh Energy Absorption and Resilience

Nanoarchitected materials represent the frontier of low-density metamaterials that can achieve specific strengths and specific stiffnesses beyond the theoretical limit for solid materials. These nanoarchitected materials combine three synergistic effects – nanoscale size effects of individual elements, high performance constituent materials, and optimized shape factors – which are enabled through nanoscale additive manufacturing by two photon polymerization (2PP).¹ Of particular interest, post-2PP pyrolysis enables the printed 3D design to be converted to a mechanically high-performance carbon which has demonstrated rubber-like behaviour due to its nanoscale size and flaw tolerance.^2,3<br/> <br/>Leveraging the high mechanical performance of nanoarchitected carbon produced by 2PP and pyrolysis, we form Schwarzite and Tubulane structures which are designed from p-type Schwarz minimal surfaces and aligned cross-linked carbon nanotube architectures, respectively. These structures are optimized to minimize stress concentrations and therefore demonstrate specific strengths beyond the theoretical limit when subject to compression testing with failure strengths of several GPa at =50-70%. It is demonstrated that the strength and stiffness increase by nearly an order of magnitude as the wall-thickness of the architecture is reduced from several micron to several hundred nanometers, indicating the role of nanoarchitecture and size effects.<br/> <br/>Due to the flaw intolerance of the constituent pyrolyzed carbon, the nanoarchitectures exhibit ultra-high failure strain often exceeding ε=40% when the wall-thickness is on the order of several hundred nanometers. This equates to an enormous absorption of mechanical energy and the structures demonstrate nearly complete recoverability when subject to cyclic loading up to σ_y=95%. The modulus of resilience (U_R) represents the elastic energy absorption, and it is demonstrated that the nanoarchitected Schwarzite and Tubulane structures exhibit U_R more than an order of magnitude greater than Kevlar and other defence materials. <br/> <br/>We thus employ the nanoarchitectures towards absorption of dynamic energy including micro-ballistic impact testing at sub- and super-sonic velocities and atomic force microscope vibration damping from kHz to MHz frequency ranges. Both of these unique dynamic loading conditions demonstrate clear applications where the high dynamic performance of these nanoarchitected materials is vastly superior to conventional materials such as Kevlar and rubber. Nanoscale additive manufacturing of these optimized Schwarzite and Tubulane geometries thus demonstrates that the successes achieved in nanoarchitected materials can be further extended towards dynamic loading conditions with wide-reaching implications from vibration control and damping in device design, to resilient materials for aerospace, or lightweight ballistic impact materials for defence.<br/> <br/>1. Zhang, X., Wang, Y., Ding, B. & Li, X. Design, Fabrication, and Mechanics of 3D Micro-/Nanolattices. <i>Small</i>vol. 16 (2020).<br/>2. Zhang, X. <i>et al.</i> Theoretical strength and rubber-like behaviour in micro-sized pyrolytic carbon. <i>Nature Nanotechnology</i> <b>14</b>, 762–769 (2019).<br/>3. Serles, P. <i>et al.</i> Mechanically Robust Pyrolyzed Carbon Produced by Two-Photon Polymerization. <i>Carbon </i>(2022).