Stiff Shape Memory Polymers for High-Resolution Reconfigurable Nanophotonics

Abstract

Reconfigurable metamaterials require constituent nanostructures to demonstrate switching of shapes with external stimuli. Yet, a longstanding challenge is in overcoming stiction caused by van der Waals forces in the deformed configuration, which impedes shape recovery. Here, we introduce stiff shape memory polymers. This designer material has a storage modulus of ∼5.2 GPa at room temperature and ∼90 MPa in the rubbery state at 150 °C, 1 order of magnitude higher than those in previous reports. Nanopillars with diameters of ∼400 nm and an aspect ratio as high as ∼10 were printed by two-photon lithography. Experimentally, we observe shape recovery as collapsed and touching structures overcome stiction to stand back up. We develop a theoretical model to explain the recoverability of these sub-micrometer structures. Reconfigurable structural color prints with a resolution of 21150 dots per inch and holograms are demonstrated, indicating potential applications of the stiff shape memory polymers in high-resolution reconfigurable nanophotonics.

Two‐Photon Polymerization Lithography for Optics and Photonics: Fundamentals, Materials, Technologies, and Applications

“…[ 160 ] The printed structures can switch between the as‐printed state and deformed state, due to the switch of geometry between the as‐printed and deformed states ( Figure a). In a following work, [ 115 ] they developed a stiff SMP suitable for TPL, which is an acrylic acid (AAc) and HPPA copolymer SMP crosslinked by dipentaerythritol penta‐/hexa‐acrylate (DPEPA). By tuning the ratio of the crosslinker, storage modulus as high as 100 MPa in the rubbery state can be obtained, which is one order of magnitude higher than previous reports.…”

“…Reproduced with permission. [ 115 ] Copyright 2022, American Chemical Society. c) Vapor‐responsive photonic arrays.…”

Light and Shape‐Memory Polymers: Characterization, Preparation, Stimulation, and Application

“…At the same time, the ability of nanopillars with high storage modulus to overcome the friction in the pillars and the van der Waals force with the bottom surface was also explored when the secondary deformation restored the original shape with high aspect ratio structure, thereby realizing the ability of reconfigurable optical control. [199] In summary, the aforementioned five photocuring 3D printing technologies represent prevalent photo-forming methods employed in producing shape-memory materials, which offering suitability for different photo-forming 3D printing scenarios. TO provide a comprehensive overview, we summarized the light source requirements, printing resolution, printing area, and printing speed of these five photocure printing technologies in Table 3.…”

“…b) the mechanism of structural color change through SME with high-resolution reconfigurable structural color. Reproduced with permission [199]. Copyright 2022, American Chemical Society.…”

Fabrication of High‐Aspect Ratio Nanogratings for Phase‐Based X‐Ray Imaging

“…Those forces are responsible for sticking of surfaces together. [38,39] Consequently, the surface energy that enters Equation S3 (Supporting Information) is modified -L maxSE increases by a factor of three when surface energy is lowered by two orders of magnitude. Yet, we cannot brush off the fact that the surface interaction scenario comes with the surfaces already in contact.…”