Ultra-High Actuation Stress Polymer Actuators as Light-Driven Artificial Muscles

Abstract

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Transparent semi‐crystalline polymeric materials and their nanocomposites: A review

“…[142] Mechanical response of a 0.06 mol% C78-AZO-doped stretched UHMWPE film, C, utilizing a 365 nm LED source or, D, under increasing intensity of a 365 nm LED source. [83] E, Photo-thermal response observed upon UV exposure (0.9 A) of drawn 5 wt% BZT/UHMWPE film and, F, infrared images of 1 wt% BZT/UHMWPE film during a UV exposure cycle (10 seconds intervals) [84] [Color figure can be viewed at wileyonlinelibrary.com] fibrillary structures on the surface and in the bulk of the films after ultra-drawing will induce light scattering, resulting in a poor transparency in the visible light regime. [70,77] Thus, resultant opaque oriented polymer films have limited applicability in fields like built environment, impact resistant visors, screens, and automotive glazing where both high transparency and high mechanical properties are needed.…”

“…[150] F, Isomerization of spiropyran (SP) and merocyanine (MC) and photographs of drawn UHMWPE tapes containing SP before and after UV radiation, and, G, absorption spectra and corresponding pictures of drawn UHMWPE tapes containing SP irradiation with UV light at different radiation time [151] [Color figure can be viewed at wileyonlinelibrary.com] UHMWPE or HDPE films incorporating BZT can also lead to light-responsive polymer actuators with rapid response and exceptionally high actuation stress. [83][84][85] In case of a broad MWD (> 20), the drawn HDPE films revealed a high transparency (~90%) even without the incorporation of any additives at low draw ratios (~10) as shown in Figure 3B. [79] This is because here the low molecular-weight fraction could function as an additive with a relatively high refractive index that fills the voids.…”

“…It was recently shown that such transparent oriented UHMWPE or HDPE films incorporating BZT can also lead to light‐responsive polymer actuators with rapid response and exceptionally high actuation stress. [ 83‐85 ]…”

“…[ 142 ] Mechanical response of a 0.06 mol% C78‐AZO‐doped stretched UHMWPE film, C, utilizing a 365 nm LED source or, D, under increasing intensity of a 365 nm LED source. [ 83 ] E, Photo‐thermal response observed upon UV exposure (0.9 A) of drawn 5 wt% BZT/UHMWPE film and, F, infrared images of 1 wt% BZT/UHMWPE film during a UV exposure cycle (10 seconds intervals) [ 84 ] [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Recently, our research team also reported that the incorporation of photo‐responsive dyes or additives (like azobenzene C78‐AZO or a UV‐absorber BZT) to oriented transparent HDPE or UHMWPE films could induce photo‐thermal actuation as shown in Figure 9C‐F. [ 83‐85 ] Upon exposure to UV light, photo energy absorbed by the BZT is converted into heat. This in combination with the negative thermal expansion (NTE) coefficient of oriented PE results in contraction along the chain orientation direction and if constrained in an actuation stress.…”