Powering miniature robots using actuating materials that mimic skeletal muscle is attractive because conventional mechanical drive systems cannot be readily downsized. However, muscle is not the only mechanically active system in nature, and the thousandfold contraction of eukaryotic DNA into the cell nucleus suggests an alternative mechanism for high-stroke artificial muscles. Our analysis reveals that the compaction of DNA generates a mass-normalized mechanical work output exceeding that of skeletal muscle, and this result inspired the development of composite double-helix fibers that reversibly convert twist to DNA-like plectonemic or solenoidal supercoils by simple swelling and deswelling. Our modeling-optimized twisted fibers give contraction strokes as high as 90% with a maximum gravimetric work 36 times higher than skeletal muscle. We found that our supercoiling coiled fibers simultaneously provide high stroke and high work capacity, which is rare in other artificial muscles.

We report the discovery of a broad, 1.°5 long filamentary [O iii] emission nebulosity some 1.°2 southeast of the M31 nucleus. This nebulosity is not detected in Hα and has no obvious emission counterparts in X-ray, UV, optical, infrared, and radio surveys. To our knowledge, this emission feature has not been previously reported in the literature. We briefly discuss its possible origin.

Photocontrolled directional transport in both 2D and 3D of water-in-oil droplets was achieved by merocyanine/spiropyran photoisomerization in the droplet.

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