Journal: Advanced Materials (Deerfield Beach, Fla.)

Article Title: Self‐Oscillating Helix Showing Amplified Winding and Unwinding Motions

doi: 10.1002/adma.202521736

Figure Lengend Snippet: Thermally, chemically, and NIR‐responsive shrinking behaviors of poly(NIPAAm) helix. a) Scheme of the motion of a Vorticella ’s stalk in response to external threats (physical or chemical stimuli) from predators. b) Optical images showing the thermal‐induced shrinking of poly(NIPAAm) helix during gradual heating from 25°C to 50°C. H , p , α , and L denote axial length, pitch length, pitch angle, and total length, respectively. c) Comparison of normalized axial ( H/H 0 ) and total ( L/L 0 ) length changes of the poly(NIPAAm) helix during heating. d) Plots showing the variations in the number of turns ( n , left y ‐axis) and pitch angle ( α , right y ‐axis) of the poly(NIPAAm) helix during heating. n was calculated as H/p . e) Finite Element Method (FEM) simulation results showing the strain distribution within the poly(NIPAAm) helix during thermal shrinkage. The color map represents the maximum principal logarithmic strain (LE, Max. Principal). f) Comparison of experimental (Exp.) and finite element method (FEM) simulation results of the poly(NIPAAm) helix before heating (25°C) and after heating (50°C). The bar graphs show changes in H 50°C / H 25°C , n 50°C / n 25°C , and α 25°C – α 50°C , representing the axial length ratio, number‐of‐turns ratio, and pitch‐angle change, respectively. g) Chemically induced shrinking of the poly(NIPAAm) helix (left) and the corresponding change in H (right). A sponge containing 60 wt.% nitric acid was introduced into water at 25°C to generate localized acidic stimuli. h) NIR‐induced shrinking of the poly(NIPAAm) helix (left) and the corresponding change in H (right) under localized irradiation in a 0.01 wt.% graphene oxide aqueous solution at 25°C. i) Schematic illustration of a poly(NIPAAm) helix with a gradual variation in 2 r along its axis, where 2 r L (1.49 mm) is larger than 2 r R (1.16 mm), wrapped around a taut string. j) Time‐lapse images showing stepwise translation during periodic heating and cooling in water using a Peltier plate at 70°C for 1500 s and 5°C for 1500 s. k) Tracked positions of the left foot, right foot, and center along the string and the corresponding change in helix length calculated as the distance between the two feet.

Article Snippet: We performed the FEM simulation using commercial software ABAQUS/Standard (see for details).

Techniques: Comparison, Irradiation