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Photogated humidity-driven motility.

Zhang L, Liang H, Jacob J, Naumov P - Nat Commun (2015)

Bottom Line: Here we demonstrate that mechanical bistability caused by rapid and anisotropic adsorption and desorption of water vapour by a flexible dynamic element that harnesses the chemical potential across very small humidity gradients for perpetual motion can be effectively modulated with light.A mechanically robust material capable of rapid exchange of water with the surroundings is prepared that undergoes swift locomotion in effect to periodic shape reconfiguration with turnover frequency of <150 min(-1).The element can lift objects ∼85 times heavier and can transport cargos ∼20 times heavier than itself.

View Article: PubMed Central - PubMed

Affiliation: New York University Abu Dhabi, PO Box 129188, Abu Dhabi, United Arab Emirates.

ABSTRACT
Hygroinduced motion is a fundamental process of energy conversion that is essential for applications that require contactless actuation in response to the day-night rhythm of atmospheric humidity. Here we demonstrate that mechanical bistability caused by rapid and anisotropic adsorption and desorption of water vapour by a flexible dynamic element that harnesses the chemical potential across very small humidity gradients for perpetual motion can be effectively modulated with light. A mechanically robust material capable of rapid exchange of water with the surroundings is prepared that undergoes swift locomotion in effect to periodic shape reconfiguration with turnover frequency of <150 min(-1). The element can lift objects ∼85 times heavier and can transport cargos ∼20 times heavier than itself. Having an azobenzene-containing conjugate as a photoactive dopant, this entirely humidity-driven self-actuation can be controlled remotely with ultraviolet light, thus setting a platform for next-generation smart biomimetic hybrids.

No MeSH data available.


Related in: MedlinePlus

Performance of bending PCAD@AG films.The y axis (in pixels) is the relative deflection of the tip of the film (for details on the kinematic analysis, see Supplementary Methods). The inset in each figure shows snapshots of the bending films. (a) Humidity-induced bending of films of PCAD@AG (16 mg) and pure AG (15 mg) of size 2 cm × 0.5 cm × 100 μm loaded with a cargo of 370 mg. (b) Humidity-induced bending of films of PCAD@AG and pure AG of size: 2 cm × 0.5 cm × 200 μm carrying a cargo of 370 mg (note the different scale on the y axis with a). (c) Performance of doped versus undoped film in humidity-induced bending (film size: 1 cm × 0.5 cm × 200 μm, cargo weight: 1,110 mg). (d) Effect of cargo weight on humidity-induced bending (film size: 2 cm × 0.5 cm × 200 μm, cargo weight: 370 mg and 1,110 mg). (e) Effect of ultraviolet power on photochemical bending (film size: 4 cm × 0.5 cm × 40 μm, ultraviolet power: 2–20 mW cm−2). (f) Effect of the length of the strip on the photochemical bending (ultraviolet light power: 20 mW cm−2). The numbers refer to the length of the strips. (g) Effect of film thickness on photochemical bending (ultraviolet power: 20 mW cm−2). (h) Effect of film thickness on the thermally induced bending of the films. The tip of a heated metal pin used as heat source is shown in the inset.
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f2: Performance of bending PCAD@AG films.The y axis (in pixels) is the relative deflection of the tip of the film (for details on the kinematic analysis, see Supplementary Methods). The inset in each figure shows snapshots of the bending films. (a) Humidity-induced bending of films of PCAD@AG (16 mg) and pure AG (15 mg) of size 2 cm × 0.5 cm × 100 μm loaded with a cargo of 370 mg. (b) Humidity-induced bending of films of PCAD@AG and pure AG of size: 2 cm × 0.5 cm × 200 μm carrying a cargo of 370 mg (note the different scale on the y axis with a). (c) Performance of doped versus undoped film in humidity-induced bending (film size: 1 cm × 0.5 cm × 200 μm, cargo weight: 1,110 mg). (d) Effect of cargo weight on humidity-induced bending (film size: 2 cm × 0.5 cm × 200 μm, cargo weight: 370 mg and 1,110 mg). (e) Effect of ultraviolet power on photochemical bending (film size: 4 cm × 0.5 cm × 40 μm, ultraviolet power: 2–20 mW cm−2). (f) Effect of the length of the strip on the photochemical bending (ultraviolet light power: 20 mW cm−2). The numbers refer to the length of the strips. (g) Effect of film thickness on photochemical bending (ultraviolet power: 20 mW cm−2). (h) Effect of film thickness on the thermally induced bending of the films. The tip of a heated metal pin used as heat source is shown in the inset.

Mentions: Hanging films of PCAD@AG affixed at their upper terminus that respond to non-uniform exposure to humid air by reversible bending can operate as cantilever cranes, which harvest energy of the chemical potential contained within the humidity gradient to convert it to mechanical work (Supplementary Movie 5). Lifting tests showed that hybrid films of any size performed better relative to films of pure AG under identical conditions (Fig. 2a–c; for details of the kinematic analysis see the Supplementary Methods). A 16 mg, 100-μm-thick film of PCAD@AG was capable of hoisting a cargo of 370 mg to a height of 2 cm with largest tip deflection in 1.2 s (Fig. 2a;Supplementary Fig. 6). This actuation is four orders of magnitude faster than that reported for a pNIPAm-microgel-based device (pNIPAm stands for poly(N-isopropylacrylamide)14. The work output and power density of this actuator (4.53 J kg–1 and 3.78 W kg–1, respectively) are also superior to those of pure AG films (1.13 J kg–1 and 0.94 W kg–1). Thicker films (200 μm) did not perform better (2.80 J kg–1 and 0.16 W kg–1; Fig. 2b and Supplementary Fig. 6), however, shortening of the film enhanced the bending force. A cargo of 1,110 mg was lifted to a height of 0.6 cm with work output 5.01 J kg–1 and power density 0.44 W kg–1 (Fig. 2c;Supplementary Fig. 6). For pure AG film of the same size, the work output was only 0.012 J kg–1 and the power density was 0.001 W kg–1. A maximum load of 740 mg on the PCAD@AG film (Fig. 2d) induced much lower stress (∼0.007 MPa) than the maximum elastic stress for moist (∼35 MPa) and dry (∼100 MPa) film (Fig. 1i). Thus, the film always operates in its elastic regime and efficiently overcomes the increased shear and stress. We estimated the theoretical limit of maximum load of a 200-μm-thick film within the elastic regime to a remarkable ∼3.5 kg (for details of the calculation, see the Supplementary Methods), although this theoretical limit is probably practically inaccessible at a reasonable rate.


Photogated humidity-driven motility.

Zhang L, Liang H, Jacob J, Naumov P - Nat Commun (2015)

Performance of bending PCAD@AG films.The y axis (in pixels) is the relative deflection of the tip of the film (for details on the kinematic analysis, see Supplementary Methods). The inset in each figure shows snapshots of the bending films. (a) Humidity-induced bending of films of PCAD@AG (16 mg) and pure AG (15 mg) of size 2 cm × 0.5 cm × 100 μm loaded with a cargo of 370 mg. (b) Humidity-induced bending of films of PCAD@AG and pure AG of size: 2 cm × 0.5 cm × 200 μm carrying a cargo of 370 mg (note the different scale on the y axis with a). (c) Performance of doped versus undoped film in humidity-induced bending (film size: 1 cm × 0.5 cm × 200 μm, cargo weight: 1,110 mg). (d) Effect of cargo weight on humidity-induced bending (film size: 2 cm × 0.5 cm × 200 μm, cargo weight: 370 mg and 1,110 mg). (e) Effect of ultraviolet power on photochemical bending (film size: 4 cm × 0.5 cm × 40 μm, ultraviolet power: 2–20 mW cm−2). (f) Effect of the length of the strip on the photochemical bending (ultraviolet light power: 20 mW cm−2). The numbers refer to the length of the strips. (g) Effect of film thickness on photochemical bending (ultraviolet power: 20 mW cm−2). (h) Effect of film thickness on the thermally induced bending of the films. The tip of a heated metal pin used as heat source is shown in the inset.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4490392&req=5

f2: Performance of bending PCAD@AG films.The y axis (in pixels) is the relative deflection of the tip of the film (for details on the kinematic analysis, see Supplementary Methods). The inset in each figure shows snapshots of the bending films. (a) Humidity-induced bending of films of PCAD@AG (16 mg) and pure AG (15 mg) of size 2 cm × 0.5 cm × 100 μm loaded with a cargo of 370 mg. (b) Humidity-induced bending of films of PCAD@AG and pure AG of size: 2 cm × 0.5 cm × 200 μm carrying a cargo of 370 mg (note the different scale on the y axis with a). (c) Performance of doped versus undoped film in humidity-induced bending (film size: 1 cm × 0.5 cm × 200 μm, cargo weight: 1,110 mg). (d) Effect of cargo weight on humidity-induced bending (film size: 2 cm × 0.5 cm × 200 μm, cargo weight: 370 mg and 1,110 mg). (e) Effect of ultraviolet power on photochemical bending (film size: 4 cm × 0.5 cm × 40 μm, ultraviolet power: 2–20 mW cm−2). (f) Effect of the length of the strip on the photochemical bending (ultraviolet light power: 20 mW cm−2). The numbers refer to the length of the strips. (g) Effect of film thickness on photochemical bending (ultraviolet power: 20 mW cm−2). (h) Effect of film thickness on the thermally induced bending of the films. The tip of a heated metal pin used as heat source is shown in the inset.
Mentions: Hanging films of PCAD@AG affixed at their upper terminus that respond to non-uniform exposure to humid air by reversible bending can operate as cantilever cranes, which harvest energy of the chemical potential contained within the humidity gradient to convert it to mechanical work (Supplementary Movie 5). Lifting tests showed that hybrid films of any size performed better relative to films of pure AG under identical conditions (Fig. 2a–c; for details of the kinematic analysis see the Supplementary Methods). A 16 mg, 100-μm-thick film of PCAD@AG was capable of hoisting a cargo of 370 mg to a height of 2 cm with largest tip deflection in 1.2 s (Fig. 2a;Supplementary Fig. 6). This actuation is four orders of magnitude faster than that reported for a pNIPAm-microgel-based device (pNIPAm stands for poly(N-isopropylacrylamide)14. The work output and power density of this actuator (4.53 J kg–1 and 3.78 W kg–1, respectively) are also superior to those of pure AG films (1.13 J kg–1 and 0.94 W kg–1). Thicker films (200 μm) did not perform better (2.80 J kg–1 and 0.16 W kg–1; Fig. 2b and Supplementary Fig. 6), however, shortening of the film enhanced the bending force. A cargo of 1,110 mg was lifted to a height of 0.6 cm with work output 5.01 J kg–1 and power density 0.44 W kg–1 (Fig. 2c;Supplementary Fig. 6). For pure AG film of the same size, the work output was only 0.012 J kg–1 and the power density was 0.001 W kg–1. A maximum load of 740 mg on the PCAD@AG film (Fig. 2d) induced much lower stress (∼0.007 MPa) than the maximum elastic stress for moist (∼35 MPa) and dry (∼100 MPa) film (Fig. 1i). Thus, the film always operates in its elastic regime and efficiently overcomes the increased shear and stress. We estimated the theoretical limit of maximum load of a 200-μm-thick film within the elastic regime to a remarkable ∼3.5 kg (for details of the calculation, see the Supplementary Methods), although this theoretical limit is probably practically inaccessible at a reasonable rate.

Bottom Line: Here we demonstrate that mechanical bistability caused by rapid and anisotropic adsorption and desorption of water vapour by a flexible dynamic element that harnesses the chemical potential across very small humidity gradients for perpetual motion can be effectively modulated with light.A mechanically robust material capable of rapid exchange of water with the surroundings is prepared that undergoes swift locomotion in effect to periodic shape reconfiguration with turnover frequency of <150 min(-1).The element can lift objects ∼85 times heavier and can transport cargos ∼20 times heavier than itself.

View Article: PubMed Central - PubMed

Affiliation: New York University Abu Dhabi, PO Box 129188, Abu Dhabi, United Arab Emirates.

ABSTRACT
Hygroinduced motion is a fundamental process of energy conversion that is essential for applications that require contactless actuation in response to the day-night rhythm of atmospheric humidity. Here we demonstrate that mechanical bistability caused by rapid and anisotropic adsorption and desorption of water vapour by a flexible dynamic element that harnesses the chemical potential across very small humidity gradients for perpetual motion can be effectively modulated with light. A mechanically robust material capable of rapid exchange of water with the surroundings is prepared that undergoes swift locomotion in effect to periodic shape reconfiguration with turnover frequency of <150 min(-1). The element can lift objects ∼85 times heavier and can transport cargos ∼20 times heavier than itself. Having an azobenzene-containing conjugate as a photoactive dopant, this entirely humidity-driven self-actuation can be controlled remotely with ultraviolet light, thus setting a platform for next-generation smart biomimetic hybrids.

No MeSH data available.


Related in: MedlinePlus