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Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators.

Chen X, Goodnight D, Gao Z, Cavusoglu AH, Sabharwal N, DeLay M, Driks A, Sahin O - Nat Commun (2015)

Bottom Line: These engines start and run autonomously when placed at air-water interfaces.Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates.Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Columbia University, New York 10027, New York, USA.

ABSTRACT
Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

No MeSH data available.


Related in: MedlinePlus

The rotary engine.(a) Side view of a rotary engine. Wet paper provides the humidity gradient. Blue plastic blocks weighing 15 mg attached to HYDRAs increase the amount of mass shifting position relative to the axis of rotation. (b) Photos and (c) measurements showing the horizontal shifts in the positions of plastic blocks attached to HYDRAs. Markers indicate the average data values with error bars showing the s.d. calculated from measurements on five samples. (d) Rotation speed measured as a function of external relative humidity and at two different airflow speeds near the device. The rotary engine can drive a vehicle forward if its rotation is coupled to the wheels. (e) Snapshots showing the position of a miniature car driven by a rotary engine (see Supplementary Movie 5). Scale bars, 2 cm (a,e); 5 mm (b).
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f4: The rotary engine.(a) Side view of a rotary engine. Wet paper provides the humidity gradient. Blue plastic blocks weighing 15 mg attached to HYDRAs increase the amount of mass shifting position relative to the axis of rotation. (b) Photos and (c) measurements showing the horizontal shifts in the positions of plastic blocks attached to HYDRAs. Markers indicate the average data values with error bars showing the s.d. calculated from measurements on five samples. (d) Rotation speed measured as a function of external relative humidity and at two different airflow speeds near the device. The rotary engine can drive a vehicle forward if its rotation is coupled to the wheels. (e) Snapshots showing the position of a miniature car driven by a rotary engine (see Supplementary Movie 5). Scale bars, 2 cm (a,e); 5 mm (b).

Mentions: Although the oscillatory engine described so far meets the goal of a scalable device, many devices, particularly those that are used for locomotion, prefer rotary motion. Using the design concept in Fig. 1i, we developed a rotary engine (moisture mill) by assembling HYDRAs around two concentric rings, laser-cut from acrylic glass. Four or five such structures were connected in parallel via a central axis. The entire structure rotates freely around ball bearings (Methods and Supplementary Fig. 5 describe device assembly and characterization in more detail). As seen in Fig. 1j and Fig. 4a, the structure was inserted half way into an enclosure such that the HYDRAs face walls lined with paper (we left out the outermost wall to allow the HYDRAs to be viewed). To increase the torque, we attached small blocks of acrylic at the HYDRAs free ends. Photos (Fig. 4b) and measurements (Fig. 4c) show that the horizontal displacement of the acrylic block was as much as 5.5 mm when the relative humidity on the right side was reduced relative to the left side. As a result of this, the structure began to rotate when the paper was wetted (Supplementary Movie 2). Measurements in Fig. 4d show that the rotation speed depends on the relative humidity outside the chamber and the speed of airflow near the device. The increase in rotation speed with flow rate can be explained by the more efficient mixing with the surrounding air. We note that an airflow specifically directed at HYDRAs can induce torque to rotate the structure. In our case, this effect was negligible, since the data show that beyond a certain relative humidity, the rotations stop despite the presence of airflow.


Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators.

Chen X, Goodnight D, Gao Z, Cavusoglu AH, Sabharwal N, DeLay M, Driks A, Sahin O - Nat Commun (2015)

The rotary engine.(a) Side view of a rotary engine. Wet paper provides the humidity gradient. Blue plastic blocks weighing 15 mg attached to HYDRAs increase the amount of mass shifting position relative to the axis of rotation. (b) Photos and (c) measurements showing the horizontal shifts in the positions of plastic blocks attached to HYDRAs. Markers indicate the average data values with error bars showing the s.d. calculated from measurements on five samples. (d) Rotation speed measured as a function of external relative humidity and at two different airflow speeds near the device. The rotary engine can drive a vehicle forward if its rotation is coupled to the wheels. (e) Snapshots showing the position of a miniature car driven by a rotary engine (see Supplementary Movie 5). Scale bars, 2 cm (a,e); 5 mm (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4490384&req=5

f4: The rotary engine.(a) Side view of a rotary engine. Wet paper provides the humidity gradient. Blue plastic blocks weighing 15 mg attached to HYDRAs increase the amount of mass shifting position relative to the axis of rotation. (b) Photos and (c) measurements showing the horizontal shifts in the positions of plastic blocks attached to HYDRAs. Markers indicate the average data values with error bars showing the s.d. calculated from measurements on five samples. (d) Rotation speed measured as a function of external relative humidity and at two different airflow speeds near the device. The rotary engine can drive a vehicle forward if its rotation is coupled to the wheels. (e) Snapshots showing the position of a miniature car driven by a rotary engine (see Supplementary Movie 5). Scale bars, 2 cm (a,e); 5 mm (b).
Mentions: Although the oscillatory engine described so far meets the goal of a scalable device, many devices, particularly those that are used for locomotion, prefer rotary motion. Using the design concept in Fig. 1i, we developed a rotary engine (moisture mill) by assembling HYDRAs around two concentric rings, laser-cut from acrylic glass. Four or five such structures were connected in parallel via a central axis. The entire structure rotates freely around ball bearings (Methods and Supplementary Fig. 5 describe device assembly and characterization in more detail). As seen in Fig. 1j and Fig. 4a, the structure was inserted half way into an enclosure such that the HYDRAs face walls lined with paper (we left out the outermost wall to allow the HYDRAs to be viewed). To increase the torque, we attached small blocks of acrylic at the HYDRAs free ends. Photos (Fig. 4b) and measurements (Fig. 4c) show that the horizontal displacement of the acrylic block was as much as 5.5 mm when the relative humidity on the right side was reduced relative to the left side. As a result of this, the structure began to rotate when the paper was wetted (Supplementary Movie 2). Measurements in Fig. 4d show that the rotation speed depends on the relative humidity outside the chamber and the speed of airflow near the device. The increase in rotation speed with flow rate can be explained by the more efficient mixing with the surrounding air. We note that an airflow specifically directed at HYDRAs can induce torque to rotate the structure. In our case, this effect was negligible, since the data show that beyond a certain relative humidity, the rotations stop despite the presence of airflow.

Bottom Line: These engines start and run autonomously when placed at air-water interfaces.Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates.Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Columbia University, New York 10027, New York, USA.

ABSTRACT
Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

No MeSH data available.


Related in: MedlinePlus