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(a) Illustration of Crookes radiometer; (b) the created light mill at the tips of tweezers; (c) SEM image of closely packed gold nanoparticles on the porous light mill blade; (d) illustration of asymmetric irradiation on the light mill, which rotates in the indicated direction; and (e) simulated rates of light absorption by the convex and concave surfaces at each blade vs the light mill rotation angle ; integrating the areas below each curve shows an approximately doubled rate of heating at the convex side compared to the concave side.
In experiments, the light mill rotates with the convex surfaces retreating from the source of lateral irradiation (enhanced online). [URL: http://dx.doi.org/10.1063/1.3431741.1]10.1063/1.3431741.1
Experimental data showing (a) light mill speed vs irradiation intensity at a constant pressure (400 mTorr) and (b) light mill speed vs pressure at a constant irradiation . Each error bar indicates standard deviation of five measurements.
Different modeling results: (a) accumulation of photon energy among close gold nanoparticles with interparticle space equals 1 nm; the field enhancement shows the ratio of enhanced energy density to the incident light; the arrow indicates incident electric field; (b) heat-induced gas momentum at 400 mTorr (highlighted by white arrows); the color map indicates gas temperature (high and low); (c) simulated collisions encountered by a surrounding gas molecule at 10 mTorr; and (d) at 1000 mTorr; the unit of axes is mm; the circular boundary defines a isothermal wall at which gas temperature remains constant (at ).
Simulated torque exerted by the circulating gas molecules at different gas pressures.
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