RESUMO
Multimode motion of Marangoni propulsion ships on a water surface as per a near-infrared, two-wavelength selective response is achieved for the first time. The ships are rhombus- or propeller-shaped polyacrylamide or siloxane resin-based gels in which Nd2O3 and Yb2O3 nanoparticles are incorporated separately for photothermal conversion at 808 and 980 nm, respectively. The rhombus geometry is for straight locomotion, and the propeller geometry is for rotation. On/off remote control of the forward and backward locomotion of a rhombus-shaped ship and of the clockwise and counterclockwise rotations of a propeller-shaped ship via irradiation with 808 or 980 nm near-infrared light is demonstrated. The nanoparticles are incorporated into the desired locations of the gels, enabling selective local heating of the gels without focusing the light. The temperature gradient of the ships by local heating, based on a photothermal conversion, generates a Marangoni propulsion force to move the ship in the desired direction.
RESUMO
A mode-locked laser has been introduced in combination with synchrotron radiation to establish a versatile technique for highly time-resolved correlation measurements utilizing the short-pulse and high-pulse frequency characteristics of both photon sources. Successive pulse timing delay detected by nonlinear optical mixing between the two sources yields a cross-correlation profile capable of accurate measurement of the picosecond pulse profile of the synchrotron radiation without any synchronization control. Although the experiment was performed in the visible spectral domain, the present technique opens up a methodology for time-resolved spectroscopy in femtosecond and higher-energy domains by introducing a suitable nonlinear process that informs of the pulse coincidence between the two radiation sources.
