3 research outputs found
Color and Texture Morphing with Colloids on Multilayered Surfaces
Dynamic
morphing of marine species to match with environment changes in color
and texture is an advanced means for surviving, self-defense, and
reproduction. Here we use colloids that are placed inside a multilayered
structure to demonstrate color and texture morphing. The multilayer
is composed of a thermal insulating base layer, a light absorbing
mid layer, and a liquid top layer. When external light of moderate
intensity (∼0.2 W cm<sup>–2</sup>) strikes the structure,
colloids inside the liquid layer will be assembled to locations with
an optimal absorption. When this system is exposed to continuous laser
pulses, more than 18 000 times of reversible responses are
recorded, where the system requests 20 ms to start the response and
another 160 ms to complete. The flexibility of our concept further
allows the system to be built on a variety of light-absorbing substrates,
including dyed paper, gold thin film, and amorphous silicon, with
the top layer even a solid
Extraordinary Shifts of the Leidenfrost Temperature from Multiscale Micro/Nanostructured Surfaces
In
the present work, the effects of surface chemistry and micro/nanostructuring
on the Leidenfrost temperature are experimentally investigated. The
functional surfaces were fabricated on a 304 stainless steel surface
via femtosecond laser surface processing (FLSP). The droplet lifetime
experimental method was employed to determine the Leidenfrost temperature
for both machine-polished and textured surfaces. A precision dropper
was used to control the droplet size to 4.2 μL and surface temperatures
were measured by means of an embedded thermocouple. Extraordinary
shifts in the Leidenfrost temperatures, as high as 175 °C relative
to the polished surface, were observed with the laser-processed surfaces.
These extraordinary shifts were attributed to nanoporosity, reduction
in contact angle, intermittent liquid/solid contacts, and capillary
wicking actions resulting from the presence of self-assembled nanoparticles
formed on the surfaces. In addition to the shift in the Leidenfrost
temperature, significant enhancement of the heat transfer in the film
boiling regime was also observed for the laser-processed surfaces;
water droplet evaporation times were reduced by up to 33% for a surface
temperature of 500 °C
Extraordinary Shifts of the Leidenfrost Temperature from Multiscale Micro/Nanostructured Surfaces
In
the present work, the effects of surface chemistry and micro/nanostructuring
on the Leidenfrost temperature are experimentally investigated. The
functional surfaces were fabricated on a 304 stainless steel surface
via femtosecond laser surface processing (FLSP). The droplet lifetime
experimental method was employed to determine the Leidenfrost temperature
for both machine-polished and textured surfaces. A precision dropper
was used to control the droplet size to 4.2 μL and surface temperatures
were measured by means of an embedded thermocouple. Extraordinary
shifts in the Leidenfrost temperatures, as high as 175 °C relative
to the polished surface, were observed with the laser-processed surfaces.
These extraordinary shifts were attributed to nanoporosity, reduction
in contact angle, intermittent liquid/solid contacts, and capillary
wicking actions resulting from the presence of self-assembled nanoparticles
formed on the surfaces. In addition to the shift in the Leidenfrost
temperature, significant enhancement of the heat transfer in the film
boiling regime was also observed for the laser-processed surfaces;
water droplet evaporation times were reduced by up to 33% for a surface
temperature of 500 °C