posted on 2019-04-01, 19:04authored byYasuyuki Yamamoto, Shiho Tokonami, Takuya Iida
Light-induced
heating on a solid–liquid interface can generate
a vapor submillimeter bubble and fluid flow, which enables us to densely
and rapidly assemble dispersoids into a desired position (photothermal
assembly). Here, we revealed that the surface modulation of the light-induced
bubble by a surfactant dominates the assembly dynamics of nanoparticles
and microparticles as dispersoids, which results in highly efficient
photothermal assembly under the surfactant-controlled fluid flow.
This mechanism can facilitate the concentration measurement of small
objects (microparticles, bacteria, viruses, etc.). Particularly, we
found that the surfactant-controlled fluid flow and bubble enable
high-density assembly of dispersoids and remarkable enhancement of
assembly efficiency, achieving 10–20 times in comparison with
the case of no surfactant. This result can extend the limit of measurable
concentration by one order. Furthermore, this study revealed the influence
of concentration, size, and constituent material of the dispersoids
on the assembly efficiency for the improvement of measurement precision.
These findings are crucial for laser-induced assembly for the rapid
concentration measurement of various microbes without a cultivation
process as bioanalysis, for the high-sensitivity detection of harmful
particles, and for the colloidal lithography.