posted on 2024-02-23, 15:05authored byAnne-Déborah
C. Nguindjel, Stan C. M. Franssen, Peter A. Korevaar
Droplets are attractive
building blocks for dynamic matter
that
organizes into adaptive structures. Communication among collectively
operating droplets opens untapped potential in settings that vary
from sensing, optics, protocells, computing, or adaptive matter. Inspired
by the transmission of signals among decentralized units in slime
mold Physarum polycephalum, we introduce
a combination of surfactants, self-assembly, and photochemistry to
establish chemical signal transfer among droplets. To connect droplets
that float at an air–water interface, surfactant triethylene
glycol monododecylether (C12E3) is used for
its ability to self-assemble into wires called myelins. We show how
the trajectory of these myelins can be directed toward selected photoactive
droplets upon UV exposure. To this end, we developed a strategy for
photocontrolled Marangoni flow, which comprises (1) the liquid crystalline
coating formed at the surface of an oleic acid/sodium oleate (OA/NaO)
droplet when in contact with water, (2) a photoacid generator that
protonates sodium oleate upon UV exposure and therefore disintegrates
the coating, and (3) the surface tension gradient that is generated
upon depletion of the surfactant from the air–water interface
by the uncoated droplet. Therefore, localized UV exposure of selected
OA/NaO droplets results in attraction of the myelins such that they
establish reconfigurable connections that self-organize among the
C12E3 and OA/NaO droplets. As an example of
communication, we demonstrate how the myelins transfer fluorescent
dyes, which are selectively delivered in the droplet interior upon
photochemical regulation of the liquid crystalline coating.