14 research outputs found
Compound droplet manipulations on fiber arrays
Recent works demonstrated that fiber arrays may constitue the basis of an
open digital microfluidics. Various processes, such as droplet motion,
fragmentation, trapping, release, mixing and encapsulation, may be achieved on
fiber arrays. However, handling a large number of tiny droplets resulting from
the mixing of several liquid components is still a challenge for developing
microreactors, smart sensors or microemulsifying drugs. Here, we show that the
manipulation of tiny droplets onto fiber networks allows for creating compound
droplets with a high complexity level. Moreover, this cost-effective and
flexible method may also be implemented with optical fibers in order to develop
fluorescence-based biosensor
Drop on a Bent Fibre
Inspired by the huge droplets attached on cypress tree leaf tips after rain,
we find that a bent fibre can hold significantly more water in the corner than
a horizontally placed fibre (typically up to three times or more). The maximum
volume of the liquid that can be trapped is remarkably affected by the bending
angle of the fibre and surface tension of the liquid. We experimentally find
the optimal included angle () that holds the most water.
Analytical and semi-empirical models are developed to explain these
counter-intuitive experimental observations and predict the optimal angle. The
data and models could be useful for designing microfluidic and fog harvesting
devices
Compound droplets on fibers
Droplets on fibers have been extensively studied in the recent years.
Although the equilibrium shapes of simple droplets on fibers are well
established, the situation becomes more complex for compound fluidic systems.
Through experimental and numerical investigations, we show herein that compound
droplets can be formed on fibers and that they adopt specific geometries. We
focus on the various contact lines formed at the meeting of the different
phases and we study their equilibrium state. It appears that, depending on the
surface tensions, the triple contact lines can remain separate or merge
together and form quadruple lines. The nature of the contact lines influences
the behavior of the compound droplets on fibers. Indeed, both experimental and
numerical results show that, during the detachment process, depending on
whether the contact lines are triple or quadruple, the characteristic length is
the inner droplet radius or the fiber radius
Magnetocapillary Swimmers
We present an experiment where three mesoscopic soft ferromagnetic beads are
placed onto a liquid surface and submitted to the influence of magnetic fields.
A vertical magnetic field creates a repulsion which counterbalances the
capillary attraction. We show that the competition with a second, oscillating
field, deforms the structure in a non reciprocal way. As a consequence, the
structure is able to swim. This experiment is fully described in a fluid
dynamics video attached to this submission.Comment: 5 pages, 6 figures and 2 videos for the gallery of fluid motion (The
same ones but at different qualities.