432 research outputs found
Initial spreading of low-viscosity drops on partially wetting surfaces
Liquid drops start spreading directly after brought into contact with a
partial wetting substrate. Although this phenomenon involves a three-phase
contact line, the spreading motion is very fast. We study the initial spreading
dynamics of low-viscosity drops, using two complementary methods: Molecular
Dynamics simulations and high-speed imaging. We access previously unexplored
length- and time-scales, and provide a detailed picture on how the initial
contact between the liquid drop and the solid is established. Both methods
unambiguously point towards a spreading regime that is independent of
wettability, with the contact radius growing as the square root of time
Interaction of two walkers: Wave-mediated energy and force
A bouncing droplet, self-propelled by its interaction with the waves it
generates, forms a classical wave-particle association called a "walker."
Previous works have demonstrated that the dynamics of a single walker is driven
by its global surface wave field that retains information on its past
trajectory. Here, we investigate the energy stored in this wave field for two
coupled walkers and how it conveys an interaction between them. For this
purpose, we characterize experimentally the "promenade modes" where two walkers
are bound, and propagate together. Their possible binding distances take
discrete values, and the velocity of the pair depends on their mutual binding.
The mean parallel motion can be either rectilinear or oscillating. The
experimental results are recovered analytically with a simple theoretical
framework. A relation between the kinetic energy of the droplets and the total
energy of the standing waves is established.Comment: 11 pages, 8 figure
Elastodynamics of a soft strip subject to a large deformation
To produce sounds, we adjust the tension of our vocal cords to shape their
properties and control the pitch. This efficient mechanism offers inspiration
for designing reconfigurable materials and adaptable soft robots. However,
understanding how flexible structures respond to a significant static strain is
not straightforward. This complexity also limits the precision of medical
imaging when applied to tensioned organs like muscles, tendons, ligaments and
blood vessels among others. In this article, we experimentally and
theoretically explore the dynamics of a soft strip subject to a substantial
static extension, up to 180\%. Our observations reveal a few intriguing
effects, such as the resilience of certain vibrational modes to a static
deformation. These observations are supported by a model based on the
incremental displacement theory. This has promising practical implications for
characterizing soft materials but also for scenarios where external actions can
be used to tune properties
- …