(694b) Elastobuoyant Heavy Spheres in a Soft Gel : Understanding Large Deformations in Soft Elastic Polymeric Gels

Elastobuoyant
Heavy Spheres in a Soft Gel : Understanding large deformations in
soft elastic
polymeric gels

Aditi
Chakrabarti* and Manoj Chaudhury

Department
of Chemical and Biomolecular Engineering, Lehigh University,
Bethlehem, PA 18015, USA

Serge
Mora

Laboratoire
de Mécanique et de Génie Civil. UMR 5508,

Universit´e
Montpellier and CNRS. 163 Rue Auguste Broussonnet. F-34090
Montpellier, France.

Yves
Pomeau

University
of Arizona, Department of Mathematics, Tucson, USA.

Soft
solids undergoing large deformations exhibit various fascinating and
puzzling mechanical behaviors, yet systematic studies and methods to
understand the mechanics of such huge strains are lacking. Here we
investigate this complex problem systematically with a simple
experiment: by introducing a heavy bead of radius â??aâ??
in an incompressible ultra-soft elastic medium, by varying the sphere
radius and medium elasticity. For the softest gels, the sphere
becomes elastobuoyant at a particular depth (δ)
inside the gel, where its weight balances the mediumâ??s elastic
strain energy. The scaling law that we find for the penetration depth
of the bead at this regime is very different from what one would
expect in the small deformation limit. We develop an original
asymptotic analytic model to explain such large deformation behavior
that is consistent with our experimental observations. Ultimately, we
show that such huge deformations in ultra-soft materials can be
utilized in many different ways, for example, driving
three-dimensional self-assembly of particles inside such a substrate!