Bouncing gel balls: impact of soft gels onto rigid surface

TL;DR

This study investigates how very soft gel balls bounce on rigid surfaces, revealing impact velocity effects on deformation and contact time, supported by experimental scaling relations and physical modeling.

Contribution

It introduces new scaling laws for gel ball deformation and contact time during impact, supported by experimental data and physical interpretation.

Findings

Gel balls behave nearly elastically at small impacts.

Deformation transitions from spherical to pancake shape at higher velocities.

Scaling relations accurately describe impact dynamics.

Abstract

After thrown onto a solid substrate, very soft spherical gels bounce repeatedly. Separate rheological measurements suggest that these balls can be treated as nearly elastic. The Hertz contact deformation expected in the static (elastic) limit was observed only at very small impact velocities. For larger velocities, the gel ball deformed into flattened forms like a pancake. We measured the size of the gel balls at the maximal deformation and the contact time as a function of velocities for the samples different in the original spherical radius and the Young modulus. The experimental results revealed a number of scaling relations. To interpret these relations, we developed scaling arguments to propose a physical picture.