# Granular rheology: measuring boundary forces with laser-cut leaf springs

## TL;DR

This paper introduces a novel method using laser-cut leaf springs to measure boundary forces in 2D granular rheology experiments, enabling detailed stress analysis and accurate determination of shear properties.

## Contribution

The authors develop a new boundary force measurement technique using laser-cut leaf springs, allowing for spatially and temporally resolved stress data in granular rheology experiments.

## Key findings

- Enabled precise boundary stress measurements in 2D granular systems.
- Allowed calculation of shear stress and frictional properties.
- Demonstrated the technique's effectiveness in rheological characterization.

## Abstract

In granular physics experiments, it is a persistent challenge to obtain the boundary stress measurements necessary to provide full a rheological characterization of the dynamics. Here, we describe a new technique by which the outer boundary of a 2D Couette cell both confines the granular material and provides spatially- and temporally- resolved stress measurements. This key advance is enabled by desktop laser-cutting technology, which allows us to design and cut linearly-deformable walls with a specified spring constant. By tracking the position of each segment of the wall, we measure both the normal and tangential stress throughout the experiment. This permits us to calculate the amount of shear stress provided by basal friction, and thereby determine accurate values of $\mu(I)$.