Immersed Cantilever Apparatus for Mechanics and Microscopy

TL;DR

This paper introduces a novel immersed cantilever apparatus capable of precise stress and strain control in soft solids, combined with confocal microscopy for microstructural analysis, enabling detailed rheological studies.

Contribution

The work presents a new apparatus integrating stress measurement, control, and confocal imaging for soft solids, allowing simultaneous mechanical and microstructural investigation.

Findings

Achieved stress measurement down to 3mPa.

Demonstrated independent shear and normal stress control.

Provided microstructural insights during shear experiments.

Abstract

We present here a novel cantilever based apparatus to perform translational stress or strain controlled rheology in very soft solids, and obtain simultaneous confocal imaging of the 3 dimensional microstructure. The stress is measured using eddy based sensors. Both the stress and strain are controlled by applying PID control loops on measured quantities and changing position using a micromanipulator. To get rid of surface tension forces, the sample and cantilever are immersed. This enables stress measurement and control down to 3mPa. With this apparatus, we can independently apply shear and normal stress, or strain, with same precision. We demonstrate the technical capability of the setup with steady shear strain or stress experiments on a soft protein gel system. The simultaneous confocal imaging offers insight into the macroscopic breaking observed in an increasing shear strain experiment.