Immersed cantilever apparatus for mechanics and microscopy

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 3D 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 6 mPa. 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.

Automated summary

The apparatus presented allows for stress or strain-controlled rheology in very soft solids, with simultaneous confocal imaging of the 3D microstructure. Stress is measured using eddy-based sensors and controlled by applying PID control loops and changing position using a micromanipulator, enabling stress measurement and control down to 6 mPa. The setup demonstrates the technical capability of independently applying shear and normal stress or strain with equal precision.