Laboratoire Matière et Systèmes Complexes

Microrheology in the beetles’ secretion

MSC : B. Abou

Collaboration : S. Gorb, Kiel University ; C. Gay, MSC

Pads of beetles are covered with long, deformable setae, each ending in a micrometric terminal plate coated with secretory fluid. However, less is known about the fluid itself because it is produced in an extremely small quantity.

A home-made microneedle, with a tip size of a few microns, was used to draw up the secretion droplets (1–10 µm in diameter) spread on a glass slide. Owing to capillary effects, the rise of the wetting secretion takes place spontaneously in the tube as the tip is maintained in contact with the support and the droplet. After an entire day (approx. 8 h) collecting the secretion, the final volume of fluid represented a drop which was about 100 µm in diameter and 30 µm in height !

Drawing up the beetles’ secretion

A dry powder of melamine beads was deposited on a clean glass slide. The collected secretion volume was then ejected on the dry beads by applying a positive pressure to the microneedle.

The thermal motion of the tracer beads immersed in the secretory fluid was recorded with a fast camera. We achieved this quantitative measurement with the collected volume (less than 1 nl), which is much smaller than the usual 1 ml sample volume required for this technique. The beetles’ secretion was found to be purely viscous (100 times the water viscosity), over the range of frequencies investigated. This indicates that the beetle locomotion might not need a specifically viscoelastic behaviour. We finally discuss the consequences of the secretion viscosity on the insect adhesion.

Microrheology in the jellyfish extracellular matrix

MSC : C. Gambini, B. Abou, A. Cornelissen

Evolution of local visco-elastic properties of the tissue in the jellyfish Aurelia Aurita is measured by introducing micrometric beads in the extracellular matrix, and measuring their thermal motion at different stages of jellyfish development.

The global aim of this study is to correlate in vivo observations of vascular morphogenesis with in vivo mechanical measurements of the growing surrounding tissue. For more details and beautiful pictures, click here.

Micro and macrorheology of jellyfish extracellular matrix , C. Gambini, B. Abou, A. Ponton and A. J. M. Cornelissen, Biohysical Journal, vol. 102, pp 1-9 (2012).

Intracellular microrheology probed by micron-sized wires

MSC : R. Colin, M. Yan, L. Chevry, J.-F. Berret, B. Abou

Intracellular microrheology probed by micron-sized wires, L. Chevry, R. Colin, B. Abou & J.-F. Berret, Biomaterials 34 6299 (2013).