Application of the PIV technique to the study of air flow over Micro Electro-Mechanical Sensors (MEMS).

(A) Digital particle image velocity (PIV) measurements of the flow produced in front of a running spider. (B) Flow field around a running spider. The sequence highlights the pockets of high air flow velocity created by leg strokes superposed on the air movements created by the body trunk movement. From Casas et al. 2008 Plos ONE.

Publication/ Talks :

Casas J & Steinmann T (2014) Flow disturbances during attack explain variation in predator foraging modes. (In revision for Proceedings of the Royal Society B)

G.J.M Krijnen, H. Droogendijk, T. Steinmann, A.M.K. Dagamseh, R.K. Jaganatharaja and J. Casas (2014) Hair-based ow-sensing inspired by the cricket cercal system, Handbook of Biomimetics and Bioinspiration

T. Steinmann & J. Casas (2013). Laser-based methods for analyzing fluid flow sensing by organisms. In Flow sensing in air and water, H. Bleckmann & J. Mogdans. Springer Verlag.

F. Dupuy, T. Steinmann, D. Pierre, JP. Christidès, G. Cummins, C. Lazzari, J. Miller, and J. Casas (2012) Responses of cricket cercal interneurons to realistic naturalistic stimuli in the field, Journal of Experimental Biology, in press

E L Morley, T Steinmann, J Casas, and D Robert (2012) Directional cues in Drosophila melanogaster audition: structure of acoustic flow and inter-antennal velocity differences, Journal of Experimental Biology, in press

T Steinmann and J Casas (2011) Impact of the aerodynamical signature of attacking spiders on the sensory performance of prey, Flow sensing in air and water, 18-21 July 2011, Bonn, Germany

T Steinmann and J Casas (2011) Impact of the aerodynamical signature of attacking spiders on the sensory performance of prey, International Workshop on bio inspired robots, 6-8 April 2011, Nantes, France

B Bathellier, T Steinmann, F G. Barth and J Casas (2011) Air motion sensing hairs of arthropods detect high frequencies at near-maximal mechanical efficiency. J. R. Soc. Interface (online) doi: 10.1098/rsif.2011.0690

Casas J, Steinmann T, and Krijnen G (2010) Why do insects have such a high density of flow-sensing sensors hairs? Insights from the hydromechanics of biomimetic MEMS. J. R. Soc. Interface 7, 1487-1495. doi: 10.1098/rsif.2010.0093

Steinmann T., Casas J. (2008) Viscous coupling between mechanosensing hairs, Invertebrate sound and vibration Meeting, 2008 Tours, France

Casas J, Steinmann T, Dangles O (2008). The Aerodynamic Signature of Running Spiders. Plos ONE. 3(5): e2116. doi:10.1371/journal.pone.0002116.

Dangles O, Steinmann T, Pierre D, Vannier F, Casas J (2008). Relative contributions of organ shape and receptor arrangement to the design of cricket's cercal system. Journal of Comparative Physiology A. In Press.

Steinmann T, Casas J, Krijnen G, Dangles O (2006). Air-flow sensitive hairs: boundary layers in oscillatory flows around arthropod appendages. Journal of Experimental Biology 209: 4398-4408.

Dangles O, Ory N, Steinmann T, Christides JP, Casas J (2006). Spider's attack vs. cricket's escape: velocity

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2003- present. Engineer (Ingénieur d'études) - IRBI (France).
2002-2003. Laboratoire de Physique Appliquée aux semi- conducteurs, Strasbourg.

Keywords:
Sensory Ecology; Fluid and Solid mechanics; Particle Image Velocimetry .

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Wolf spiders are a typical example of running predator. They hunt in leaf litter either using an ambush strategy or by moving at high speed, taking over unwary preys. Air flow upstream of hunting spiders is a source of information for escaping prey, such as crickets and cockroaches. Using digital particle image velocimetry, we showed that running spiders are highly conspicuous aerodynamically, due to substantial air displacement detectable up to several centimetres in front of them.

I am also studying the early warning system in crickets which detect flying or running predators using air-flow-sensitive hairs on cerci, two long appendages at their rear.

Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) techniques were applied here to characterise both types of oscillatory flows around cricket cerci as a function of flow velocity and frequency.

The strong spatial heterogeneity of flow velocity around filiform-shaped appendages is a rich source of information for various flow-sensing animals. Our results suggest that crickets could detect the direction of incoming danger by having air-flow-sensitive hairs positioned around their entire cerci.

The study of vibratory communication in insects revealed the high influence of the geometry and composition of the substrate through which wavy signals are propagating. To be correctly understood by the receiver, the emitter has to consider these effects, which are consequences of several phenomena like filtering frequency or dispersion of signals. Quantification of such processes necessitates non-contact measurements by mean of laser vibrometry, to preserve the signal integrity, and the use of powerful analysis methods like wavelets and time frequency analysis.

We have visualized the flow around single MEMS sensors and the canopy effects with many sensors Single and tandem MEMS hairs of varying interhair distances were subjected to oscillatory flows of varying frequency.

Decreasing hair-to-hair distance markedly reduced flow velocity amplitude and increased the phase shift between the far-field flow and the flow between hairs.

These effects were stronger for lower flow frequencies. We predict strong hydrodynamic coupling within whole natural hair canopies exposed to natural stimuli, depending on arthropod and hair sizes, and hair density.

Thus, rather than asking why arthropods have so many hairs, it may be useful to address why hairs are packed together at such high densities, particularly given the exquisite sensitivity of a single hair.