Sensor networks are made up of small battery-powered sensing devices with wireless communication capabilities, enabling the network to monitor the environment in which it is deployed. Through their flexible and cable-free design these networks open up for new deployment scenarios that were previously not plausible such as during a natural disaster. Motivated by scenarios where centralized oversight is not possible the focus of this thesis is to equip nodes with further adaptability to changes in the links it has with other nodes. This is achieved through contributions in three areas focusing on observations from a node-link perspective. First, the impact the local environment has on the nodes is explored by deploying a sensor network outdoors next to a meteorological station to correlate the variations in link quality to the changes in the environment. The work identifies temperature as the main factor, where through further investigations in a controlled setting, a linear relationship between the decrease in signal quality and the increase in temperature is described. Secondly, the thesis address how nodes in a sensor network can be motivated to exchange data by modeling it as a game. The game theoretic design is motivated by the absence of any centralized control and focus on the nodes as individual users in the network. The presented design motivates the selfish nodes to participate in the exchange of sensor data, showing that it is the best strategy. Lastly, by exploring and understanding how connections in a mobile sensor network occur, nodes are given more flexibility to determine how to send and sample sensor data. This adaptability to contact occurrences is shown to provide better ways of sending data by selecting higher quality links as well as making sampling more energy preserving by reducing the rate in the vicinity of other nodes. / CNDS / WISENET

Deux méthodes expérimentales ont été développées pour mesurer, pour une interface multi-contacts élastomère / verre, les champs mécaniques en volume (micro-capteur de force MEMS noyé sous le film élastique) et à l'interface (imagerie de contact par transmission), résolus spatialement à une échelle intermédiaire entre celle du contact apparent et celle des micro-contacts.<br />La mesure MEMS a permis d'obtenir les champs de contrainte sous charge normale et en glissement stationnaire, en très bon accord avec des modèles mécaniques simples. Pour des substrats de rugosité périodique le lien entre spectre des contraintes et topographie de surface a pu être interprété en termes de filtrage spectral, pertinent pour comprendre la perception tactile.<br />La mesure optique a permis, en analysant la répartition spatiale de l'intensité, d'obtenir le champ de pression de surface. Sa dépendance avec les propriétés de la couche rugueuse a été confrontée au modèle de Greenwood-Tripp. Par suivi des aspérités, le champ de déplacement a été mesuré avec une résolution sub-micronique et a mis en évidence la coexistence de zones glissantes et adhérentes prédite par Cattaneo et Mindlin.