A drop of water thrown on a super-hydrophobic solid will often bounce off. Here we discuss the conditions to be fulfilled on the surface design (which provides superhydrophobicity) to observe such a behavior. This allows us to precise how a material can be made water-repellent. We show in particular how the reduction of the scale of the microstructure provides a robust water repellency, and describe some peculiarities of violent shocks on such surfaces.

This paper presents a novel silicon-based and batch-processed MEMS electrostatic transducer for harvesting and converting the energy of vibrations into electrical energy without using an electret layer. Effective conversion from the mechanical-to-electric domains of 61 nW on a 60 M resistive load, under a vibration level of 0.25 g at 250 Hz, has been demonstrated. Rigorous analysis of the efficiency of the harvester is presented, covering issues related with mechanical and electrical operation. Various schemes for the conditioning electronics are discussed and the harvested power measurements using a dc/dc converter are explained in detail. The paper concludes with a comparison with previous electrostatic transducers based on a new simple factor of merit.

No abstract

No abstract