Showing papers by "Elie Lefeuvre published in 2010"

Towards high fidelity high efficiency MEMS microspeakers

Abstract: This paper presents simulations and microfabrication of different parts of high fidelity electrodynamic MEMS loudspeakers with high electroacoustic conversion efficiency. The originality of the structure lies on the use of rigid silicon membranes suspended by a whole set of silicon beams instead of flexible polymer membranes usually found in MEMS loudspeakers. The microspeaker structure includes a planar copper microcoil electroplated on the silicon membrane and permanent magnets bonded on the substrate. Microstructure of the silicon membrane was optimized using FEM simulations for providing both rigidity and lightness of the mobile part. The results presented on a deep RIE etched 15 mm diameter silicon membrane structured with 40 stiffening ribs and on a 30 µm thick microcoil with 35 turns experimentally show the feasibility of key stages required for manufacturing of MEMS microspeakers with outstanding properties.

Piezoelectric Material-Based Energy Harvesting Devices: Advance of SSH Optimization Techniques (1999-2009)

Abstract: This chapter focuses on piezoelectrics, whose use for the purpose of generating electricity is actually not a recent idea (McLean Nicolson A., 1931). Piezoelectric materials have high power densities, but setting up large amount of these materials for high power applications is technically difficult. Consequently, they cannot compete with electromagnetic devices for most of usual applications of electrical energy production. Nonetheless, piezoelectric materials have recently encountered renewed interest for miniaturized energy harvesting devices from ambient vibrations. Drastic increase of international research efforts has been observed since last ten years in this field (Anton et al., 2007), and commercial products are becoming available (Energy Harvesting Forum (Online)). Such energy harvesting devices aim at replacing batteries in very low power electronic devices such as wireless sensors networks and control systems. Their use for recharging batteries of mobile electronic devices is also under development (Krikke, 2005). Maintenance free, self-powered devices for their lifetime has become an industrial objective for the next few years. However, there are further mountains to climb from self-powered devices become commonplace.

MEMS Process by Film Transfer Using Fluorocarbon Anti-Adhesive Layer

Abstract: A low cost and low temperature microelectromechanical systems (MEMS) transfer process is presented. The process is based on adhesion control of molded electroplated Ni microstructures on the donor wafer by using a plasma deposited fluorocarbon film. Adhesive bonding of the microstructures on the target wafer using BCB sealing enables mechanical tearing off from the donor wafer. This proposed process has allowed us to realize from 7 � m down to 700 nm thick Ni patterns on Si, Pyrex glass wafers and Kapton foils. Multiple transfers lead to Ni stacked microstructures. We demonstrated the interest of a simple film transfer process for the elaboration of 3D microstructures.