Hussein Nesser

Electrostriction as an integrated transduction method for organic MEMS

Electrostriction is based on the variation of permittivity of a dielectric material when subjected to mechanical strain. Until now, the use of electrostrictive materials is limited to the actuation of Micro Electro Mechanical Systems (MEMS) operating mostly in static mode. Here, we present the use of electrostriction as integrated transduction scheme in organic microcantilevers operating in both static and dynamic modes. Also, an innovative low-cost and environment friendly process using xurography is developed for the simple fabrication of MEMS in an all-organic approach. Electromechanical characterization of the organic microcantilevers is performed with the aim of validating this new concept using an original composite material based on functionalized graphene oxide (GO) dispersed in a polydimethylsiloxane (PDMS) elastomer. This material is characterized by a dielectric permittivity thousand times larger than that of pure PDMS. The electrostrictive composite shows good performances when the microcantilever is bent, with a variation of capacitance exceeding 4 % for low strain values (<; 1 %). Also, the integrated electrical detection of the microcantilevers resonant frequency (≤ 300 Hz) makes these devices suitable for mechanical energy harvesting. Trapezoidal shaped microcantilevers incorporating a seismic mass at its end give the best results with a resonant frequency of ~ 15 Hz and electromechanical performance 100 times greater than that of rectangular ones.

Organic microcantilevers based on reduced graphene oxide composite for electrostrictive energy harvesting

Electrostrictive materials are promising for mechanical energy harvesting applications because of their high power density, low cost and scalability. In this paper, strain sensitive nanocomposite materials based on reduced graphene (rGO) and PDMS are used for energy harvesting; they are characterized by a high electrostrictive coefficient (2.4x10-15 m2/V2) and a giant dielectric constant (ranging from 100 to 1000 at 100 Hz, depending of rGO concentration). Using these nanocomposite materials, electrostrictive MEMS microgenerators are fabricated with an innovative low-cost and environment friendly process in an all-organic approach. The fabricated microcantilevers exhibit excellent mechanoelectrical performances in dynamic mode. With an acceleration of 1 g of the microcantilever base using a shaker, experiment at the first resonant mode (≈ 16 Hz) generates an electrical power density of 8.15 μW/cm3.