Abstract: The present invention relates to a balance spring intended to equip a balance of a mechanical timepiece, formed by a spiral bar resulting from machining a fused quartz plate, which has a positive thermal coefficient of rigidity, the bar constituting a core at least locally covered by at least one outer layer having a different structure to modify the thermal coefficient of rigidity.

Abstract: The invention relates to a silicon resonator (10) of the tuning-fork type in which the linear frequency drift depending on the temperature is compensated. The resonator includes a silicon base (14), a plurality of parallel arms (11, 12, 13) capable of vibrating and actuator (18, 21, 22), wherein the arms include a silicon layer provided between two layers of silicon oxide having a thickness, relative to that of the silicon layer, such that it ensures the first-order compensation of the resonator thermal drift.

Abstract: The invention relates to a silicon resonator (10) of the tuning-fork type in which the linear frequency drift depending on the temperature is compensated. The resonator includes a silicon base (14), a plurality of parallel arms (11, 12, 13) capable of vibrating and actuator (18, 21, 22), wherein the arms include a silicon layer provided between two layers of silicon oxide having a thickness, relative to that of the silicon layer, such that it ensures the first-order compensation of the resonator thermal drift.

Abstract: A solid oxide fuel cell structure obtainable by selective electro-chemical processing, comprising an electrolyte membrane (4) formed by a thin film more than 50 nm but less than 10 ?m thick, covering a supporting structure (1) made of a bulk substrate, the supporting structure having at least one 100 ?m to 100 mm wide opening that is covered by the electrolyte membrane (4). A metallic grid (9) is applied over the electrolyte membrane (4) and serves at the same time as structural element to support the membrane and as current collector. The metallic grid (9) has gridlines that are higher than the membrane thickness and whose height to width ratio is larger than 0.5, and a mesh size about 10 to 1000 times smaller than the width of said opening. The metallic grid (9) can be applied on top of a patterned metallic sub-layer structure (7,7a) arranged for supplying a fine distribution of current and increasing the density of electrolyte-electrode boundaries exposed to the fluid.