The design of ultra-low power micro-hotplates on a polyimide (PI) substrate supported by thermal simulations and characterization is presented. By establishing a method for the thermal simulation of very small scale heating elements, the goal of this study was to decrease the power consumption of PI micro-hotplates to a few milliwatts to make them suitable for very low power applications. To this end, the mean heat transfer coefficients in air of the devices were extracted by finite element analysis combined with very precise thermographic measurements. A simulation model was implemented for these hotplates to investigate both the influence of their downscaling and the bulk micromachining of the polyimide substrate to lower their power consumptions. Simulations were in very good agreement with the experimental results. The main parameters influencing significantly the power consumption at such dimensions were identified and guidelines were defined allowing the design of very small (15 × 15 μm) and ultra-low power heating elements (6 mW at 300 • C). These very low power heating structures enable the realization of flexible sensors, such as gas, flow or wind sensors, for applications in autonomous wireless sensors networks or RFID applications and make them compatible with large-scale production on foil such as roll-to-roll or printing processes.

In multi-object spectrometers, field selectors, which are located in the focal plane of the telescopes, are required for the selection of astronomical objects, such as stars or faint galaxies. We present a two-dimensional micromirror array as a field selector. Object selection is achieved through the precise tilting of micromirrors, which reflect the light of objects toward the spectrometer. These arrays were composed of 2048 (32 × 64) electrostatically actuated silicon micromirrors that measured 100 × 200 μm 2 . The micromirrors were addressed either by lines or individually using a line-column addressing scheme. The fabrication process of these devices involved three wafers and two wafer-level bondings. Characterization, by white light interferometry, revealed a tilt angle of 25 • at a voltage of 121 V, and a coated micromirror deformation below 10 nm. A fill factor of 82% and a contrast of 1000:1 were also observed. Demonstration of the line-column addressing scheme was achieved through its application to a sub-array of 2 × 2 micromirrors.

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