Next generation of astronomical instrumentation for space telescopes requires Micro-Opto-Electro- Mechanical Systems (MOEMS) with remote control capability and cryogenic operation. MOEMS devices have the capability to tailor the incoming light in terms of intensity and object selection with programmable slit masks, in terms of phase and wavefront control with micro-deformable mirrors, and finally in terms of spectrum with programmable diffraction gratings. Applications are multi-object spectroscopy (MOS), wavefront correction and programmable spectrographs. We are engaged since several years in the design, realization and characterization of MOEMS devices suited for astronomical instrumentation.
Based on the micro-electronics fabrication process, Micro-Opto-Electro-Mechanical Systems (MOEMS) are under study in order to be integrated in next-generation astronomical instruments for ground-based and space telescopes. Their main advantages are their compactness, scalability, specific task customization using elementary building blocks, and remote control. At Laboratoire d’Astrophysique de Marseille, we are engaged since several years in the design, realization and characterization of programmable slit masks for multi-object spectroscopy and micro-deformable mirrors for wavefront correction. First prototypes have been developed and show results matching with the requirements.
Zinc oxide is used in many applications thanks to its various characteristics as well as photoresistivity, piezoelectricity,
wide band gap for power components but also its capability for gas detection. In this article, we first present new process
based on ZnO nanoparticles from Sigma Aldrich manufacturer; a stable ink obtained by mixing 10% weight of
commercial powder with ethylene glycol, has been deposited by ink-jet printing on a silicon oxide substrate covered by
platinum interdigitated electrodes. To obtain homogeneous deposits of nanoparticles, the working area of the sensor was
bounded by functionalisation by the n-Octadecyltrichlorosilane. These deposits were optimized at 65°C.
Then, the study was focused on the correlation between parameters of deposit and global resistance and gas sensitivity:
conductivity for different operating temperatures under methane and isopropyl alcohol vapours. The best results have
been obtained for thicknesses in the range of 0.5 and 2.5 μm. The ZnO resistance is stable under gas from 200°C and the
relative sensitivity to methane and isopropyl alcohol are maximum and opposite at 225°C and 300°C respectively. This
work shows that ink-jet is a promising technique to manufacture a new generation of low cost gas sensors at lower
temperature deposition.
Future adaptive optics (AO) systems require deformable mirrors with very challenging parameters, up to 250 000
actuators and inter-actuator spacing around 500 &mgr;m. MOEMS-based devices are promising for the development of a
complete generation of new deformable mirrors. Our micro-deformable mirror (MDM) is based on an array of
electrostatic actuators with attachments to a continuous mirror on top. The originality of our approach lies in the
elaboration of layers made of polymer materials. Mirror layers and active actuators have been demonstrated. Based on
the design of this actuator and our polymer process, realization of a complete polymer-MDM has been done using two
process flows: the first involves exclusively polymer materials while the second uses SU8 polymer for structural layers
and SiO2 and sol-gel for sacrificial layers. The latest shows a better capability in order to produce completely released
structures.
The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then,
we have developed a dedicated 14-bit electronics in order to "linearize" the actuation, using a calibration and a sixth-order
polynomial fitting strategy. The response is nearly perfect over our 3×3 MDM prototype with a standard deviation
of 3.5 nm; the influence function of the central actuator has been measured. First evaluation on the cross non-linarities
has also been studied on OKO mirror and a simple look-up table is sufficient for determining the location of each
actuator whatever the locations of the neighbor actuators.
Electrostatic MDM are particularly well suited for open-loop AO applications.
Next generation adaptive optical (AO) systems require deformable mirrors with very challenging parameters, up to
250 000 actuators and inter-actuator spacing around 500μm. MOEMS-based devices are promising for the development
of a complete generation of new deformable mirrors. We are currently developing a micro-deformable mirror (MDM)
based on an array of electrostatic actuators with attachments to a continuous mirror on top. The originality of our
approach lies in the elaboration of layers made of polymer materials. Mirrors with very efficient planarization and
active actuators have been demonstrated, with a piston motion of 2μm for 30V. Using our dedicated characterization
bench, we have measured a 6.5kHz resonance frequency, well suited for AO applications. Based on the design of this
actuator and our polymer process, realization of a complete polymer-MDM is under way.
The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then,
we have developed a dedicated 14-bit electronics in order to "linearize" the actuation. After calibrating the behavior of
each actuator and fitting the curve by a sixth order polynomial, the electronics delivers a linearized output. The response
is nearly perfect over our 3×3 MDM prototype with a standard deviation of 3.5 nm, and we have then obtained the
influence function of the central actuator. First evaluation on the cross non-linarities has also been evaluated on the
OKO mirror and a simple look-up table is sufficient for determining the location of each actuator whatever the locations
of the neighbor actuators. Electrostatic MDM are particularly well suited for AO applications.
Highly performing adaptive optical (AO) systems are mandatory for next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes, for studying new fields like circumstellar disks and extra-solar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. We are currently developing a micro-deformable mirror (MDM) based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. In order to reach large stroke for low driving voltage, the originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials. We have developed the first polymer piston-motion actuator: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V, and measured resonance frequency of 6.5kHz is well suited for AO systems. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. We have successfully developed a dedicated 14-bit electronics in order to "linearize" the actuation. Actual location of the actuator versus expected location of the actuator is obtained with a standard deviation of 21 nm. Comparison with FEM models shows very good agreement, and design of a complete polymer-based MDM has been done.
Next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes relies on the availability of highly performing adaptive optical systems, for studying new fields like circumstellar disks and extrasolar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. However, only limited strokes for large driving voltages have been demonstrated. In order to overcome these limitations, we are currently developing a micro-deformable mirror based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. The originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials, using low-temperature process. This process allows the realization of high optical quality mirrors on top of an actuator array made with various techniques. We have developed the first polymer piston-motion actuator in order to reach high strokes for low driving voltages: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V. Preliminary comparison with FEM models show very good agreement and design of a complete polymer-based MDM looks possible.
The market of portable instruments is growing more and more. For applications such as computers, cellular phones and microsystems, it is essential to reduce size and weight of electronic devices, including power unit supplies associated with these products. This evolution will require high efficiency on-chip DC-DC converters providing low voltage for the various Ics. Therefore, fabrication of magnetic components dedicated to power conversion becomes necessary. To miniaturize inductors, the micromachining techniques provide solutions based on low-temperature process compatible with active part of the converter. In this paper, a "spiral type" inductor topology designed for power electronics application is investigated. Thick resist molds photolithography and electroplating techniques are used to achieve the copper conductor and the NiFe laminated magnetic core.
Next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes relies on the availability of highly performing adaptive optical systems. Different types of AO systems are currently under study, including Multi-Conjugate AO (MCAO), high dynamic range AO, and low-order AO for distributed partial correction AO. These systems require a large variety of deformable mirrors with very challenging parameters. The development of new technologies based on micro-opto-electro-mechanical systems (MOEMS) is promising for future deformable mirrors. The major advantages of the micro-deformable mirrors (MDM) are their compactness, scalability, and specific task customization using elementary building blocks. We are currently developing a MDM based on an array of electrostatic actuators with attachments to a continuous mirror on top. A high optical quality mirror is the most challenging building block for this device. The originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials. With this structure, very efficient planarization has been obtained: the long-distance flatness is below 0.2 μm, the print-through of localized 9μm steps is reduced to below 0.5μm and a rms roughness of 15 nm has been measured over the surface. The integration of this mirror surface on top of an actuator array is under investigation.
With the development of microspacecraft technology micropropulsion concepts are introduce for course correction, orbit insertion as well as attitude control of the microspacecraft. In this context, we have introduced a new concept of MEMS based technology microthruster responding to the spatial constraints and MEMS characteristics. The originality and advantages of these new thrusters is the use of only one solid propellant stored in a small tank micromachined in a ceramic or silicon substrate and the possibility of fabricating arrays of N addressable independently microthrusters in the same chip. The thrust force generated can be set from a few (mu) N to a few 150mN by geometrical and dimensional considerations. Fabrication and assembly of array of 16 microthrusters proved the technological feasibility and the functioning performances of this new concept of small scale thrusters.
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