MICRO AND NANO SYSTEMS
The research on MEMS¬†and Microtechnologies started in the mid-90s at IEMN. Now, it has become a federating subject involving several research teams and widely covering topics such as sensors and actuators finding applications in thermal management, fluidic, biology, and nanotechnologies while maintening more fundamental research on thin film materials and actuation modes.
- ¬†Micro and NanoSystems activities (MNS)
Microsystems have a major role to play as to form a continuous nano-micro-meso-macro link and to thus assure the connection between the nanotechnologies and the macroscopic applications by developing a set of consistent and useful functions at the microscopic scale. In this framework, the research effort is focussed on the use of the know-how in macro-actuators and micro-sensors to tackle innovative applications in which the microsystems will interact with nanoscaled objects. The microdevice will either feature a nanometric part, or it will produce or detect displacements or forces of magnitude compatible with the manipulation and characterisation of nano-objects. A recent result concerns the mass fabrication of silicon nanotips with a nanometric apex radius. Carbon nanotubes have been successfully grafted at the apex of the tips with a remarkable yield of 60 %. These nanmetric devices are integrated onto vibrating cantilevers for applications in the field of atomic force microscopy with very high lateral resolution.
- ¬†RF MEMS
IEMN has started this activity on RF MEMS in 1999. At the beginning, the idea was to replace quartz resonators by silicon ones in order to fulfill filter applications in the GHz range and now, the objectives have moved towards lower frequencies, typically in the range of a few tens of MHz where electromechanical resonators can serve as time reference. In collaboration with STMicroelectronics and NXP Semiconductors, devices have been successfully fabricated in industrial facilities with different approaches: above-IC and in-IC. IEMN has also studied Bulk Acoustic Wave ( BAW) filters and proposed original designs that have been patented. Besides resonators activities, RF switches are currently under development for their further integration in MMIC. Together with DELFMEMS Company, a RF switch has been fabricated; it is based on a design less sensitive to temperature variation than widely spread clamped based devices.
- ¬†Microsystems Microfluidics and THz
The investigation of living cells is a very important topic today. This microscopy system contains sophisticated functions as self-reproduction, energetic metabolism or chemical and electrical informative transfer. Our research domain is the observation and the quantification of the biochemical information transfer between the liquid environment of a cell and its progression towards the nucleus.We study the conformational change during this internalization with a new instrumentation based on the THz spectroscopy. This objective is now possible for two principal reasons. On the one hand, the THz photon energy is at the same level of the binding energies inside biomolecules (folding phenomena of proteins for example), and on the other hand, it is possible to obtain a real time measurement (electrical measurement). The technological means for reaching this objective is the design of specific BioMEMS, including planar THz electromagnetic functions coupled with microfluidic circuits. Silicon microtechnology is utilised to form rigid cantilever and mechanical structures for lab on a¬†chip interfaces, notably nanoelectospray emitter tips, such emitter tips are capable of emitting droplets having a diameter of microns or even nanometres. Indeed, we have also recently developed a device which is capable of depositing minuscule¬†volumes (sub-attolitre) of liquid. Characterisation of the devices designed and fabricated at IEMN involves collaboration with the Astbury Centre¬†for Structural Microbiology at the University of Leeds, United Kingdom in order to perform nanoelectrospray ionisation-mass spectrometry (nanoESI-MS). A notable team success is the invention of a novel micromachined nanoelectrospray ionisation tip which has recently been patented and also featured on the front cover of the high impact factor review the Journal of American Society for Mass Spectrometry.
- ¬† Digital microfluidics for biologic applications
EWOD (Electro-Wetting-On-Dielectric) and SAW (Surface-Acoustic-Waves) actuated devices for digital microfluidics devoted to biologic applications. In such a context the droplets are envisioned as mobile laboratories. This point of view allows the making of prototypes for protein analysis by Mass Spectrometry of MALDI type but also the analysis of the behaviour of a single cell under stimuli for which the expressed proteins are potential markers. Moreover the developed devices are thus fitted for a first study on inter-cellular communication within designed networks. Results concerning the realization of a lab-on-chip architecture fitted for EWOD as well as SAW actuation are to be pointed out. A reusable base is dedicated to droplet actuation and guiding while the disposable cover is reserved to the biochemical fictionalizations which allow interaction with the droplet biologic contents i.e. affinity, digestion, concentrating and desalting operations. On going studies are about the use of new nano-textured materials. These materials are to be used in a new generation of Lab-On-Chips for EWOD and SAW transport on a surface with an almost null hysteresis for the making of new integrated targets for Mass Spectrometry without extra matrix but also for the fabrication¬† of functionalised micro-pads with improved yields.
- ¬† Magnetomechanical microsystems (MMMS)
MMMS are micro-systems based on coupled magnetic and mechanical effects. The specificity is to search , or artificially¬† induce, magnetic or mechanical instabilities, in order to improve the performances or add new functionalities to the devices. This activity is a part of the theme entitled “nonlinear magnetoacoustics of condensed matter”. The activity concerns more precisely :
¬§ The elaboration of active magnetic films with induced instabilities of structural or spin reorientation phase transition types. The films are giant magnetostrictive nanostructures as for example N*((TbCo)4,5nm/(FeCo)6,5nm), smart magnetic materials, or magneto-electric films and structures (multiferroics¬†: TbCo/Fe/Co/PZT or TbCo/FeCo/AIN).
¬§ The study of extraordinary nonlinear dynamic magneto-optic and magnetoelastic properties in the vicinity of these instabilities (bistabilities, sub-harmonic excitations…). New techniques of MEMS control were proposed.
¬§ The elaboration of original microsystems based on these films or using electromagnetic ways of control, coupled with mechanical instabilities. The developped microsystems concern micro-actuators, microsensors, and functionnal electronic components : microvalves for microjets (continuous, pulsed, synthetic) and wall microactuators, for the active control of aerodynamic flows for aeronautic or automobile applications, highly integrated arrays of actuators for the reproduction of tactile textures, orientable micro-wave microantennas for communicating MEMS, micro-sensors, in particular integrated to micro-actuators.
- ¬† Heat Flux Microsensors
Heat flux sensors are practically unused in industry and not at all in consumer applications such as electric household appliances, automotive, home automation. This fact is probably due to the ignorance of the advantages related on direct measurement of heat flux or the too higher cost of these sensors for consumer appications. This is why the Micro-Thermics team has developed and patented a new heat flux microsensor entirely produced in silicon technology what makes it possible to manufacture it in very large numbers for a very low price. The structure of these sensors can be considered as a pattern of thermal discontinuity areas realised in the silicon wafer by the way of porous silicon boxes whose thermal conductvity is at least 100 times lower than that of sulk silicon. Consequently, for each area, the incident heat flux is converted into a surface temperature gradient which is converted in e.m.f. by way of a thin doped polysilicon/gold thermopile. By using micromachining, more than 200 cells can be implemented on a 5×5 mm2 microfluxmeter that allows high sensitivity (typically 5 V/W). Furthermore, these sensors induce low disturbances in the thermal environment due to the low thickness and high thermal conductivity of the silicon substrates. Awide variety of applications can be developed such as remote temperature measurement in a dirty environment or the measurement of the evaporation latent heat of liquid drops.