Micro/nano/biosystems, waves and microfluidics
Launched in the mid-1990s, research on Micro and Nano Systems at the IEMN is currently experiencing significant growth with the increasing involvement of several research groups covering sensor and actuator aspects with applications in fluidics, biology, thermics, and nanotechnology, while maintaining a conceptual research activity in materials and actuation modes.
Underpinned by modelling work whose aim is to understand the physical phenomena involved, the presentation of the research activities of the MNS axis conducted over the last four years can be illustrated by the following actions:
Vibrating MNS for atomic force microscopy
One of the major challenges for microsystems in the coming years is to place themselves at the interface between nanotechnologies and the macroscopic world. The microsystem can then itself possess organs at the nanometric scale, or it can produce and measure displacements or forces compatible with the manipulation and characterization of nano-objects. A recent result concerns the collective fabrication of silicon nanopoints, whose radius of curvature at the apex is a few tens of nanometers and on which the grafting of carbon nanotubes has been obtained with a remarkable yield of 60%. These objects are then integrated into vibrating levers for near-field microscopy applications at very high lateral resolution.
RF MEMS: electro-mechanical resonators
Following on from work undertaken in 1999, the results acquired recently place the IEMN among the reference laboratories working on electro-mechanical resonators intended for communication systems. Over the last few years, the application objectives have evolved from filtering to time reference, resulting in a reduction in the frequency range targeted, which is now established at a few tens of MHz, compared to one GHz four years ago. In collaboration with STMicroelectronics or NXP Semiconductors, devices manufactured in industrial channels have made it possible to explore "in-IC" and "above-IC" approaches.
The objective is to study the conformational changes of proteins using a new instrumentation based on THz spectroscopy. A first research axis concerns the establishment of specific THz signatures of protein solutions. A second axis aims at the definition of a THz microscopy based on the Goubau line propagation. Recently, the excellent propagation around nanometer sized wires has been demonstrated. These technological orientations allow to obtain the good spatio-temporal resolution necessary for the cellular examination.
Electrospray microsources for proteomics
Mass spectrometry benefits from the work carried out on micro electrospray sources. Indeed, if the gain in size is not of several orders of magnitude, the ionization yield is considerably increased thanks to a patented design of sources whose manufacture is compatible with a "top-down" technology. The glass capillary traditionally used is replaced by a silicon micro capillary slit allowing to reduce the electric field while increasing the signal to noise ratio during the spectrometric analysis.
The drops are considered as mobile micro laboratories. This point of view allows the realization of prototypes for the analysis of proteins by MALDI-MS but also for the analysis of the behavior of a single cell under stimuli for which the expressed proteins are potential markers. Moreover, the devices developed are suitable for the study of intercellular communication in pre-organized networks.
Magneto mechanical microsystems
MMMS are microsystems based on coupled magnetic and mechanical effects. The specificity is to search for, or to induce voluntarily, magnetic or mechanical instabilities in the devices, in order to improve their performances or to provide new functionalities. The activity focuses on the elaboration of active magnetic films with induced instabilities such as structural phase transitions or spin reorientation, as well as on the elaboration of original microsystems based on these films or using electromagnetic controls coupled to mechanical instabilities.
The IEMN has developed and patented a thermal flux micro-sensor entirely made of silicon technology which allows to manufacture it in very large series for a very low price. The structure of these sensors can be considered as a matrix of cells with thermal discontinuities made in the wafer in the form of porous silicon boxes whose thermal conductivity is at least 100 times lower than that of solid silicon. Consequently, for each of these zones, the incident heat flow is converted into a surface temperature gradient and then into voltage using a doped polysilicon thermopile. Using this technology, more than 200 cells can easily be realized on a 5×5 mm² microfluxmeter, with a very high sensitivity (typically 5 V/W) for a sensor of this surface.