Laboratoire d’analyse et d’architecture des systèmes
H.RANCHON, J.CACHEUX, B.REIG, O.LIOT, P.TEERAPANICH, T.LEICHLE, P.JOSEPH, A.BANCAUD
MILE, MEMS, TEAM
Revue Scientifique : Langmuir, Vol.34, N°4, pp.1394-1399, Janvier 2018 , N° 18012
We investigate the pressure-driven transport of particles 200 or 300 nm in diameter in shallow microfluidic channels ∼1 μm in height with a bottom wall characterized by a high roughness amplitude of ∼100 nm. This study starts with the description of an assay to generate cracks in hydrophilic thin polymer films together with a structural characterization of these corrugations. Microfluidic chips of variable height are then assembled on top of these rough surfaces, and the transport of particles is assessed by measuring the velocity distribution function for a set of pressure drops. We specifically detect anomalous transport properties for rough surfaces. The maximum particle velocity at the centerline of the channel is comparable to that obtained with smooth surfaces, but the average particle velocity increases nonlinearly with the flow rate. We suggest that the change in the boundary condition at the rough wall is not sufficient to account for our data and that the occurrence of contacts between the particle and the surface transports the particle away from the wall and speeds up its motion. We finally draw perspectives for the separation by field-flow fractionation.
A.LECOMTE, A.DEGACHE, E.DESCAMPS, L.DAHAN, C.BERGAUD
MEMS, IMS Bordeaux, CRCA
Revue Scientifique : Sensors and Actuators B: Chemical, Vol.251, pp.1001-1008, Novembre 2017 , N° 17186
Parylene C has rapidly gained attention as a exible biomaterial for a new generation of chronic neural probes. However, polymeric material failure in the form of delamination, swelling or tearing, often compromises device biostability in the long term. This work constitutes a rst step towards lifetime assessment of Parylene C implanted devices. We have conceived a Parylene C-based neural probe with PEDOT-nanostructured gold electrodes for the recording of brain activity. The material response to its biological environment was studied through in vitro soaking tests and in vivo wireless recordings in mice brain, both carried out for up to 6 months. Impedance monitoring and SEM images indicate that over the length of this trial, none of the implants presented with apparent signs of material degradation. Packaging reliability was a predominant factor in device failure, with a certain number of faulty connection appearing over time. This parameter aside, all soaked devices were stable in Articial Cerebro-Spinal Fluid, with impedances within 10% of their initial value after 6 months at 37°C. Besides, at least 70% of the implanted device were able to accurately record wirelessly high amplitude hippocampal Local Field Potentials from freely-moving mice, with steady Signal-to-Noise Ratio. In other terms, Parylene C implantable sensors responded minimally to articial and actual physiological conditions during a period of 6 months, which makes them promising candidates for reliable, chronically implanted sensors in the biomedical eld.
A.CASANOVA, MC.BLATCHE, F.MATHIEU, A.LECESTRE, C.FERRE, D.GONZALES DUNIA, L.NICU, G.LARRIEU
MPN, I2C, TEAM, INSERM, EXT, MEMS
Manifestation avec acte : IEEE Nanotechnology Materials and Devices Conference ( IEEE NMDC ) 2016 du 09 octobre au 12 octobre 2016, Toulouse (France), Octobre 2017, 2p. , N° 16584
The struggle against neurodegenerative diseases is one of the major challenges in the near future and the global understanding of these diseases goes through a better expertise at the single cell level of basic mechanisms involved in neuronal networks. We need to investigate closer to the cellular material and in this way, miniaturization of electronic components and emergence of nano-biotechnology open new perspectives. Indeed, we are now able to fabricate high sensitive nano-devices to follow neuronal activities. Here, we will present two different approaches to interface neurons, a first one based on a nano-FET for extracellular recordings and a second one using vertical nanowire arrays (nano-electrodes) for intracellular measurements.
N. S.HABTOUN, S.HOUMADI, B.REIG, E.POUGET, D.DEDOVET, M.H.DELVILLE, R.ODA, F.CRISTIANO, C.BERGAUD
MEMS, NBS, TEAM, CBMN, ICMCB-CNRS, MPN
Revue Scientifique : Materials Research Express, Vol.4, N°10, 105023p., Octobre 2017 , N° 17439
Silica nanosprings (NS) are fabricated by a sol–gel deposition of silica precursors onto a template made of self-assembled organic chiral nanostructures. They are deposited and assembled on microstructured silicon substrates, and then metallized and clamped in a single lithography-free step using a focused ion beam (FIB). The resulting suspended hybrid metallic/inorganic NS are then characterized with high-resolution transmission electron microscopy (HRTEM) and scanning TEM/energy-dispersive X-ray spectroscopy (STEM/EDX), showing the atomic structure of the metallic layer. Three-point bending tests are also carried out using an atomic force microscope (AFM) and supported by finite element method (FEM) simulation with COMSOL Multiphysics allowing the characterization of the mechanical behavior and the estimation of the stiffness of the resulting NS. The information obtained on the structural and mechanical properties of the NS is discussed for future nano-electro-mechanical system (NEMS) applications.
J.P.AIME, J.P.SALVETAT, M.FAUCHER, T.ONDARCUHU, D.THERON, B.LEGRAND
IECB, CRPP, Pessac, IEMN Villeneuve, CEMES/CNRS, MEMS
Rapport LAAS N°17140, Juillet 2017, 15p.
M.DMANRIQUE JUAREZ, F.MATHIEU, V.SHALABAEVA, J.CACHEUX, S.RAT, L.NICU, T.LEICHLE, L.SALMON, G.MOLNAR, A.BOUSSEKSOU
MEMS, I2C, LCC
Revue Scientifique : Angewandte Chemie International Edition, Vol.56, N°28, pp.8074-8078, Juillet 2017 , N° 17501
We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)3)2] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex. The strong mechanical coupling was also evidenced by the decrease of approximately 66 Hz in the resonance frequency in the high-spin state as well as by the drop in the quality factor around the spin transition.
A.LECOMTE, A.LECESTRE, D.BOURRIER, MC.BLATCHE, L.JALABERT, E.DESCAMPS, C.BERGAUD
MEMS, TEAM, I2C
Revue Scientifique : Microelectronic Engineering, Vol.177, pp.70-73, Juin 2017 , N° 17182
We report on the plasma etching of thick (~23µm) Parylene C structures. Parylene C is a transparent polymer that benefits from high biocompatibility, flexibility and chemical inertness, and has gained increased attention over the years in the biomedical field. In the manufacturing process, highly defined structuration steps of Parylene C are essential, but techniques based on laser, scalpel and wet etching have shown to be unsuitable for properly cut structures. Plasma etching remains nowadays the most widespread option, though fast etching rate, lack of residues and high aspect ratios are still hard to achieve. To overcome these issues, the selection of both mask material and plasma conditions is crucial. Here, three masks-metal, positive and negative photoresists-are tested as stencils, and several plasma parameters are briefly studied in order to obtain the highest etching rate while maintaining good coverage. We showed that increasing the RF power up to a considerable 2800W while maintaining a moderate physical contribution (bias power, pressure, temperature), is optimal in the achievement of fast PaC etching without inducing thermal stress. Besides, the addition of a short fluorinated plasma in the midst of the process is shown to alleviate residues. For the first time, negative photoresist Intervia Bump Plating (BPN) coating followed by ICP 1-RIE 2 are used in order to pattern Parylene C-based structures, with a clean cut, vertical profile and fast etching rate (~0.87±0.06 µm/min) and a selectivity of 0.5. This solution was carried out to release unitary Parylene-based neural probes from a silicon wafer. Finally, cytotoxicity assays on these neural implants were performed to make sure that no trace of mask or stripper residues would jeopardize device biocompatibility.
N.MAURAN, D.LAGRANGE, X.DOLLAT, L.MAZENQ, L.SCHWAB, J.P.SALVETAT, B.LEGRAND
I2C, TEAM, MEMS, CRPP, Pessac
Affiche/Poster : NIWeek ( ) 2017 du 22 mai au 25 mai 2017, Austin (USA), Mai 2017, 1p. , N° 17187
Atomic Force Microscope (AFM) is now a common tool for material analysis in the academic and industrial areas because it enables non-destructive high-resolution images of nanometric objects. However, a main drawback is the slow scan rate that hinders many potential applications. Recently, breakthroughs have been achieved in AFM sensors based on MEMS technology, allowing to extend AFM operation in terms of measurement bandwidth and data acquisition. The present work focusses on developing an electronic controller for AFM featuring the wide bandwidth and the fast data processing rate required to enable the exploitation of the full potential of MEMS AFM sensors.
B.LEGRAND, J.P.SALVETAT, B.WALTER, M.FAUCHER, D.THERON, J.P.AIME
MEMS, CRPP, Pessac, IEMN Villeneuve, CBMN
Revue Scientifique : Ultramicroscopy, Vol.175, pp.46-57, Avril 2017 , N° 16320
Silicon ring-shaped micro-electro-mechanical resonators have been fabricated and used as probes for dynamic atomic force microscopy (AFM) experiments. They offer resotnance frequency above 10 MHz, which is notably greater than that of usual cantilevers and quartz-based AFM probes. On-chip electrical actuation and readout of the tip oscillation are obtained by means of built-in capacitive transducers. Displacement and force resolutions have been determined from noise analysis at 1.5 fm/√Hz and 0.4 pN/√Hz, respectively. Despite the high effective stiffness of the probes, the tip-surface interaction force is kept below 1 nN by using vibration amplitude significantly below 100 pm and setpoint close to the free vibration conditions. Imaging capabilities in amplitude- and frequency-modulation AFM modes have been demonstrated on block copolymer surfaces. Z-spectroscopy experiments revealed that the tip is vibrating in permanent contact with the viscoelastic material, with a pinned contact line. Results are compared to those obtained with commercial AFM cantilevers driven at large amplitudes (>10 nm).
A.WELSH, D.DEZEST, L.NICU, S.TROLIER-MCKINSTRY
Revue Scientifique : Journal of the American Ceramic Society, Vol.100, N°3, pp.848-858, Mars 2017 , N° 17499
The functional properties of electroceramic thin films can be degraded by subtractive patterning techniques used for microelectromechanical (MEMS) applications. This work explores an alternative deposition technique, where lead zirconate titanate (PZT) liquid precursors are printed onto substrates in a desired geometry from stamp wells (rather than stamp protrusions). Printing from wells significantly increased sidewall angles (from ~1 to >35 degrees) relative to printing solutions from stamp protrusions. Arrays of PZT features were printed, characterized, and compared to continuous PZT thin films of similar thickness. Three-hundred-nanometer-thick printed PZT features exhibit a permittivity of 730 and a loss tangent of 0.022. The features showed remanent polarizations of 26 μC/cm2, and coercive fields of 95 kV/cm. The piezoelectric response of the features produced an e31,f of −5.2 C/m2. This technique was also used to print directly atop prepatterned substrates. Optimization of printing parameters yielded patterned films with 90° sidewalls. Lateral feature sizes ranged from hundreds of micrometers down to one micrometer. In addition, several device designs were prepatterned onto silicon on insulator (SOI) wafers (Si/SiO2/Si with thicknesses of 0.35/1/500 μm). The top patterned silicon was released from the underlying material, and PZT was directly printed and crystallized on the free-standing structures.