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Publications de l'équipe MEMS

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34documents trouvés

17186
01/11/2017

In vitro and in vivo biostability assessment of chronically-implanted Parylene C neural sensors

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

Lien : https://hal.laas.fr/hal-01528604

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Abstract

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.

140318
16584
24/10/2017

Probing electrical activity of single neurons based on 1D nanostructures: from extra to intracellular interfacing.

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

Lien : https://hal.laas.fr/hal-01462968

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Abstract

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.

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17140
13/07/2017

Nanoscale boundary conditions and wetting scrutinized at picometer dynamical forcing

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.

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17182
01/06/2017

Deep plasma etching of Parylene C patterns for biomedical applications

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

Lien : https://hal.laas.fr/hal-01528381

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Abstract

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.

140310
17187
25/05/2017

High speed atomic force microscope

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

Lien : https://hal.laas.fr/hal-01529673

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Abstract

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.

140320
16320
01/04/2017

Multi-MHz micro-electro-mechanical sensors for atomic force microscopy

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

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Abstract

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).

139001
16345
01/02/2017

Fabrication of lateral porous silicon membranes for planar microfluidics by means of ion implantation

Y.HE, T.LEICHLE

MEMS

Revue Scientifique : Sensors and Actuators B: Chemical, Vol.239, pp.628-634, Février 2017 , N° 16345

Non disponible

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Abstract

We introduce a new fabrication method based on ion implantation to create lateral porous silicon membranes and integrate them into planar microfluidic devices. Our proposed method relies on the fact that the formation of porous silicon by anodization highly depends on the dopant type and concentration, which can be manipulated by ion implantation. In order to confine the porosification at desired locations within silicon steps bridging microchannels, we use boron and phosphorus implantation to respectively create a p++ layer buried in an n-type silicon substrate, and a protective n-type surficial layer. The use of a metal electrode patterned onto the silicon step for current injection during anodization enables pores to propagate laterally during the membrane formation. The optimal implantation doses and energies leading to the required boron and phosphorus profiles are determined by means of process simulation and further confirmed by SIMS analysis. We demonstrate that the proposed fabrication process leads to the creation of lateral porous silicon membranes with open-ended pores adequately bridging microchannels and that we are able to manipulate the pore size (∼3–30 nm) and membrane porosity (∼15–65%) by adjusting the current density during anodization. The adequate dead-end filtration capability of the fabricated membranes was tested and demonstrates the interest of the presented fabrication process for microfluidic applications.

137837
17002
26/01/2017

Spray-coated carbon nanotube carpets for creeping reduction of conducting polymer based artificial muscles

A.SIMAITE, A.DELAGARDE, B.TONDU, P.SOUERES, E.FLAHAUT, C.BERGAUD

MEMS, ELIA, GEPETTO, CIRIMAT

Revue Scientifique : Nanotechnology, Vol.28, N°2, 025502p., Janvier 2017 , N° 17002

Lien : https://hal.laas.fr/hal-01413022

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Abstract

It is often observed that during cyclic actuation conducting polymer based artificial muscles are continuously creeping from the initial movement range. One of the likely reasons of such behaviour is unbalanced charging during conducting polymer oxidation and reduction. In order to improve the actuation reversibility and subsequently the long time performance of ionic actuators, we suggest to use spray-coated carbon nanotube (CNT) carpets on the surface of the conducting polymer electrodes. We show that carbon nanotubes facilitate conducting polymer redox reaction and improve its reversibility. Consequently, in the long term, charge accumulation in the polymer film is avoided leading to significantly improved long term performance during cycling actuation.

138654
16321
14/12/2016

High spatial resolution imaging of transient thermal events using materials with thermal memory

O.KRAIEVA, C.M.QUINTERO PINZON, I.SULEIMANOV, E.M.HERNANDEZ, D.LAGRANGE, L.SALMON, W.NICOLAZZI, G.MOLNAR, C.BERGAUD, A.BOUSSEKSOU

LCC, I2C, MEMS

Revue Scientifique : Small, Vol.12, N°46, pp.6325-6331, Décembre 2016 , N° 16321

Lien : https://hal.laas.fr/hal-01413097

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Abstract

The accurate control of temperature is a common requirement in science and technology. In particular, although much effort has been devoted in the past decade to the development of nanoscale thermometry methods, we currently lack the tools to map transient thermal events with high spatial resolution. Here we experimentally demonstrate the working principle of a new kind of nanothermometer using materials with thermal memory as time-temperature integrators. As an application, we tackle the outstanding problem of spatially resolving a brusque erratic heating event in an operating microelectronic device. We show that a spatially and temporally confined temperature change leads to a local (reversible) modulation of the optical properties of our material. Thanks to the virtually infinite lifetime of the metastable states within the bistability region, this optical information can be retrieved later on by a simple reflectivity measurement, either in far-or near-field. This concept enabled us to acquire sub-wavelength resolution images of transient (s scale) heating events. The recent tendency of miniaturization and achievements in nanoscience and nanotechnology brought about the necessity of accurate temperature measurements on a reduced size scale [1-4]. In addition, the heat exchange in tiny volumes occurs promptly, hence the measurement needs to be done most often in a limited time window. The lack of spatio-temporal resolution and the increasingly invasive nature of common temperature sensors are the main obstacles 1

138631
16405
05/12/2016

Conception and characterization of flexible microelectrodes for implantable neuroprosthetic development

A.LECOMTE

MEMS

Doctorat : INSA de Toulouse, 5 Décembre 2016, 160p., Président: J.GRISOLIA, Rapporteurs: L.BERDONDINI, G.MALLIARAS, Examinateurs: G.OFFRANC-PIRET, Directeurs de thèse: C.BERGAUD , N° 16405

Lien : https://hal.laas.fr/tel-01417209

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Résumé

Les neuroprothèses sont un domaine de recherche visant à restaurer les fonctions de personnes atteintes de déficiences sensorielles ou motrices. Les implants neuraux assurent une communication bidirectionnelle entre le cerveau et les ordinateurs. Ils permettent par exemple de favoriser la communication et la mobilité des personnes présentant une déficience motrice grave, rétablir la perception sensorielle (vision, audition) et réduire des symptômes neurodégénératifs (Parkinson). Les dernières avancées technologiques et la meilleure compréhension des facteurs déclenchant les réactions inflammatoires permettent d’envisager des implants corticaux chroniques fiables. Les implants traditionnels, basés sur des matériaux rigides comme le silicium ou le tungstène, sont souvent associés à une réaction immunitaire importante, du fait de leur pauvre biocompatibilité et du stress qu'ils induisent sur les tissus environnants. En ce sens, les implants flexibles, basés sur des biomatériaux souples, sont de plus en plus étudiés. Le substrat s'adapte aux micromouvements du cerveau (respiration, pulsation cardiaque) et de se fait promouvoir un meilleur contact tout en diminuant la réaction inflammatoire. Au cours de cette thèse, nous avons conçu et fabriqué un implant flexible à base de Parylène C, polymère souple de plus haute classe de biocompatibilité atteinte par la législation américaine (USP Classe VI), sur lequel des électrodes en or sont positionnées. Divers procédés de la microélectronique, comme la photolithographie et la gravure plasma utilisés communément pour le développement de microsystèmes en métal ou semi-conducteurs, ont été adaptés à la structuration d'implants en Parylène C. Par le biais de la culture cellulaire in vitro, nous avons montré que des cellules neuronales dérivées se différenciaient correctement sur les implants, validant ainsi la biocompatibilité des dispositifs. Cependant, ces nouveaux implants ont tendance à se courber à la surface du cerveau lors de leur insertion, empêchant le bon déroulement de l'implantation. Nous proposons ici une méthode basée sur l'intégration d'un film biorésorbable à l'arrière de l'implant. Ce film rigide permet d'assurer la pénétration de l'implant dans les tissus cérébraux, avant de se dissoudre de façon inoffensive dans l'organisme. Le film est réalisé en fibroïne de soie, extrait des cocons de vers à soie. Ce matériau, plus résistant que le Kevlar, est utilisé depuis des millénaires comme fils de suture biodégradable. La mise au point de l'extraction de la fibroïne de soie et sa structuration sur l'implant à l'aide d'un moule en polymère, ainsi que l’optimisation de la méthode de dépôt permet l'obtention d'une couche de soie en forme de gouttière, ce qui facilite l’insertion tout en limitant les contraintes et pressions indésirables lors de l'insertion. Nous avons montré à travers une série de test in vitro dans des gels et in vivo sur souris, que la soie augmentait par 100 la rigidité de l'implant et pouvait se résorber à taux accordable dans l'organisme. Un aspect primordial des implants neuraux concerne leur tenue et leur fiabilité sur le long terme. Si les implants traditionnels en silicium sont matière à de nombreuses études sur le sujet, les implants en polymères souples ne se sont développés que récemment et ne bénéficient pas encore du même recul. Nous proposons une étude préliminaire in vitro dans du liquide cérébro-spinal artificiel et in vivo sur souris permettant de mettre en évidence l'augmentation de la durée de vie de nos implants. Les résultats ont montré qu'au bout de six mois, les dispositifs ne présentent pas de signe de délamination, corrosion ou gonflement, ce qui se caractérise par la stabilité des propriétés électriques des électrodes. En conclusion, les implants conçus au cours de cette thèse présentent des caractéristiques prometteuses pour le développement de neuroprothèses implantables flexibles fiables sur le long terme.

Mots-Clés / Keywords
Biomatériaux; Implantation chronique; Neuroprothèse; Polymère flexible;

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