- [Show abstract] [Hide abstract] ABSTRACT: The BPN is a negative photoresist, sensitive in the UV at 365 nm and was previously dedicated for Wafer Level Packaging applications. This photoresist offers the advantage of forming thick layers; however, it suffers from low aspect ratio (2:1 declared by the supplier). This work reports the BPN’s technological process that allows forming 200–800 μm thick molds for electroplating purposes. Our results revealed an aspect ratio as high as 17:1 while having vertical sidewalls using conventional photolithography.
- [Show abstract] [Hide abstract] ABSTRACT: The BPN is a negative photoresist, sensitive in the UV at 365 nm and was previously dedicated for Wafer Level Packaging (WLP) applications. This photoresist offer the advantage of forming thick layers, however, it suffers from low aspect ratio (2:1 declared by the supplier). This work reports the optimization of BPN’s technological process enabling forming 30–160 μm thick molds for electroplating purposes. Our results revealed an aspect ratio as high as 16:1 while having vertical sidewalls using conventional photolithography.
- [Show abstract] [Hide abstract] ABSTRACT: single molecule level of proteins exhibiting mechanical stability poses a technical challenge that has been almost exclu-sively approached by atomic force microscopy (AFM) techniques. However, due to mechanical drift limitations, AFM techniques are restricted to experi-mental recordings that last less than a minute in the high-force regime. Here we demonstrate a novel combination of electromagnetic tweezers and evanes-cent nanometry that readily captures the forced unfolding trajectories of protein L at pulling forces as low as 10~15 pN. Using this approach, we monitor un-folding and refolding cycles of the same polyprotein for a period of time longer than 30 minutes. From such long lasting recordings, we obtain ensemble aver-ages of unfolding step sizes and rates that are consistent with single molecule AFM data obtained at higher stretching forces. The unfolding kinetics of pro-tein L at low stretching forces confirms and extends the observations that the mechanical unfolding rate is exponentially dependent on the pulling force within a wide range of stretching forces spanning from 13 pN up to 120 pN, thereby excluding the presence of curvature in the rate-versus-force plot. Our experiments demonstrate a novel approach for the mechanical manipulation of single proteins for extended periods of time in the low-force regime, provid-ing an ideal complement to force-clamp AFM, expanding the accessible re-gions of the unfolding energy landscape of a mechanically stable protein.. Helical duplex DNA continually experiences torque from translocating macro-molecular complexes and helix unwinding proteins. We have developed a mag-netic tweezers methodology using a cylindrical magnet and magnetic nanorods to directly measure torsional stress, or resistive torque, as twists are introduced at low pulling forces. We demonstrate the utility of this method by measuring the resistive torque of single DNA molecules and, for the first time, single chro-matin fibers. Figure: New and conventional magnetic tweezers configurations. (a) In con-ventional magnetic tweezers, the field orients the induced dipole of the super-paramagnetic bead horizontally, producing a strong horizontal angular trap that prevents angular fluctuations of the probe. (b) In the new configuration consist-ing of a vertical magnetic field and nanorod-bead construct, the magnetic field and the probe dipole align vertically, thus horizontal angular movements are not constrained. A weak horizontal force generates a weak horizontal angular trap allowing us to measure the torque applied to the molecule. (c) Scanning electron micrograph of magnetic Ni-Pt nanorods (bar ¼ 1mm). (d) Bright-field image of nanorod-bead probe. Nanorod and bead self-assemble by magnetic at-traction.
- [Show abstract] [Hide abstract] ABSTRACT: The integration of passive components on silicon for future dc-dc converter applications is still a challenging area of research. This paper reports the microfabrication of a fully integrated filter containing a spiral inductor on top of a 3-D capacitor. A thin magnetic shielding layer is introduced between the two components demonstrating that losses caused by the inductor in the capacitor area are reduced, thus increasing the maximum working frequency of the whole component. The fabricated filter was characterized in a test circuit (buck-type converter).
- [Show abstract] [Hide abstract] ABSTRACT: This paper reviews our works about the development of thin composite film based on aligned carbon nanotubes (CNT) forest, embedded in epoxy or PMMA polymer matrix, in order to fabricate membranes dedicated to water purification issue. Indeed, the small internal radius of nanotubes, the smoothness of their inner core and the hydrophobic properties of its interna surface induce remarkable flowing properties for water molecules. In this article, thinnin technology process is investigated to obtain composite film with opened CNT. Different etching techniques as grinding, Chemical Mechanical Polishing (CMP) and isotropic plasma O2ar investigated in term of etching rate and membrane roughness, using AFM and SEM characterizations. Results show CMP process in lapping configuration permits to obtain agreement between high etching rate and membrane roughness. Moreover, to improve water flowing through membrane, O2plasma treatment is used to remove polymer residue spread over CNT. Joint use of lapping and plasma treatment permits to obtain 35μm-thick nanoporous membrane with well-opened protruding nanotubes.
- [Show abstract] [Hide abstract] ABSTRACT: This work deals with recent advances in the microfabrication process technology for medium to high-aspect ratio structures fabricated by UV photolithography using different kinds of photoresists. The resulting structures were used as molds and will be transformed into metal structures by electroplating. Two types of photoresists are compared: epoxy-based (negative) SU-8 and acrylate-based (negative) Intervia BPN. This work was prompted by the need to find an alternative to SU-8 photoresist which is difficult to process and remove after electroplating. The results presented in this paper open up new possibilities for low-cost processes using electroplating in MEMS applications.
- [Show abstract] [Hide abstract] ABSTRACT: The objective of the present work is to investigate experimentally the deposition of micron-sized particles onto the surface of a microsieve membrane, which consists in a thin screen with patterned circular holes. A dilute suspension of spherical, monodisperse, polystyrene particles flows at an imposed flow rate through the membrane, in a frontal filtration mode i.e., the flow direction is perpendicular to the membrane. The particle-to-pore diameter ratio is inferior to one. The particle and flow Reynolds numbers are both smaller than 0.1 for the flow regimes investigated in the present study. The particles are non-Brownian, inertialess, and their buoyancy is negligible. Direct visualizations of the membrane are made using video microscopy. A statistical analysis of the particle deposition locations, based on an automatic processing of video images of the membrane surface recorded during the experiment, is made possible by the periodicity of the pore distribution. Experiments show the existence of two preferential locations for particle deposition, for the whole range of flow rates investigated in the present study and the three microsieve patterns used. This puzzling result is discussed in the light of earlier theoretical and numerical simulations works, dealing with the low Reynolds number motion of a single particle in the vicinity of a pore, in the presence of physicochemical interactions between the particle and the membrane surface.
- [Show abstract] [Hide abstract] ABSTRACT: This paper deals with the development of a micro-interconnection technology suitable for the elaboration of RF-NEMS (Nano-ElectroMechanical Systems) varactors. It aims to present an extension of RF MEMS concept into nano-scale domain by using multi-walled carbon nanotubes (MWCNT) as movable part instead of micrometric membranes into reconfigurable passive circuits for microwave applications. For such a study, horizontal configuration of the NEMS varactors has been chosen and is commented. The technology is established to fulfill several constraints, technological and microwave ones. As far as technological requirements are concerned, specific attentions and tests have been carried out to satisfy: • Possible and later industrialization. No e-beam technique has been selected for RF NEMS varactor elaboration. Lateral MWCNT growth performed on a Ni catalyst layer, sandwiched between two SiO2 layers, showed feasibility of suspended MWCNT beam. • High thermal budget, induced by the MWCNT growth by CVD (Chemical Vapor Deposition), at least to 600°C. All the dielectric and metallic layers, required to interlink the nano world with the micrometric measurements one, have been studied accordingly. Consequently, the order of the technological steps has been identified. About microwave and actuation specifications (targeted close to 25V), the minimization of losses and actuation voltage implies large layer's thicknesses compared to the CNT diameter. Several specific technological issues are presented in this paper, taking care of both technological and microwave compatibility to go toward RF NEMS varactor's elaboration.
- [Show abstract] [Hide abstract] ABSTRACT: For applications such as computers, cellular telephones and Microsystems, it is essential to reduce the size and the weight of DC-DC converters. To miniaturize passive components, micromachining techniques provide solutions based on low-temperature process compatible with active part of the converter. This paper deals with the integration on silicon of "spiral-type" inductor topology. Electroplating techniques are used to achieve the copper conductor and the CoNiFe laminated magnetic core and several investigations on the electroplating bath's parameters have been realized in order to obtain the adequate magnetic properties. Finally, a 1muH micro-inductor prototype has been characterized.
Conference Paper: RF Nanoelectromechanical switch employing nanowires[Show abstract] [Hide abstract] ABSTRACT: In this work, we present the results of our investigations of an RF nanoswitch device based on nanowires array. The nanowires are used to make a DC contact between the signal line of a CPW line and its ground. Silicon is used as a substrate. The switch is formed by the nanowire and the pillar.The design of a RF NEMS based on vertical metallic nanowires array shows a good performance up to 27 GHz.
Conference Paper: Si3N4 thin films proprerties for RF-MEMS reliability investigation[Show abstract] [Hide abstract] ABSTRACT: This paper investigate the dielectric charging mechanisms in Si<sub>3</sub>N<sub>4</sub> thin films versus different elaboration conditions and different characterization method. Transient currents measurements in PECVD SiNx were performed versus electrical field, temperature and time. These results suggest a dominant conduction mechanism and allow to predict the amount of charge injected into the dielectric and the charge/discharging kinetics processes. The deposition parameters effects, evaluated by FTIR, in order to identify the chemical bond in the dielectric, can explain the charging behavior. Injection and detection of electrical charges by atomic force microscopy at the nanometer scale can be used for studying the dynamic and the propagation of the deposited charges. This observation coupled to transient currents measurements, and FTIR,-can give rules for the best dielectric choice for this particular application.
- [Show abstract] [Hide abstract] ABSTRACT: Liquid crystalline thin films elastomers that are able to bind pesticides have been developed. The synthesis involves grafting mesogen and crosslinkable groups on a polysiloxane chain in the presence of a template molecule. The molecular imprinted material is obtained after thin film deposition, UV crosslinking and washing. Experiments of readsorption of pesticide are presented. Development of a multisensor platform based on thermal and capacitive sensors is described and tests of deposition of the polymer film are presented.
- [Show abstract] [Hide abstract] ABSTRACT: We present in this paper trends and technologies for the integration of inductors for DC-DC microconverters. In particular, we present the fabrication steps of different structures as a function of the application: planar inductors for low power consumption, and 3D magnetic inductors for higher power. These devices are achieved using low temperature fabrication processes based in photolithography or and electroplating techniques.
- [Show abstract] [Hide abstract] ABSTRACT: This paper describes the fabrication steps of a spiral-type inductor designed for power electronics conversion. Realized on silicon wafer and using photolithography and electroplating techniques, this microinductor is composed of a copper spiral conductor sandwiched between two iron-nickel laminated magnetic layers. Furthermore, specific devices have been realized in order to characterize the magnetic material
- [Show abstract] [Hide abstract] ABSTRACT: 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.
Conference Paper: New design for magnetic storage elements of micro power supplies[Show abstract] [Hide abstract] ABSTRACT: In the fast growth context of micro-electromechanical systems (MEMS) applications, an important improvement of power supplies "power-to-weight" ratio can be obtained through the integration of magnetic storage elements with their associated electronic environment. These components are usually used to transfer and store high energy densities with high magnetic flux. But up until now, integrated devices with these inductive elements were mainly limited by low inductance and current values. To make optimised new designs and achieve realisation of such inductive elements, we propose a new complete methodology, illustrated through a micro-machined square planar inductor. Indeed, after defining specifications (power, inductance value, frequency, geometrical dimensions), a mathematical method is used to define a first geometrical parameters set. To achieve it, several simulations are conducted with CAD tools dedicated to MEMS technology. Our method is based on a new specific last nano-imprint technology we have developed in our laboratory and adapted, in parallel, to our application
- [Show abstract] [Hide abstract] ABSTRACT: Compactness, complexity of the interconnections and specific packaging, which are characteristics of Microsystems (MEMS), rule out the use of statistical procedure to assess reliability in space applications. Predictable reliability is the method recommended in this paper that uses a similar approach as CALCE already did for hybrid and microelectronic circuits. This method based on a failure mechanism approach is recalled at first and an example to illustrate this procedure based on the evolution of material crystal properties under radiation is presented.
French National Centre for Scientific Research
Lutetia Parisorum, Île-de-France, France
- Laboratoire d'analyse et d'architecture des systèmes (LAAS)
Johns Hopkins MedicineBaltimore, Maryland, United States
University of ToulouseTolosa de Llenguadoc, Midi-Pyrénées, France