Elisabeth Dufour-Gergam

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (75)76.45 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Reversible packaging is very desirable for microfluidic chips: it allows changing the chip upper cap when it is damaged, cleaning and reusing the chip bottom substrate. This latter case becomes even more attractive when integrated components are present on the substrate and have required a complex and expensive microfabrication process. The feasibility of poly(dimethylsiloxane) (PDMS)/PDMS and PDMS/glass reversible bonding is demonstrated using the stamping technique. Dimethyl-methylphenylmethoxy siloxane (DMPMS), a type of silicone conformal coating, is used as an adhesive layer between the PDMS channel and the substrate (PDMS or glass). This technique is easy to perform as it only needs spin-coating and thermal curing steps. The bond strength is suitable for high working flow rate/pressure of liquid in the channel (up to 500 mu l/min and 200 kPa). The cycle 'pealing/bonding' of the cap can be repeated up to five times. In addition, an MTT cell proliferation assay has been performed and suggests the non-cytotoxicity of DMPMS. Thus, the DMPMS-stamping bonding technique opens new perspectives for PDMS biochips where plasma treatment is not possible such as functionalised surfaces.
    Micro & Nano Letters 05/2015; DOI:10.1049/mnl.2014.0581 · 0.80 Impact Factor
  • T.H.N. Dinh, E. Martincic, E. Dufour-Gergam, P.-Y. Joubert
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    ABSTRACT: Kapton-based flexible pressure sensor arrays are fabricated using a new technology of film transfer. The sensors are dedicated to the non-invasive measurement of pressure/force in robotic, sport and medical applications. The sensors are of a capacitive type, and composed of two millimetric copper electrodes, separated by a polydimethylsiloxane (PDMS) deformable dielectric layer. On the flexible arrays, a very small curvature radius is possible without any damage to the sensors. The realized sensors are characterized in terms of fabrication quality. The inhomogeneity of the load free capacitances obtained in the same array is ±7 %. The fabrication process, which requires 14 fabrication steps, is accurate and reproducible: a 100 % transfer yield was obtained for the fabrication of 5 wafers gathering 4 sensor arrays each (215 elementary sensors). In the preliminary electro-mechanical characterization, a sensor (with a PDMS dielectric layer of 660 μm thickness and a free load capacitance of 480 fF) undergoes a capacitance change of 17 % under a 300 kPa normal stress.
    Microsystem Technologies 01/2015; 21(5):1-7. DOI:10.1007/s00542-015-2540-5 · 0.95 Impact Factor
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    ABSTRACT: Reversible bonding that allows repeating assembly and disassembly of microfluidic devices is very useful for a number of applications such as surface functionalization, complex cell patterning, and other biological analysis. However, reversible microfluidic devices fabricated with the current standard procedures can only be used for low-pressure applications. In this paper, we describe and characterize a reliable, flexible, and reversible bonding technique of PDMS-PDMS (Poly-dimethyl siloxane) using an oxygen plasma treatment. Effects of control parameters, such as the thickness of the PDMS layer, the duration and power of the plasma treatment, the duration and temperature of the thermal treatment on the quality of the obtained devices are investigated. An optimal set of control parameters enabling the obtained devices to work at high flow rates and pressures (500 µL/min and 148 kPa) has been determined. Furthermore, the disassembly/assembly process of the device can be repeated up to four times.
    Microfluidics and Nanofluidics 01/2015; DOI:10.1007/s10404-015-1599-8 · 2.67 Impact Factor
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    ABSTRACT: Research activities developed in the “Micro-devices for bio-medical applications” team at IEF focus on the development of technological processes for the design and realization of micro-devices dedicated to biological and medical applications. Devices operating at molecular or cellular scales, up to tissue or organic scales are considered in our developments. Our work emphasizes the development of non-invasive and/or biocompatible devices, with wearable or in-vivo device implementations in view. The presentation is focused on flexible micro-devices dedicated to non-invasive medical applications.
    2nd Advanced Technology Workshop on Microelectronics, Systems and Packaging for Medical Applications, Lyon, France; 12/2014
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    ABSTRACT: Cells submitted to an electric field gradient experience dielectrophoresis. Such a force is useful for pairing cells prior to electrofusion. The latter event is induced by the application of electric field pulses leading to membrane fusion while cells are in physical contact. Nevertheless, the efficiency of dielectrophoretic pairing and electrofusion of cells are highly dependent on medium properties (osmolarity and conductivity). In this paper, we examine the effect of medium osmolarity on volume, viability and electrical properties of cells. Then we characterize in real time the impact of electropermeabilization of cells on their dielectrophoretic response. To do so, a microfluidic device, inducing particular field topologies is used. These real time observations are correlated to numerical analysis of the Clausius-Mossotti factor. Taking into account the identified changes, an electrofusion protocol adequate to the optimal medium (100 mOsm, 0.03 S/m) is defined. Up to 75 % simultaneous binuclear rapid electrofusions were achieved and monitored with average membrane fusion duration lower than 12 s.
    Bioelectrochemistry 12/2014; DOI:10.1016/j.bioelechem.2014.05.004 · 3.87 Impact Factor
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    ABSTRACT: Wearable pressure sensors arrays are required for various monitoring purposes in medicine. To meet with the wanted specifications, capacitive sensors arrays realized on highly flexible substrates have been proven to be good candidates to let non-invasive as well as accurate stress measurements to be carried out. Since single-axis pressure measurements may be found incomplete in some applications, capacitive arrays featuring 3-axes pressure sensing capabilities are considered in this study. A sensor array prototype featuring 25 element 3-axes micro-sensors are designed. They are realized on a flexible substrate (Kapton) using PDMS as a deformable dielectric material, by means of an original transfer of film technique. The principle of operation of such sensors is based on the capacitance change of capacitive sensors with the deformation of the dielectric layer separating the sensor electrodes, under an applied stress. Finite element computations are carried to foresee and optimize the sensors sensitivity to stress. Electromechanical tests are carried out on the realized sensors for validation purposes.
    IEEE SENSORS 2014; 11/2014
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    ABSTRACT: In this paper, we describe and characterize a novel method, based on silanization, for strong bonding of SU8 microchannels to poly(dimethyl)siloxane (PDMS) flexible covers. First, the SU8 surface treatment process (silanization) is characterized through atomic force microscopy and contact angle measurements. The aging study proves grafting stability during more than two days. Silanized SU8 patterns and PDMS cover are finally bonded to seal the microchannel network. Such assembled microdevices can be used without leakage at flow rates above 2.4 mL/min, corresponding to 1.2 MPa if the PDMS deformation is neglected. The bonding tensile pressure exceeds 1.5 MPa, proving the packaging strength. Furthermore, SU8-PDMS composite devices display stable bonding after several weeks of storage. This rapid low cost and low temperature bonding technique is finally successfully employed to fabricate a fully packaged biochip for electric and fluidic handling of biological cells. [2014-0116]
    Journal of Microelectromechanical Systems 10/2014; 23(5):1015-1024. DOI:10.1109/JMEMS.2014.2331454 · 1.92 Impact Factor
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    ABSTRACT: In this paper, the design, the fabrication and the electromechanical characterization of polymer-based flexible pressure sensor are presented. This kind of sensors is developed for the non-invasive monitoring of pressure/force distributions that is required in many medical applications such as the monitoring of plantar pressures or chronic venous disorder treatments. The sensors considered in this paper are of a capacitive type. They are composed of two millimetric copper electrodes, separated by polydimethylsiloxane (PDMS) dielectric layers and deposited on a Kapton substrate. A study of the deformation of PDMS thin films under normal stress is carried out by finite element computations as well as experiments. This study points out a sensor design optimization parameter, the form ratio of the indented PDMS layer, which is used to design and fabricate capacitive micro-sensors samples. Preliminary electromechanical characterizations of realized sensor samples validate the approach. Under a 10 N normal stress, the sensitivity of 9 square mm sensors varies from 3% up to 17% in capacitive change, according to the chosen form ratio of the used PDMS layer.
    2014 IEEE International Symposium on Medical Measurements and Applications (MeMeA), Lisbon, Portugal; 06/2014
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    ABSTRACT: Kapton-based flexible pressure sensor arrays are fabricated using a new technology of film transfer. The sensors are dedicated to the non-invasive measurement of pressure/force in robotic, sport and medical applications. The sensors are of a capacitive type, and composed of two millimetric copper electrodes, separated by a polydimethylsiloxane (PDMS) deformable dielectric layer. On the flexible arrays, a very small curvature radius is possible without any damage to the sensors. The inhomogeneity of the capacitances in array is quite low (deviation of ±7% compared to the average value). The process is accurate and reproducible (transfer yield of 100%). The electrical characterization is also presented. In the preliminary electro-mechanical characterization, a sensor (with a PDMS dielectric layer of 660 μm thickness and a free load capacitance of 480 fF) undergoes a capacitance change of 17% under a 300 kPa normal stress.
    Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS (DTIP), 2014, Cannes, France; 04/2014
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    ABSTRACT: The aim of this work is to develop a sensitive and specific immune-sensing platform dedicated to the detection of potential biomarkers of Alzheimer disease (AD) in biological fluids. Accordingly, a controlled and adaptive surface functionalization of a silicon wafer with 7-octenyltrichlorosilane has been performed. The surface has extensively been characterized by AFM (morphology) and XPS (chemical composition) and contact angle measurements. The wettability of the grafted chemical groups demonstrated the gradual trend from hydrophilic to hydrophobic surface during functionalization. XPS evidenced the presence of silanes on the surface after silanization, and even carboxylic groups as products from the oxidation step of the functionalization process. The characterization results permitted us to define an optimal protocol to reach a high-quality grafting yield. The issue of the quality of controlled chemical preparation on bio-receiving surfaces was also investigated by the recognition of one Alzheimer disease (AD) biomarker, the Amyloïd peptide Aβ 1-42. We have therefore evaluated the biological activity of the grafted anti Aβ antibodies onto this silanized surface by fluorescent microscopy. In conclusion, we have shown, both qualitatively and quantitatively, the uniformity of the optimized functionalization on slightly oxidized silicon surfaces, providing reliable and chemically stable procedure to determine specific biomarkers of Alzheimer disease. This work opens the route to the integration of controlled immune-sensing applications on lab-on-chip systems.
    Langmuir 03/2014; 30(20). DOI:10.1021/la500695y · 4.38 Impact Factor
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    ABSTRACT: Cell fusion consists of inducing the formation of a hybridoma cell containing the genetic properties of the progenitor cells. Such an operation is usually performed chemically or electrically. The latter method, named electrofusion, is considered as having a strong potential, due to its efficiency and non-toxicity, but deserves further investigations prior to being applicable for key applications like antibody production and cancer immunotherapy. Indeed, to envision such applications, a high amount of hybrid cells is needed. In this context, we present in this paper a device for massive cell pairing and electrofusion, using a microarray of non-connected conductive pads. The electrofusion chamber––or channel––exposes cells to an inhomogeneous electric field, caused by the pads array, enabling the trapping and pairing of cells with dielectrophoresis (DEP) forces prior to electrofusion. Compared to a mechanical trapping, such electric trapping is fully reversible (on/off handling). The DEP force is contactless and thus eases the release of the produced hybridoma. Moreover, the absence of wire connections on the pads permits the high density trapping and electrofusion of cells. In this paper, the electric field mapping, the effect of metallic pads thickness, and the transmembrane potential of cells are studied based on a numerical model to optimize the device. Electric calculations and experiments were conducted to evaluate the trapping force. The structure was finally validated for cell pairing and electrofusion of arrays of cells. We believe that our approach of fully electric trapping with a simple structure is a promising method for massive production of electrofused hybridoma.
    07/2013; 7:044101. DOI:10.1063/1.4813062
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    ABSTRACT: Electrodeposition of SmCo in aqueous solution has been studied using a Hull cell. Different concentrations of cobalt ion in the electrolyte, addition of supporting electrolyte and different deposition time have been tested. High samarium contents and thicknesses have been obtained: up to 50 % of Sm in the deposit and several microns. The oxygen contamination is linked to the samarium content and two elaboration parameters have been found for limiting this contamination: addition of supporting electrolyte and long deposition time.
    ECS Transactions 04/2013; 45(14):15-23. DOI:10.1149/04514.0015ecst
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    ABSTRACT: In this paper, we investigate the different parameters that affect the distribution of the transmembrane potential of cells brought into contact before electrofusion in a miniaturized fluidic device. In particular, we discuss the deviation of the effective transmembrane voltage compared to the one predicted by Schwan’s law. The application of electric field pulses to biological cells induces a transmembrane potential which leads to cell permeabilization. Electrofusion occurs when several cells are brought into contact while they are electropermeabilized. Nevertheless, we show that in this case, the mutual presence of cells interferes on Schwan’s equation. Consequently, the transmembrane voltage at the cell contacting point is drastically reduced, which is not favorable for an electrofusion in smooth conditions, as the applied voltage needs to be increased to compensate this phenomenon. We show that the introduction of polymer obstacles reverses this trend, as the high electric field region is focused on the fusion zone. To confirm the theory we developed, quantitative biological experiments are presented in which murine melanoma cells were paired and fused in both conditions (with and without obstacles).
    The European Physical Journal Applied Physics 04/2013; 62(1):11202. DOI:10.1051/epjap/2013120392 · 0.79 Impact Factor
  • BiodevicesBiodevices; 01/2013
  • T.H.N. Dinh, P.-Y. Joubert, E. Martincic, E. Dufour-Gergam
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    ABSTRACT: This paper presents an efficient and reproducible fabrication process of flexible-substrate-based pressure sensor arrays, using a technology of film transfer which has been recently developed in our laboratory [1]. The sensors are composed of two millimetric copper electrodes, separated by a polydimethylsiloxane (PDMS) dielectric layer, the operation of which is based on a capacitance change induced by an applied force. Sensor arrays were fabricated on two types of substrate: a rigid substrate (glass) used for the validation of the fabrication process, and a flexible substrate (Kapton) used to realize the wanted flexible sensors. Regarding the flexible arrays, a very small curvature radius is possible without any damage to the sensors. Six three-by-three sensor arrays were fabricated. They feature capacitances ranging from 3.45 pF to 14.40 pF, according to their dimensions. The discrepancy between the capacitances within each array is quite low (standard deviation is less than 7 % of the mean value). The sensitivity of the considered on-glass samples is around 80 pF/mN under 2N loading conditions.
    IEEE Sensors 2013, Baltimore, MD; 01/2013
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    ABSTRACT: Combined with high-field MRI scanners, small implanted coils allow for high resolution imaging with locally improved SNR, as compared to external coils. Small flexible implantable coils dedicated to in vivo MRI of the rat brain at 7T were developed. Based on the Multi-turn Transmission Line Resonator design, they were fabricated with a Teflon substrate using copper micromolding process and a specific metal-polymer adhesion treatment. The implanted coils were made biocompatible by PolyDimethylSiloxane (PDMS) encapsulation. The use of low loss tangent material achieves low dielectric losses within the substrate and the use of the PDMS layer reduces the parasitic coupling with the surrounding media. An implanted coil was implemented in a 7T MRI system using inductive coupling and a dedicated external pick-up coil for signal transmission. In vivo images of the rat brain acquired with in plane resolution of (150μm)(2) thanks to the implanted coil revealed high SNR near the coil, allowing for the visualization of fine cerebral structures.
    Journal of Magnetic Resonance 09/2012; 224:61-70. DOI:10.1016/j.jmr.2012.09.003 · 2.32 Impact Factor
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    ABSTRACT: In this paper, we present a technological process giving access to fully embedded copper tracks into PDMS stacked layers, with adapted processes for single side metallization, double side or heterogeneous flexible layers. Examples of mi-crocoils, double side MRI micro-antennae and heterogeneous capacitive pressure sensor using a hybrid process are presented as demonstration devices. Patterns examples of sizes from 5 µm up to 4 mm are shown. The transfer process yield is higher than 95% in all cases, but the adhesion mechanisms seem to be a function of the patterns geometry together with physical and chemical adhesion mechanisms.
    23rd Micromechanics and Microsystems Europe Workshop, Ilmenau, Germany; 09/2012
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    ABSTRACT: We propose a concept of very specific immune-sensing platform dedicated to the quantification of biomarkers of Alzheimer disease (AD) in biological fluids. High sensitivity is required for the earliness of AD diagnostic, mainly based on clinical evaluation at present time. Accordingly, a controlled and adaptative surface functionalization of a silicon wafer with carboxylated alkyltrichlorosilane has been developed. The surface has extensively been characterized by AFM and X-ray Photoemissive Spectroscopy. The surface modification has been chemically assessed by XPS at each functionalization step. The survey spectra of silicon surface, after, 1, 3, 6 and 24h of silanisation, highlight a significant enhancement of the functionalization efficiency upon time. The oxidation reaction has also been investigated by XPS and showed components related to the carboxylic group. AFM measurements pointed out a morphological modification consistent with a homogenous development of the carboxylic group and an almost protein monolayer on the surface. Moreover, we evaluated the biological activity of the grafted antibodies involved in (AD) biomarker detection onto this silanized surface by fluorescent microscopy. A sandwich immunoassay dedicated to the sensitive detection of one biomarker of Alzheimer disease (AD), the amyloid peptide 1-42 (Aβ 1-42), was carried out. The results demonstrated that the controlled silanized surface provides a novel and viable way to detect biomarkers with high specificity and open the route to an original development of immune-sensing applications on such surfaces.
    Biosensors & Bioelectronics 08/2012; 40(1). DOI:10.1016/j.bios.2012.07.072 · 6.45 Impact Factor
  • M Deterre, E Lefeuvre, E Dufour-Gergam
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    ABSTRACT: This paper presents an energy harvesting technique to power autonomous systems and more particularly active implantable medical devices. We employ a piezoelectric diaphragm placed in a fluidic environment such as blood subjected to very low frequency (2 Hz) pressure variations that is deflected in a quasi-static manner and transduces mechanical energy into electrical energy. In order to maximize energy generation and to get the most out of a given piezoelectric device, we propose to apply an optimized method to extract the piezoelectrically generated charge through the application of a controlled voltage. We believe that this method could be one of the improvement levers to achieve self-powered miniaturized implants. An analytical model is presented and shows that within its validity domain, the extracted energy is proportional to the desired applied voltage. Taking power electronics losses into account can yield a theoretical increase in the extracted energy of several thousand per cent. Experimental measurements in a pressure chamber have been carried out whose results corroborate the proposed model. For the tested setup, the application of a 10 V peak amplitude square-wave voltage increased the extracted energy by a factor of nine compared to a classical rectifier-based energy harvesting method.
    Smart Materials and Structures 08/2012; 21(8). DOI:10.1088/0964-1726/21/8/085004 · 2.45 Impact Factor
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    ABSTRACT: Despite the large use of this material in the microsystem field, fabrication of metallic patterns on polydimethylsiloxane (PDMS) still remains a challenge. In this Letter, we present a new process based on the transfer principle and report its application to MRI microcoils. These double-side structures are well aligned and the transfer yield is higher than 90%. The limit of the working range for these flexible coils is a bending radius of 2%mm, similar to the radius of the coil. The developed process opens a wide range of further applications for flexible devices.
    Micro & Nano Letters 06/2012; 7(6):519-522. DOI:10.1049/mnl.2012.0271 · 0.80 Impact Factor

Publication Stats

269 Citations
76.45 Total Impact Points

Institutions

  • 2007–2014
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 1998–2014
    • Université Paris-Sud 11
      • Institut d'Electronique Fondamentale
      Orsay, Île-de-France, France
  • 2002–2009
    • Institute of Fundamental Electronics
      Orsay, Île-de-France, France