Laurent A Francis
Laurent A. Francis was born in Ottignies-Louvain-la-Neuve, Belgium, in 1978. He received the M.Eng. degree in materials science with a minor in electrical engineering (summa cum laude) and the PhD degree in applied sciences from the Université catholique de Louvain (UCL), Louvain-la-Neuve, Belgium, in 2001 and 2006, respectively. Since September 2007, he holds the Microsystems Chair position at UCL as associate professor and is leading member of the research group Sensors, Microsystems and Actuators Laboratory of Louvain (SMALL). His PhD thesis was related to acoustic-wave based microsystems for biosensing applications at IMEC (Interuniversity MicroElectronics Center) in Leuven. Between 2000 and 2007 he was with IMEC as researcher, successively in the Biosensors and RF-MEMS groups. In 2011, he was visiting professor at the Université de Sherbrooke, Canada. His scientific interests are related to co-integrated CMOS MEMS and NEMS sensors, harsh environment ultra-low power sensors, biomedical sensors, atomic layer deposition, bio-inspired approaches and device packaging. He is regular member of IEEE (UFFC, MTT and EMBS) and a board member of the Belgian National Committee Biomedical Engineering. He is member of the editorial advisory board of the “Sensors and Transducers Journal” and of the editorial board of the “Journal of Sensors” (Hindawi Publ. Corp.) He has authored or co-authored more than 70 scientific publications in international journals, conferences and book chapters, and holds one patent.
Phone: +32 10 47 35 33
Address: Maxwell building, Place du Levant 3,
B-1348 Louvain-la-Neuve
Belgium
Phone: +32 10 47 35 33
Address: Maxwell building, Place du Levant 3,
B-1348 Louvain-la-Neuve
Belgium
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Papers by Laurent A Francis
In this work, the design, characterization, and integration of sensing systems are assessed with a generic approach in order to obtain portable, simple, and power efficient solutions. A methodology of the instrumentation system design is proposed in order to push the maturity of the systems technology from the fundamental research to a pre-industrial stage. The proposed interfacing principle is based on the insertion of the sensor into triangular voltage oscillating circuits. The data captured by the sensor deforms the analog output of the oscillator and is extracted by mathematical methods. The methodology is applied for two applicative contexts: 1) liquid sensing, and 2) the detection of variable magnetic fields.
The first system for liquid sensing consists in an interdigitated electrodes (IDE), the sensing device is investigated and modeled using finite elements tools. The interfacing approach consists in stimulating the device with a square current wave; this results in a triangular output voltage with a shape that embeds the liquid properties, i.e., both conductivity and permittivity.
The second system is a detector of magnetic field variations, e.g., for abrupt variations of power line currents. The sensing element is a square planar inductor modeled similarly to the IDE. Being also based on a triangular voltage oscillating system, the interfacing method we built consists in varying the triangular signal frequency for each detected magnetic perturbation. Output characteristics are consequently defined to quantify the amount of magnetic perturbations captured by the inductor. The system has been successfully tested for the detection of arc faults on high-powered current lines. We demonstrate that integrating the interface in current CMOS technologies can lead to data acquisition in the µW regime.
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In this work, the design, characterization, and integration of sensing systems are assessed with a generic approach in order to obtain portable, simple, and power efficient solutions. A methodology of the instrumentation system design is proposed in order to push the maturity of the systems technology from the fundamental research to a pre-industrial stage. The proposed interfacing principle is based on the insertion of the sensor into triangular voltage oscillating circuits. The data captured by the sensor deforms the analog output of the oscillator and is extracted by mathematical methods. The methodology is applied for two applicative contexts: 1) liquid sensing, and 2) the detection of variable magnetic fields.
The first system for liquid sensing consists in an interdigitated electrodes (IDE), the sensing device is investigated and modeled using finite elements tools. The interfacing approach consists in stimulating the device with a square current wave; this results in a triangular output voltage with a shape that embeds the liquid properties, i.e., both conductivity and permittivity.
The second system is a detector of magnetic field variations, e.g., for abrupt variations of power line currents. The sensing element is a square planar inductor modeled similarly to the IDE. Being also based on a triangular voltage oscillating system, the interfacing method we built consists in varying the triangular signal frequency for each detected magnetic perturbation. Output characteristics are consequently defined to quantify the amount of magnetic perturbations captured by the inductor. The system has been successfully tested for the detection of arc faults on high-powered current lines. We demonstrate that integrating the interface in current CMOS technologies can lead to data acquisition in the µW regime.
and on the capacitive and piezoresistive transduction mechanisms of MEMS is investigated. MEMS technologies could revolutionize avionics, satellite and space applications provided that the stress conditions which can compromise the reliability of microsystems in these environments are well understood. Initial tests with MEMS revealed a vulnerability of some types of devices to radiation induced dielectric charging, a physical mechanism which also affects microelectronics, however integration of novel functional materials in microfabrication and the current trend to substitute SiO2 with high-k dielectrics in ICs pose new questions regarding
reliability in radiation environments. The performance of MEMS devices with moving parts could also degrade due to radiation induced changes in the mechanical properties of the materials. It is thus necessary to investigate the effects of radiation on the properties of thin films used in microfabrication and here we report on tests with γ, high energy protons and fast neutrons radiation. Prototype SOI based MEMS magnetometers which were developed in UCL are also used as test vehicles to investigate radiation effects on the reliability of magnetically actuated and capacitively coupled MEMS.
In this talk, we will see how borrowing photonic crystals from Nature with the support of micro and nanotechnologies can lead to new synthetic photonic structures that would improve the performances of solar cells, light-emitting diodes and nanosensors. More specifically, we will show 1) the replication of butterfly wings directly on the surface of silicon to improve the light absorption of silicon solar cells, 2) a new concept inspired by firefly to enhance the light extraction of GaN-based light-emitting diodes, and 3) the Bragg reflectors cavities of butterflies and beetles to develop new types of microsensors.
The different cases will highlight key technologies such as atomic layer deposition, nano-imprint, direct laser writing or colloids to fabricate bio-inspired photonic structures, all along with an in-depth understanding of the optical behavior of natural structures helped by the direct observation of samples, their modeling and simulation.
Recently, it was reported that Si solar cells with the Al2O3 coating show a high-efficiency [4]. We investigate the optical and electrical properties of the low-temperature ALD Al2O3 layer. According to the flat-band voltage ΔV extracted from the high frequency C-V curve, we also estimate the negative charge density in the Al2O3 layer to be 3 x 1012 /cm2, which will provide an effective field-effect passivation for reducing the surface recombination of the minority carriers. These results demonstrates large potential on applying the replicated butterfly wing patterns on Si wafer with the Al2O3 coating for photovoltaic applications with high antireflection and lower combination properties.
References:
[1] J. Huang et al., Nano Letters, 6, 2325 (2006).
[2] D.P. Gaillot et al., Physical Review E 78, 031922 (2008).
[3] S. Eon et al., Nano Letters, 10 1012 (2010).
[4] B. Hoex et al., J. Appl. Phys. 104, 113703 (2008).
In order to help you to get an answer to this question, the tutorial will be divided in three main parts divided between operation principles, fabrication techniques and application examples.
The first part will cover the operation principles that have the highest interest for biomedical applications. Going small means basically changing the point of view on physical and chemical behaviors: surface related effects will largely affect body and fluid motions, molecules sensing, thermal flows, … when compared to body related effects to which we, as human beings, are used. Going small is advantageous for faster detection, with minute amount of materials needed, or in order to be less invasive.
The second part will address the basics of fabrication techniques that allow us to obtain micro-engineered biomedical devices. Also, interfacing miniaturized devices with the outer world is often the most difficult part, where the electrical and fluidic continuity between macro and micro worlds has to be considered with the right attention. This last point is often merged with the device packaging; we will see that this point is far from obvious while it critically contributes to a successful real-life application of the microsystem.
The third and last part of the tutorial will address scientific challenges and opportunities offered by a comprehensive approach of microsystems as done in research performed at the Université catholique de Louvain. Examples will be presented like a wireless breath sensor used for the re-education of elderly people, or like devices for bacteria, DNA or protein detection. All in one, they will trend to indicate that small devices are adequate for biomedical applications.
- a Booklet of Abstracts with the full day program, the keynote speaker abstracts and bio's, and the list of posters
- a PDF of the following keynotes
o "Inaugural session of the Microsystems Chair " by Laurent Francis, Université catholique de Louvain
o "From Microelectronics to Microsystems " by Jean-Pierre Raskin, Université catholique de Louvain
o "RF-MEMS: an enabling technology for reconfigurable radio front-ends " by Harrie Tilmans, IMEC
o "Surface Acoustic Devices for Wireless Passive Sensors " by Sylvain Ballandras and Jean-Michel Friedt, CNRS FEMTO-ST
o "RF MEMS at EADS: Concept, Designs, and Applications " by Bernhard Schoenlinner, EADS Innovation Works
o "MEMS Industry and Market Overview " by Jérémie Bouchaud, WTC Wicht Technologie Consulting
Featuring contributions by academic and industrial researchers from around the world, this book:
Examines organic and flexible electronics, from polymer solar cell to flexible interconnects for the co-integration of micro-electromechanical systems (MEMS) with complementary metal oxide semiconductors (CMOS)
Discusses imaging and display technologies, including MEMS technology in reflective displays, the fabrication of thin-film transistors on glass substrates, and new techniques to display and quickly transmit high-quality images
Explores sensor technologies for sensing electrical currents and temperature, monitoring structural health and critical industrial processes, and more
Covers biomedical microsystems, including biosensors, point-of-care devices, neural stimulation and recording, and ultra-low-power biomedical systems
Written for researchers, engineers, and graduate students in electrical and biomedical engineering, this book reviews groundbreaking technology, trends, and applications in microelectronics. Its coverage of the latest research serves as a source of inspiration for anyone interested in further developing microsystems technologies and creating new applications.