Local probing of the field emission stability of vertically aligned multiwalled carbon nanotubes

Metallic cantilever in high vacuum atomic force microscope has been used as anode for field emission experiments from densely packed vertically aligned multi-walled carbon nanotubes. The high spatial resolution provided by the scanning probe technique allowed precise setting of the tip-sample distance in the submicron region. The dimension of the probe (curvature radius below 50nm) allowed to measure current contribution from sample areas smaller than 1um^2. The study of long-term stability evidenced that on these small areas the field emission current remains stable (within 10% fluctuations) several hours (at least up to 72 hours) at current intensities between 10-5A and 10-8A. Improvement of the current stability has been observed after performing long-time Joule heating conditioning to completely remove possible adsorbates on the nanotubes.Comment: 15 pages, 7 figure

Micro EDM Milling with Low Energy Discharges and Thin Microtool

International audienceThe aim of this paper is to report on micro EDM milling of stainless steel with ultrathin and high aspect ratio microtools and explore possibilities for machining with small discharges using a ballast resistor. Machining of channels is demonstrated with a 9 µm tungsten microtool with 29 nJ/discharge without damaging the tool. Depending on the value of the ballast resistor Rb, the channel width is about 31-36 µm with aspect ratio of 1.4-1.8. The most significant result is that the relative tool wear ratio is below 0.01% when Rb is greater than 100 Ω. It allows machining at 50 V operating voltage with 1 nF working capacitance without using the stray capacitance of the machine

Omnidirectional inductive wireless charging of a 3D receiver cube inside a box

International audienceOmnidirectional inductive wireless charging of a 6×6×6 cm3 3D receiver cube with 6 planar coils inside a 47×47×47 cm 3 box with 4 planar emitting coils is studied. The power delivered to the cube in the central position of the box is in the 1 W-2.4 W range with 6-7% transfer efficiency. In this position , the power is insensitive to the pitch angular orientation. When moving the 3D receiver cube toward the corners of the box, there is no sudden drop of transmitted power. However, the delivered power near the corners increases or decreases in an acceptable range depending on the orientations of the magnetic field of the emitters. Perspectives of this work, when replacing the manufacturing of coils based on PCBs technology by 3D Molded Interconnect Device technology, are briefly discussed

Study of the resistance variation of IME circuit conductor tracks after thermoforming during manufacturing

International audienceAbstract:Over the past 15 years, Printed Electronics (PE) has established itself as a technological solution for the low-cost production of electronic circuits on many types of non-conventional substrate (polymer, wood, paper...) in Electronics. At the same time, 3D Plastronics has made it possible to produce electronic circuits on the curved surface of polymer parts. The convergence of PE and 3D Plastronics has given rise to the IME (In-Mold Electronic) technique. First, an electronic circuit is screen-printed onto a polymer sheet using conductive ink. The electronic components are then transferred and connected to the circuit with conductive glue to create a functional 2D circuit on the polymer. To be transferred on the 3D surface of a polymer part, the circuit is then thermoformed and overmolded.However, the thermoforming step results in the deformation of the circuit's conductor tracks, creating high stresses leading to deformation until the conductor tracks break or the components pull out.As a result, IME products on the market today, feature low curvature to minimize conductor deformation and stress on transferred components.In order to assess the impact of thermoforming on conductor tracks, we undertook a study of the deformation of conductor tracks and the evolution of their electrical resistance as a function of stretch and temperature using a tensile stress machine. We have also simulated substrate thermoforming using a coupled thermo mechanical model (Abaqus/Explicit solver) Coupled with the evolution of the resistance of the conductor tracks during stretching, these simulations should make it possible to predict the electrical characteristics of the thermoformed circuit, and ultimately to establish design rules for IME circuits. Measurements and simulations results will be presented and discussed.Moreover, design strategy of the electronic circuit will be discussed to avoid the conductor tracks break and minimize their resistance variation. Lastly, different promising strategies to anticipate and correct the pattern deformation will be discussed, as well potential applications of this work in different fields (antennas, high density IME, etc.)

The Potential of 3D-MID Technology for Omnidirectional Inductive Wireless Power Transfer

International audienceOmnidirectional inductive wireless charging system of a mobile is studied. Instead of using conventional planar coils printed on circuit boards, 3D Molded Interconnect Device (3D-MID) coils are used. The receiver is a single piece that has 3 elliptic inductors pointing in 3 different directions of the space. A half meter cubic box with 4 planar emitting inductors on 4 sides is used to transmit power at 6.78 MHz to the receiver inside the cube, regardless to the position and orientation of the receiver. Measurement results show that the 3D-MD receiver can get a power of 1.4 W at 7.9% efficiency on most of the positions inside the box. When the receiver is at the central position and also in the corners of the box, there is little variation of the transferred power when the receiver turns 360°, which means that it is almost insensitive to angular misalignment. However, when the receiver moves from the center towards the corners, there is a drop or an increase of power, which means that there is a lack of uniformity of the power which transferred near the corners. Ways to improve this point are discussed. However, our conclusion is that 3D-MID technology is an interesting technology for replacing the planar coils used in conventional WPT receivers

Omni-directional Inductive Wireless Power Transfer with 3D MID inductors

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Omni-directional Inductive Wireless Power Transfer with 3D MID inductors

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3D Plastronics for Smartly Integrated Magnetic Resonance Imaging Coils

International audienceOver the last four decades, magnetic resonance imaging has become the gold standard imaging technique in many medical diagnoses for brain, cardiac, and liver disease. However, due to low critical mass and great scientific challenges, instrumentation dedicated to preclinical MRI imaging has lagged behind instrumentation for clinical applications. The aim of this paper is to demonstrate that a set of new technologies such as the 3D Molded Interconnect Devices technology preferably named below as 3D Plastronics, 3D Printing, and Microfluidics may be considered to provide a completely new way for designing preclinical MRI setups, i.e., the 3D prototyping and manufacturing of the MR coil, the sample holder, and the peripherals, all together. The fabricated MRI setup can be used both for MRI of small biological samples and for in vivo imaging of a mouse brain. This work is the first step toward the full 3D manufacturing of tailor-mad multifunctional MRI probes

Omni-directional Inductive Wireless Power Transfer with 3D MID inductors

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