F. Mathieu - Academia.edu (original) (raw)

Papers by F. Mathieu

Sensors and Actuators B: Chemical, 2015

In the absence of coating, the only way to improve the sensitivity of silicon microcantilever-bas... more In the absence of coating, the only way to improve the sensitivity of silicon microcantilever-based density sensors is to optimize the device geometry. Based on this idea, several microcantilevers with different shapes (rectangular-, U-and T-shaped microstructures) and dimensions have been fabricated and tested in the presence of hydrogen/ nitrogen mixtures (H 2 /N 2) of various concentrations ranging from 0.2% to 2%. In fact, it is demonstrated that wide and short rectangular cantilevers are more sensitive to gas density changes than U-and T-shaped devices of the same overall dimensions, and that the thickness doesn't affect the sensitivity despite the fact that it affects the resonant frequency. Moreover, because of the phase linearization method used for the natural frequency estimation, detection of a gas mass density change of 2 mg/l has been achieved with all three microstructures. In addition, noise measurements have been used to estimate a limit of detection of 0.11 mg/l for the gas mass density variation (corresponding to a concentration of 100 ppm of H 2 in N 2), which is much smaller than the current state of the art for uncoated mechanical resonators.

Microelectronic Engineering, 2008

For the purpose of biochip miniaturization, we developed a liquid spotter-based on silicon microc... more For the purpose of biochip miniaturization, we developed a liquid spotter-based on silicon microcantilevers incorporating in-plane nanotips as a MEMS nanopatterning tool. We present new fabricated cantilevers with added piezoresistors for the contact force control during deposition. Matrices of droplets of 1 lm in diameter were achieved with a 10 lm interspot distance with high uniformity and high reproducibility by the nanotip cantilever with piezoresistive force controller.

IEEE Transactions on Circuits and Systems I: Regular Papers, 2009

A low-power multi-channel CMOS digital read-out IC (ROIC) for differential piezo-resistive sensin... more A low-power multi-channel CMOS digital read-out IC (ROIC) for differential piezo-resistive sensing is presented as part of the positioning system of a liquid dispensing MEMS. New very low-voltage and single-battery compatible CMOS circuits are proposed for digital gain tuning, pre-amplification and integrating A/D conversion. Overall low-power consumption is achieved by operating the key devices in subthreshold in order to prevent from heating the fluidic MEMS. A complete quadchannel ROIC has been integrated in 0.35µm CMOS 2-polySi 4-metal technology. The reported experimental results agree with the electrical simulations. Index Terms-Piezo-resistive sensors, CMOS interface circuits, analog-to-digital (A/D) conversion, pulse density modulation (PDM), micro-electro-mechanical systems (MEMS).

Sensors and Actuators A: Physical, 2005

We have developed an integrated and compact microdevice consisting of piezoresistive microcantile... more We have developed an integrated and compact microdevice consisting of piezoresistive microcantilevers with a dedicated electronic readout. This microdevice designed for force sensor applications can also be used in atomic force microscopy for parallel operation without an optical detection scheme. The system features a 1.25 V/m resolution with 10 mV noise.

MOSFET and ChemFET are currently being used in many types of applications for the measurement of ... more MOSFET and ChemFET are currently being used in many types of applications for the measurement of electrochemical potential and pH in liquid phase. This paper presents the realization of an analysis micro device including the micro sensor chip, the on-board electronic and the associated fluidics. The whole micro system can be easily transported, used for cellular cultures monitoring or chemical test thanks to a specific electronic interface. Using the transistor saturation mode, this interface enables both static and dynamic measurements for ChemFET and MOSFET-based devices, reducing electrical measurement interferences (up to 50dB) coming from the liquid phase.

Scientific Reports, May 22, 2018

Journal of the American Chemical Society, Jan 19, 2018

Molecular spin crossover complexes are promising candidates for mechanical actuation purposes. Th... more Molecular spin crossover complexes are promising candidates for mechanical actuation purposes. The relationships between their crystal structure and mechanical properties remain, however, not well understood. In this study, combining high pressure synchrotron X-ray diffraction, nuclear inelastic scattering and micromechanical measurements we assessed the effective macroscopic bulk modulus (B = 11.5 ± 1.5 GPa), Young's modulus (Y = 10.9 ± 1.0 GPa) and Poisson's ratio (ν = 0.34 ± 0.04) of the spin crossover complex [FeII(HB(tz)3)2] (tz = 1,2,4-triazol-1-yl). Crystal structure analysis revealed a pronounced anisotropy of the lattice compressibility, which was correlated with the difference in spacing between the molecules as well as by the distribution of the stiffest C-H···N interactions in different crystallographic directions. Switching the molecules from the low spin to the high spin state leads to a remarkable drop of the Young's modulus to 7.1 ± 0.5 GPa both in bulk a...

Proceedings

We show that nanometer-scale dielectric thin films can act as efficient electromechanical transdu... more We show that nanometer-scale dielectric thin films can act as efficient electromechanical transducers to simultaneously drive and sense the vibration of the first flexural mode of micro/nano-cantilevers. Here, 16 μm-long, 5 μm-wide and 350 nm-thick cantilevers are actuated by a 15 nm-thick silicon nitride layer, and electrically detected by charge measurement at megahertz frequencies. The displacement was also checked by optical interferometry, and the electromechanical transduction efficiency is extracted and compared to an analytical modelling.

Angewandte Chemie (International ed. in English), Jan 10, 2017

We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of ... more We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)3 )2 ] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex. The strong mechanical coupling was also evidenced by the decrease of approximately 66 Hz in the resonance frequency in the high-spin state as well as by the drop in the quality factor around the spin transition.

Applied Physics Letters, 2016

Silicon MEMS cantilevers coated with a 200 nm thin layer of the molecular spin crossover complex ... more Silicon MEMS cantilevers coated with a 200 nm thin layer of the molecular spin crossover complex [Fe(H2B(pz)2)2(phen)] (H2B(pz)2 = dihydrobis(pyrazolyl)borate and phen = 1,10-phenantroline) were actuated using an external magnetic field and their resonance frequency was tracked by means of integrated piezoresistive detection. The light-induced spin-state switching of the molecules from the ground low spin to the metastable high spin state at 10 K led to a well-reproducible shift of the cantilever's resonance frequency (Δfr = −0.52 Hz). Control experiments at different temperatures using coated as well as uncoated devices along with simple calculations support the assignment of this effect to the spin transition. This latter translates into changes in mechanical behavior of the cantilever due to the strong spin-state/lattice coupling. A guideline for the optimization of device parameters is proposed so as to efficiently harness molecular scale movements for large-scale mechanical work, thus paving the road for nanoelectromechanical systems (NEMS) actuators based on molecular materials.

Frontiers in Mechanical Engineering, 2016

Sensors and Actuators B: Chemical, 2014

A hybrid circuit of a transistor-based chip was implemented and characterized for the neuronal el... more A hybrid circuit of a transistor-based chip was implemented and characterized for the neuronal electrical activity recording. The integration of microfluidic architectures was developed to control precisely neurites outgrowth and form topologically defined and stable neural networks. Individual neural cells from rat retinae and Lymnaea stagnalis snails were immobilized on gates regions of Metal Insulator Semiconductor Field Effect Transistors (MISFET). Neuronal orientation was achieved in both cases but neuronal action potentials were only recorded in the Lymnaea stagnalis case. They were successfully triggered and inhibited by implementing a picrotoxin-GABApicrotoxin injection protocol, exhibiting a direct influence of picrotoxin on the "spike type" action potential waveform. The implementation of the whole process of neuronal culture and subsequent activity monitoring constitutes a proof-of-principle experiment for the development of neuroelectronic systems for signal processing studies adapted to low-density neuronal cultures.

Journal of Microelectromechanical Systems, Oct 1, 2008

This paper introduces a picoliter droplet dispenser relying on an array of silicon microcantileve... more This paper introduces a picoliter droplet dispenser relying on an array of silicon microcantilevers. The microcantilevers bear fluidic channels, and liquid transfer is achieved by a direct contact of the cantilever tip and the surface. A high degree of control over the location and geometry of the fabricated patterns is ensured by incorporating force sensors and electroassisted deposition means, i.e., electrowetting actuation and electrospotting, to the devices. The cantilever array, a PC-controlled stage, and an electronic circuit dedicated to the piezoresistance measurements form a closed-loop system that enables the automatic displacement of the array and the control of the deposition parameters. By using an external loading chip, different liquids are loaded onto the cantilevers, enabling the parallel deposition of several entities in a single spotting run. This paper details the design of the cantilevers assisted by finite-element modeling, the fabrication of the cantilever array, and the closed-loop operation. Moreover, proof-of-concept experiments are presented to demonstrate the versatility of our deposition system in terms of deposited materials and spot sizes. The control of the spotting process, the versatility of the printed materials, and the added electroassisted features prove that this tool has a real potential for research work and industrial applications.

Nanoscience &Nanotechnology-Asia, 2015

2010 IEEE International Frequency Control Symposium, 2010

Sensing platforms (5mm*5mm) containing 5 piezoelectric membranes have been fabricated by standard... more Sensing platforms (5mm*5mm) containing 5 piezoelectric membranes have been fabricated by standard micromachining techniques starting with a Silicon-On-Insulator wafer. Each membrane (circular, with radius varying from 360 microns to 440 microns) could be individually actuated through a PZT 1-micron thick film and sensed either via the same piezoelectric patch or via two terminal piezoresistances (obtained by boron implantation) placed at high-stress location onto the devices. Specific associated electronics (bandwidth of 2 MHz) have been designed and realized so that multiplexed actuation and sensing of all membranes resonant frequencies can be performed either in open-loop or closed-loop mode.

Electroactive Polymer Actuators and Devices (EAPAD) 2015, 2015

Despite a growing interest in conducting polymer based actuators, a robust fabrication technique ... more Despite a growing interest in conducting polymer based actuators, a robust fabrication technique is still needed. We suggest a fabrication method that allows fast production of conducting polymer actuators from commercially available polyvinylidene flouride membranes (PVDF) and a PEDOT/PSS solution. In order to improve adhesion of those materials, Ar plasma induced grafting is used to create hydrophilic surfaces of up to 40 μm. Hydrophilic PVDF-graft-polyethylene glycol allows diffusion of PEDOT/PSS in the pores of the membranes, while hydrophobic middle layers prevent short circuits. In this way, soft actuators can be fabricated by consequent drop casting and drying of conducting polymer.

2008 IEEE International Symposium on Circuits and Systems, 2008