This paper is focused on the study of a new low frequency micro and nanoforce sensor based on diamagnetic levitation. The force sensitive part is a 10-cm long macroscopic capillary tube used as a ...levitating seismic mass. This tube presents a naturally stable equilibrium state with six degrees of freedom thanks to the combination of diamagnetic repulsive and magnetic attractive forces. It is only used as a one-direction force sensing device along its longitudinal axis. This force sensor is passive. The force measurement is based on the displacement of the capillary tube and in steady-state this displacement is proportional to the force. This sensor is characterized by an under-damped second-order linear force–displacement dynamic which remains linear on several hundred micrometers and can thus measure a wide range of microforces. Because of the magnetic springs configuration used, the capillary tube presents a horizontal mechanical stiffness that can be adjusted between 0.01 and 0.03
N/m (similar to the stiffness of a thin AFM cantilever). The measurement range typically varies between ±50
μN. Bandwidth is 4
Hz. The resolution depends on the sensor used to measure the capillary tube displacement and on noises induced by environmental conditions (ground and air vibrations). The resolution typically reached with a STIL confocal chromatic sensor is 5
nN inside a test chamber located on a anti-vibration table. This study is illustrated by a pull-off force measurement.
This paper presents a new method developed for the optimal design of piezoactive compliant micromechanisms. It is based on a flexible building block method, called FlexIn (flexible innovation), which ...uses an evolutionary approach, to optimize a truss-like planar structure made of passive and active building blocks, made of piezoelectric material. An electromechanical approach, based on a mixed finite-element formulation, is used to establish the model of the active piezoelectric blocks. From the first design step, in addition to conventional mechanical criteria, innovative control-based metrics can be considered in the optimization procedure to fit the open-loop frequency response of the synthesized mechanisms. In particular, these criteria have been drawn here to optimize modal controllability and observability of the system, which is particularly interesting when considering control of flexible structures. Then, a planar monolithic compliant microactuator has been synthesized using FlexIn and prototyped. Finally, simulations and experimental tests of the FlexIn optimally synthesized device demonstrate the interests of the proposed optimization method for the design of microactuators, microrobots, and more generally for adaptronic structures.
This paper deals with the effective design of smart microrobots for both mechanical cell characterization and cell convoying for in vitro fertilization. The first microrobotic device was developed to ...evaluate oocyte mechanical behavior in order to sort oocytes. A multi-axial micro-force sensor based on a frictionless magnetic bearing was developed. The second microrobotic device presented is a cell convoying device consisting of a wireless micropusher based on magnetic actuation. As wireless capabilities are supported by this microrobotic system, no power supply connections to the micropusher are needed. Preliminary experiments have been performed regarding both cell transporting and biomechanical characterization capabilities under in vitro conditions on human oocytes so as to demonstrate the viability and effectiveness of the proposed setups.
This paper deals with the development of an open design platform for explorative cell mechanotransduction investigation. The produced setup combines scanning probe microscopy (SPM) techniques and ...advanced robotics approaches, allowing both prolonged observations and spatial measurements on biological samples. As a result, an enhanced force probing method based on scanning microscopy techniques and advanced robotics and automation approaches is integrated in this device. Visual and force feedback control is used to achieve automatic data acquisition and monitoring processes when high skills are required. Experimentation on the mechanical cell characterization under in vitro conditions on human adherent cervix epithelial Hela cells are presented to demonstrate the viability and effectiveness of the proposed setup.
In this paper, modeling and robust control strategy for a new control-optimized piezoelectric microgripper are presented. The device to be controlled is a piezoelectric flexible mechanism dedicated ...to micromanipulation. It has been previously designed with an emphasis to control strategy, using a new topological optimization method, by considering innovative frequency-based criteria. A complete nonlinear model relating the voltage and the resulting deflection is established, taking into account hysteresis as a plurilinear model subjected to uncertainties. The approach used for controlling the actuator tip is based on a mixed high authority control (HAC)/low authority control (LAC) strategy for designing a wideband regulator. It consists of a positive position feedback damping controller approach combined with a low-frequency integral controller, which is shown to have robustness performances as good as a RST-based robust pole placement approach for the microgripper. The rejection of the vibrations, naturally induced by the flexible structure, and the control of the tip displacement have been successfully performed. Because we had taken into account frequency-based criteria from the first designing step of our device, we demonstrate that the tuning of the HAC/LAC can be easily performed and leads to low-regulator order.
The Micromanipulation and Micro-actuation Research Group at the LAB has activities related to biological and surgical applications. Concerning cells micromanipulation, our laboratory works in ...collaboration with the research team "Genetic and Reproduction" of the Besançon's hospital (France). The global final objective is the development of an automatic intra cytoplasmic sperm injection (ICSI) device in order to improve performances and ergonomics of current devices. In the future this new device will contain various modules: module for removal of cumulus cells, modules for characterization of oocytes, microinjection module, cells transport system. The first subsystem developed is a new single cell transport system. It consists in a so-called micropusher which pushes single cells without having contact with the external environment. This micropusher is a ferromagnetic particle (from 400 x 400 x 20 microm3 to 100 x 100 x 5 microm3) which follows the movement of a permanent magnet located under the biological medium. A 2D micro-positioning table moves this magnet under the glass slide. The pusher and cells positions are measured through an optical microscope with a CCD camera located above the biological medium. The second subsystem is developed to measure oocytes mechanical stiffness in order to sort them. We have then developed a micro/nano-force sensor based on the diamagnetic levitation principle: a glass tip end-effector (with 20 microm in diameter) is fixed on the equipment which is in levitation (0.5 mm in diameter, 100 mm in length). When a force is applied to the levitated glass tip, it moves to a new equilibrium position. Thanks to themeasurement of this displacement, the applied force can be measured. Since there is no contact and friction between the levitated tip and the fixed part, the resolution of this sensor is very high (10 nN).
The paper deals with the design, calibration and experimental validation of a novel infrastructure-less solution dedicated to indoor pedestrian localisation issues. The approach involves aerodynamic ...fluid computation for instantaneous speed estimation of a pedestrian handling a smartphone. For this purpose, a differential pressure-based MEMS anemometer is integrated to an Android smartphone by means of a dedicated PIC 32 bits microcontroller. Measurements of the pedestrian orientation are ensured by a gyroscope sensor coupled with the smartphone. Consequently, both instantaneous speed and heading measurements are combined to the dead reckoning technique for estimating the 2D relative position of the user. Theoretical modeling is conducted in order to calibrate and quantify the accuracy of the sensor. In situ experiments along straight paths demonstrate that the sensors coupled with a smartphone achieve pedestrian localisation with average accuracy of less than 6 % of the total travelled distance.
We present a novel force sensor designed to facilitate force measurement deployment in various applications such as load cells or force sensitive surfaces. This force sensor can indeed inherently ...sense out-of-plane forces. It is a monolithic structure that integrates two resonators and provides a steady area. If a perpendicular force is applied on this steady area, a frequency shift of the two resonators occurs. The amount of force applied can thus be estimated by monitoring the frequency of the resonators. As a proof of concept, we report the fabrication and experimental characterization of a first prototype. Under atmospheric pressures, our prototype currently offers a quality factor of ∼700, and a linear displacement sensitivity of ∼5.75Hz/μm. In addition, we report the implementation of a compact and low-cost optical fiber setup to monitor the resonators’ frequency.
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