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 article presents a new micro and nanoforce sensor used to perform a mechanical characterisation of human oocytes. This device is based on the use of low-stiffness magnetic springs. The oocytes ...to be characterised are placed on a force–sensitive platform. A manipulator equipped with a standard micropipette is used to mechanically compress the oocyte. Some complete “force–compression length” curves associated with mechanical load–unload cycles are given. These curves show the linear, the non-linear and also the plastic mechanical behaviour of the oocytes. These characterisations must be considered as a preliminary result which illustrates that the mechanical variability and the mechanical evolution of human oocytes during their maturation process can be observed with a force sensor based on magnetic springs.
•Design of micro and nanoforce sensor based on macroscopic seismic mass.•Magnetic springs for micro and nanoforce measurement.•Force sensor based on the use of the magnetic instability of a magnetic ...spring.•Application to the mechanical characterisation of human oocytes.
This article presents a novel low cost force sensing platform for the mechanical characterisation of human oocytes. This platform is compatible with the specific context of Assisted Reproductive Technology (ART). The oocyte is placed inside a standard Petri dish filled with a culture medium. It is immobilized using a holding pipette. The disposable parts used to mechanically test each oocyte are made of glass. This configuration is very similar to the one used in IntraCytoplasmic Sperm Injection protocol excepted that the injection pipette is replaced by a glass indenter. This platform uses two passive and linear magnetic springs to measure the nanoforce applied to the oocyte. The stabilisation of the unstable magnetic springs is passively achieved using the reaction force generated by the compressed oocyte. Some preliminary results obtained with an experimental platform are presented. The global magnetic stiffness of the indenter, evaluated by simulation and experimentally identified, is about 0.0013Nm−1.
Biological research requires new tools for cell micromanipulations. Currently, biological cell sizes range from a few to hundreds of micrometers, their manipulation therefore belonging to the field ...of microrobotics. This paper presents a new wireless micromanipulation system which allows cells placed in a droplet of liquid to be pushed on a glass slide. The cell micropusher is a ferromagnetic object which follows the movement of a permanent magnet located under the glass slide. It has been proved in previous works that two kinds of micropusher movements can induce a movement of the pushed object: turning the micropusher around the contact point (rotation), or moving the micropusher in translation. Rotation allows an object to be placed with a precision below 1 /spl mu/m, but acts within a narrow range. Translation allows placement of an object with lower accuracy, but within a wide range. We propose a specific coarse-fine control strategy to push an object, with good precision, within a wide range. Furthermore, experimentation on polystyrene balls of 50 /spl mu/m in diameter, and immature human oocytes of 150 /spl mu/m in diameter are presented. Note to Practitioners-Biological research requires new tools for cell micromanipulations. Currently, biological cell sizes range from a few hundred micrometers; their manipulation, therefore, belongs to the field of microrobotics. This paper presents a new wireless micromanipulation system which allows cells placed in a droplet of liquid to be pushed on a glass slide. The cell micropusher is a ferromagnetic object which follows the movement of a permanent magnet located under the glass slide. It has been proven in previous works that two kinds of micropusher movements can induce a movement of the pushed object: turning the micropusher around the contact point (rotation), or moving the micropusher in translation. Rotation allows an object to be placed with a precision below 1 /spl mu/m, but acts within a narrow range. Translation allows placement of an object with lower accuracy, but within a wide range. We propose a specific coarse-fine control strategy to push an object, with good precision, within a wide range. Furthermore, experimentation on polystyrene balls of 50 /spl mu/m in diameter, and immature human oocytes of 150 /spl mu/m in diameter are presented.
This paper is focused on the design and modeling of a new micro and nano force sensor using magnetic springs. The force sensitive part is a macroscopic horizontal rigid platform used as a floating ...seismic mass. This platform presents a naturally stable equilibrium state for its six degrees of freedom (dof) thanks to the combination of upthrust buoyancy and magnetic forces. This force sensor allows the measurement of the external horizontal force and the vertical torque applied to the platform. Thanks to the magnetic springs configuration used, the seismic mass presents a 0.02
N/m horizontal mechanical stiffness (similar to the stiffness of a thin AFM micro-cantilever). The measurement range typically varies between ±50
μN. The resolution depends on the displacement sensors used to measure the seismic mass displacement and on the environmental conditions (ground, liquid and air vibrations). In steady state, this displacement is proportional to the applied force. Resolution of less than 10
nN can be reached with the use of an anti-vibration table.
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 presents a new control method devoted to improve the performances of 2-DOF piezoelectric actuator for precise positioning tasks. The piezoelectric actuator exhibits strong cross-couplings ...between its two axes and strong hysteresis and creep nonlinearities. These unwanted phenomena undeniably compromised therefore the final precision of the targeted tasks (micromanipulation) and should be conveniently accounted during the controller synthesis. In this paper, we proposed a combination of the discrete linear Kalman filtering with a closed-loop scheme to suppress the effects of the couplings and of the nonlinearities. The suggested method permits to improve the performances of the piezoelectric actuator without specific and detailed characterization and knowledges on the hysteresis and on the creep models. Extensive experiments were carried out with complex desired trajectories and demonstrate the efficiency of the novel approach.
This paper presents a control scheme regarding to improve the performances of a piezoelectric actuator (PEA) for precise positioning tasks. The piezoelectric actuator exhibits strong nonlinear ...disturbances for 1- and 2-DOF motion, i.e. input-dependent hysteresis, creep and cross-couplings. These unwanted phenomena undeniably compromise the final precision of the targeted tasks (micromanipulation) and therefore it should be conveniently considered during the controller synthesis. In this regard, the dynamic equation is also split into a nominal model and a uncertain model including parametric uncertainties. We propose to use simultaneously a the discrete linear extended-state linear Kalman filter (ES-LKF), to estimate the aforementioned disturbances and the velocity, and Lyapunov-based controller to guarantee asymptotic stability while meeting the actuator limits. The proposed strategy permits to perform accurate positioning, for regulation and trajectory-tracking tasks, without a prior knowledge of parametric and unmodeled uncertainties. Real-time experiments were carried out with circular trajectories to demonstrate the efficiency of the proposed approach.
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).
We present a survey of fish-like propulsion at millimeter scale in order to build high efficiency swimming microrobots. We begin with a mechanical study of the fish-like propulsion. The mechanical ...model we used shows that undulatory motions are more efficient than oscillatory motions. We applied these theoretical results to the design and the realization of a microrobot propelled by the beating of two fins. Fins are moved by a transducer material called IPNC (ionic polymer composite metal). The experimental results allow us to check our theoretical model of the microrobot. Finally, we propose an improved microrobot which would have a better efficiency.
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