Joël Abadie

Smart Microrobots for Mechanical Cell Characterization and Cell Convoying

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.

Modeling Rearrangement Process of Martensite Platelets in a Magnetic Shape Memory Alloy Ni2MnGa Single Crystal under Magnetic Field and (or) Stress Action

The aim of the article is the modeling of the rearrangement process between martensite variants in order to use magnetic shape memory alloys (MSMs) as actuators. In the framework of the thermodynamics of irreversible processes, an efficient choice of the internal variables to take into account the magnetic and mechanical actions and a free energy function are stated. The behavior is chosen as magnetically reversible and mechanically irreversible. An equivalence between magnetic field action H and uniaxial stress action σ for the initiation of the rearrangement is established. Finally, model predictions are compared with experimental measurements.

Passive diamagnetic levitation: theoretical foundations and application to the design of a micro-nano force sensor

Mechanical friction and more generally adhesion forces are some problems, which can severely limit the performances of micromechanical devices. One way to avoid friction problem, is to use levitation methods. Levitation in static magnetic field is very easy to achieve by the use of diamagnetic materials. Thus, it is possible to freely suspend a light magnet and let it in a stable equilibrium state. We have developed a prototype of a micro-nano force sensor using a passive levitation approach. This paper explains diamagnetic levitation in the simple case of a small cylindrical magnet with a mass and volume of 11 mg and 1.65 mm/sup 3/ respectively. The forces applied to the suspended magnet are presented and the natural stability of the diamagnetic levitation is explained. Finally, we present the design of our micro-nano force sensor using diamagnetic levitation.

Levitated micro-nano force sensor using diamagnetic materials

Under suitable conditions, diamagnetic materials allow to achieve stable levitation of permanent magnets in entirely passive configuration. Using NdFeB magnets and diamagnetic materials such as graphite in a particular configuration, we build a passive levitated force sensor with a variable stiffness and linear output. The suspended part is used as the sensing device and two directions of force measurement are possible. The absence of friction makes the sensor highly sensitive and forces around nN can be measured. The established model of both magnetic and diamagnetic forces allows to calculate the applied force on the end point of the levitating device after measuring the position of the levitating part. This paper presents the description of the levitated sensor, force calculation and experimental results.

Original hybrid control for robotic structures using magnetic shape memory alloys actuators

Magnetic shape memory alloys (MSMA) are relatively new active materials but at this time they are not actually very used as actuators despite a high strain and a small response time. This is probably due in part to a large hysteresis and a strong non-linear behaviour. In this paper, an original hybrid control is designed taking into account dynamical effects and hysteretic behaviour in order to increase static gain of the system. After a short presentation of MSMA behaviour, a modelling is proposed to obtain two different control strategies. Some experimental results are also given.

Micromanipulation tasks using passive levitated force sensing manipulator

We present in this paper the development of a new kind of force sensing manipulator and use it to design a teleoperated micromanipulation station. The micromanipulation tasks are the two-dimensional positioning and forces interaction measurement of micrometer-size particles (50 /spl mu/m radius) in ambient condition. The manipulator used consists of a levitated glass probe with a tip of 20 /spl mu/m size. Since the levitation is achieved with totally passive approach, no control loop is then needed. Passive levitation is possible, under suitable conditions, using permanent magnets and diamagnetic materials. The established model of both magnetic and diamagnetic forces allows to calculate the applied force on the end-effector of the levitating device after measuring the position of the levitating part. The absence of friction forces and design configuration make the manipulator highly sensitive and forces around nN can be measured. This paper reports the description of the levitated sensing manipulator, model force calculation and experimental results of micromanipulation tasks.

Bending Model of an Integrated SMA Micro-Actuator

In this paper, we give a model of a Shape Memory Alloy (SMA) thin blade working in bending. This work is based on the general study and modeling of an integrated SMA micro-actuator called the “ module”, controled by thermoelectric effect. This module was developed in two versions. The first one is composed of a NiTi thin blade on which are placed two copper elements which play the role of heat sinks. Its temperature is controlled by Joule effect. In the second version, Bismuth Telluride ingots are used instead of copper elements. This second configuration allows the temperature control of the SMA blade by Peltier effect. The model of the bending behavior is based on a general macroscopic description of the thermomechanical behavior of SMA. The self-accommodating (pure thermal effect) and oriented (stress-induced) martensites are taken into account. The thermal boundary conditions used in this paper correspond to the first version of the micro-actuator. The numerical resolution by finite differences leads to the comprehension of phase transformation for pseudo-elastic and thermal cycling bending tests.

Nanoforce estimation based on Kalman filtering and applied to a force sensor using diamagnetic levitation

Nanoforce sensors based on passive diamagnetic levitation with a macroscopic seismic mass are a possible alternative to classical Atomic Force Microscopes when the force bandwidth to be measured is limited to a few Hertz. When an external unknown force is applied to the levitating seismic mass, this one acts as a transducer that converts this unknown input into a displacement that is the measured output signal. Because the under-damped and long transient response of this kind of macroscopic transducer cannot be neglected for time-varying force measurement, it is then necessary to deconvolve the output to correctly estimate the unknown input force. The deconvolution approach proposed in this paper is based on a Kalman filter that use an uncertain a priori model to represent the unknown nanoforce to be estimated. The main advantage of this approach is that the end-user can directly control the unavoidable trade-off that exists between the wished resolution on the estimated force and the response time of the estimation.

Nanoforce estimation with Kalman filtering applied to a force sensor based on diamagnetic levitation

Nano force sensors based on passive diamagnetic levitation with a macroscopic seismic mass are a possible alternative to classical Atomic Force Microscopes when the force bandwidth to be measured is limited to a few Hertz. When an external unknown force is applied to the levitating seismic mass, this one acts as a transducer that converts this unknown input into a displacement that is the measured output signal. Because the little damped and long transient response of this kind of macroscopic transducer can not be neglected, it is then necessary to deconvolve the output to correctly estimate the unknown input force. The deconvolution approach proposed in this article is based on a Kalman filter that use an uncertain a priori model to represent the unknown nanoforce to be estimated. The main advantage of this approach is that the end-user can directly control the unavoidable trade-off that exists between the wished resolution on the estimatedforce and the response time of the estimation.

Microforce sensor for microbiological applications based on a floating-magnetic principle

In this paper, we present the design of a new magnetic nano and microforce sensor for microbiological applications. The sensing part of the sensor presents a naturally stable six degrees of freedom equilibrium state using the combination of upthrust buoyancy and magnetic force. The sensor allows force measurement without deformation of the sensing element using a feedback control loop and is able to measure the components, in the horizontal plan, of the external force applied. The measurement range varies between around plusmn100 muN with a resolution of 20 nN and a linear output. The mechanical stiffness of the passive system is about 0.018 Nm-1 (same order of magnitude than an AFM micro-cantilever). A complete static study and experimental validation of the used principle are presented in this paper.