Presentation and improvement of an AFM-based system for the measurement of adhesion forces.

International audienceThe aim of this paper is the presentation and improvement of an AFM-based system dedicated to measure adhesion forces. Because an AFM-lever presents a high linearity and a high resolution, it can be used to characterize forces that appears between two micro-objects when their relative distance is small. In this paper, an AFM is used to evaluate the adhesion forces versus the distance. Especially, the pull-off and the Van Der Waals forces can be quantified. Unfortunately, the presence of the hysteresis on the piezotube distorts the measurement and makes the whole system imprecise. Hence, a Prandtl-Ishlinskii hysteresis compensator is introduced. To show the efficiency of the improved measurement system, experiments on different materials where performed

Practical characterisation of the friction force for the positioning and orientation of Micro-Components.

International audienceThis paper deals with the description of a method for the measurement of friction force between a very small object (80 to 300 μm) and a support. The goal is to design a feeder based on controlled mechanical vibrations in order to drive microcomponents by breaking the friction force. The contact model is based on the Hertz theory and the Greenwood- Williamson multi-asperity model. The amplitude of the static friction force is measured in a clean environment with an AFM (Atomic Force Microscope) whose cantilever is placed in the vertical position. Using this setup and the modeling, we have estimated the interfacial shear stress between the microcomponent and the support

Improvement of robotic micromanipulations using chemical functionalisations.

International audienceRobotic microhandling is disturbed by the adhesion phenomenon between the micro-object and the grippers. This phenomenon is directly linked to both the object and the gripper surface chemical composition. We propose to control adhesion by using chemical self-assembly monolayer (SAM) on both surfaces. Previous distance-force measurements done with AFM have shown that the liquid pH can be used to modify the adhesion and created repulsive force between the gripper fingers and the micro-objet. This paper shows the correlation between the force distance distance measurements and the micromanipulation tasks using chemically functionalized grippers

Adhesion forces controlled by chemical self-assembly and pH. Application to robotic microhandling.

International audienceRobotic microhandling is a promising way to assemble microcomponents in order to manufacture new generation of Hybrid Micro ElectroMechanical Systems (HMEMS). However, at the scale of several micrometers, adhesion phenomenon highly perturbs the micro-objects release and the positioning. This phenomenon is directly linked to both the object and the gripper surface chemical composition. We propose to control adhesion by using chemical selfassembly monolayer (SAM) on both surfaces. Different types of chemical functionalisation have been tested and this paper focuses on the presentation of aminosilane grafted (3 (ethoxydimethylsilyl) propyl amine (APTES) and (3 aminopropyl) triethoxysilane (APDMES)). We show that the liquid pH can be used to modify the adhesion and to switch from an attractive behaviour to a repulsive behaviour. The pH control can thus be used to increase adhesion during handling and cancel adhesion during release. Experiments have shown that the pH control is able to control the release of a micro-object. This paper shows the relevance of a new type of reliable submerged robotic microhandling principle, which is based on adjusting chemical properties of liquid

Control of Adhesion using Surface Functionalisations for Robotic Microhandling.

International audienceRobotic microhandling is a promising way to assemble microcomponents in order to manufacture new generation of Hybrid Micro ElectroMechanical Systems (HMEMS). However, at the scale of several micrometers, adhesion phenomenon highly perturbs the micro-objects release and the positioning. This phenomenon is directly linked to both the object and the gripper surface mechanical and chemical properties. The control of the adhesion properties requires multidisciplinary approaches including roughness control, mechanical properties control and chemical surface functionalisation. We propose to control adhesion by using chemical surface functionalisations by intrinsic conducting polymer electrodeposition or Self-Assembly Monolayer (SAM) and using surface structuration

Robotic submerged microhandling controlled by pH swithching.

International audienceRobotic microhandling is a promising way to assemble microcomponents in order to manufacture new generation of Hybrid Micro ElectroMechanical Systems (HMEMS). However, at the scale of several micrometers, adhesion phenomenon highly perturbs the micro-objects release and the positioning. This phenomenon is directly linked to both the object and the gripper surface chemical composition. We propose to control adhesion by using chemical self-assembly monolayer (SAM) on both surfaces. Different types of chemical functionalisation have been tested and this paper only focuses on the presentation of aminosilane grafted (3 (ethoxydimethylsilyl) propyl amine (APTES) and (3 aminopropyl) triethoxysilane (APDMES)). We show that the liquid pH can be used to modify the adhesion and to switch from an attractive behaviour to a repulsive behaviour. The pH control can thus be used to increase adhesion during handling and cancel adhesion during release. Experiments have shown that the pH control is able to control the release of a micro-object. This paper shows the relevance of a new type of reliable submerged robotic microhandling principle, which is based an adjusting chemical properties of liquid

Analysis of forces for micromanipulations in dry and liquid media.

International audienceDuring microscale object manipulation, contact (pull-off) forces and non-contact (capillary, van der Waals and electrostatic) forces determine the behaviour of the micro-objects rather than the inertial forces. The aim of this article is to give an experimental analysis of the physical phenomena at a microscopic scale in dry and liquid media. This article introduces a review of the major differences between dry and submerged micromanipulations. The theoretical influences of the medium on van der Waals forces, electrostatic forces, pull-off forces and hydrodynamic forces are presented. Experimental force measurements based on an AFM system are carried out. These experiments exhibit a correlation better than 40 % between the theoretical forces and the measured forces (except for pull-off in water). Finally, some comparative experimental micromanipulation results are described and show the advantages of the liquid medium

Reduction of a micro-object's adhesion using chemical functionalisation.

International audienceThe adhesion and interaction properties of functionalised surfaces (substrate or cantilever) were investigated by means of atomic force microscope (AFM) related force measurements. The surfaces were functionalised with a polyelectrolyte: Poly(Allylamine Hydrochloride) (PAH), or with silanes: 3 (ethoxydimethylsilyl) propyl amine (APTES) or (3 aminopropyl) triethoxysilane (APDMES). Measurements of forces acting between a bare glass sphere (functionalised or not) and a functionalised surface indicated repulsive or attractive forces, depending on functionnalisation and medium (wet or dry). Adhesion forces (pull-off) can be observed in dry medium while in wet medium, this phenomenon can be cancelled. Now, the pull-off forces is an important problem in the automation of micro-object manipulations. The cancellation of this force by chemical functionnalisation is thus a promising way to improve micro-assembly in the future

Modeling of electrostatic forces induced by chemical surface functionalisation for microrobotics applications.

International audienceNon-contact microrobotics is a promising way to avoid adhesion caused by the well-known scale effects. Nowadays, several non-contact micro-robots exist. Most of them are controlled by magnetic or dielectrophoresis phenomena. To complete this, we propose a method based on electrostatic force induced by chemical functionalisation of substrates. In this study, we show a model of this force supported by experimental results. We reached long range forces measuring an interaction force of several microNewtons and an interaction distance of tens micrometers. This paper shows the relevance of using chemical electrostatic forces for microrobotics applications

Measurement of pull-off force for planar contact at the microscale.

International audienceAt the microscale, surface forces influence the behaviour of micro-objects more than volumic forces. During micro-assembly processes, contacts occur between a microgripper and a micro-object or between a substrate and a micro-object. The pull-off force, which represents the force required to break a contact, is one of the predominant problems in micro-assembly. Current force measurements are mostly focused on sphere-plane geometries, and models are based on naoscale theories. The aim of this Letter is to propose an evaluation of the pull-off force for a planar contact, which is the most frequent kind of contact in micro-assembly. Experimental force measurements based on a capacitive microforce sensor and micro/nano robotic systems are carried out. The proposed device enables the study of pull-off forces according to the preload force and the contact angle. Finally, experimental results are discussed and compared with a model