Patrick Rougeot

Analysis of forces for micromanipulations in dry and liquid media

During 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.

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

Robotic microhandling is a promising way to assemble microcomponents in order to manufacture a new generation of hybrid microelectromechanical systems. However, at the scale of several micrometers, the adhesion phenomenon highly perturbs the micro-object release and positioning. This phenomenon is directly linked to both the object and the gripper surface chemical composition. We propose to control the adhesion by using a chemical self-assembled monolayer on both surfaces. Different types of chemical functionalization have been tested, and this paper focuses on the presentation of aminosilane-grafted 3-(ethoxydimethylsilyl)propylamine and (3-aminopropyl)triethoxysilane. We show that the liquid pH can be used to modify the adhesion and to switch from an attractive behavior to a repulsive behavior. The pH control can thus be used to increase the adhesion during handling and cancel the 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 adjustment of the chemical properties of the liquid.

Forces analysis for micro-manipulation

The aim of this article is to give an experimental analysis of the physical phenomena at a microscopic scale. In particular, this article presents experimental measurements based on an AFM system. These experiments show the influence of the contact forces and distance forces especially for micromanipulation applications.

Adhesion Control for Micro- and Nanomanipulation

The adhesion between a micro/nano-object and a microgripper end-effector is an important problem in micromanipulation. Canceling or reducing this force is a great challenge. This force is directly linked to the surface chemical structure of the object and the gripper. We propose to predict this force between a structuring surface and a micro-object with a multisphere van der Waals force model. The surface was structured by polystyrene latex particles (PS particles) with radii from 35 to 2000 nm. The model was compared with experimental pull-off force measurements performed by AFM with different natures of spheres materials glued on the tipless. A wide range of applications, in the field of telecommunications, bioengineering, and more generaly speaking MEMS can be envisaged for these substrates.

Reducing the adhesion between surfaces using surface structuring with PS latex particle.

The adhesion between a micro-object and a microgripper end-effector is an important problem in micromanipulation. Canceling or reducing this force is a great challenge. This force is directly linked to the surface chemical structure of the object and the gripper. We propose to reduce the adhesion force by using a self-assembled monolayer structuring on one surface. The surface was structured by polystyrene latex particles (PS particles) with radii from 100 to 1500 nm. The adhesion force measurements obtained by AFM were compared to a multisphere van der Waals force model. The model suggests the existence of an optimal value of the sphere radius which minimizes the adhesion. In that case, the pull-off force is reduced to 20 nN by the PS particles layer with a radius of 45 nm. A wide range of applications in the field of telecommunications, bioengineering, and more generally speaking, MEMS can be envisaged for these substrates.

Synthesis, encapsulation, and performance analysis of large deformation tri-layer polypyrrole actuator

This paper reports the synthesis of an electroactive polymer actuator in polypyrrole (PPy) on a polyvinylidene difluoride (PVDF) substrate. The technological development is detailed. This study reports our investigation on a tri-layer PPy actuator for large deformations and comparison with literature modeling. We also investigate their use towards real applications by introducing lifetime measurement, encapsulation and closed loop control.

3D-Printing: A promising technology to design three-dimensional microsystems

System miniaturization remains an important challenge in the field of microrobotics. Several works have been raised in this context. Maybe the most known and widespread are MEMS devices based on clean room technologies. Although they give option to design small systems with mico/nano features, such technologies are limited to planar structures with two or three degrees of freedom (DOF). To tackle this limitation, a new approach is proposed in this paper. Instead of planar construction, we proposed here to design three-dimensional micro-systems by taking advantages of additive manufacturing technology, namely 3D printing. The final objective consists to design a monolithic structure in one operation without assembly. Then functionalization could be achieved by equipping the structure with actuators and sensors. Starting from the fact that any complex structure could be decomposed into basic elements such as articulations or flexures, this paper will focus on how articulations could be fabricated without assembly using 3D printing facilities. Combining those articulations which are considered as fundamental bricks will make possible to design complex monolithic structures. As an illustration, a pivot articulation is experimentally demonstrated using 3D printing.

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

Non-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.

Improvement of Robotic Micromanipulations Using Chemical Functionalisations

Robotic 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.

Robotic submerged microhandling controlled by pH swithching

Robotic 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.