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

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

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

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

Chemical Biology of G-quadruplex and i-motif DNA: use of topologically constrained DNA

Tetrameric DNA structures such as G-quadruplex (G4) and i-motif (i-DNA) have attracted increasing interest in the last decades. They are indeed involved in many biological processes including translation regulation, pre-mRNA processing, mRNA targeting, telomere maintenance, etc. We have developed chemical tools named TASQ (Template-Assembled Synthetic Quadruplex) to address the following scientific goals: (i) identify unambiguous (i.e., affine and specific) G4- and i-DNA-interacting ligands, (ii) identify proteins interacting with those structures and determine their cellular relevance and (iii) select specific antibodies for G4 and i-DNA. This review reports on our works over the past decade

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

Adhesion control for Micro- and Nano-Manipulation.

International audienceThe adhesion between a micro=nano-object and a micro-gripper end-effector is an important problem in micromanipulation. Cancelling or reduction 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 pulloff force measurement 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

Overview of coupling effects on interaction forces in micro-nano-world.

International audienceThe release of object during robotic micromanipulation operations stays a challenge. The adhesion forces have to be known to improve micromanipulation tasks. Adhesion models build from macrophysics (continuum mechanics) or from nanophysics (atomic scale interactions) do not fit well experiments on the microscale. This is due to some phenomenon which are specific to the microphysics. Some of them are developed in this article. First, it is shown that the charges distributions observed on the microscale would have negligible effects on the nanoscale but disturbs significantly micromanipulation. Secondly, the impact of both chemical functionalisation and physical structuration of the surfaces on microscale are presented. Third, during the contact between two objects, the van der Waals forces induces significant local deformations on the microscale contrary to nanosclae where the deformation is negligible. This article shows some typical differences between microscale and nanoscale