The robotic manipulation of microscopic objects is disturbed directly by the adhesion between the end-effector and the objects. In the micro scale, no reliable model of adhesion is available and currently the behaviour of the micro-objects cannot be predicted before experiments. This paper proposes a new model of adhesion based on the analytical resolution of the coupling between the mechanical deformation of the micro-objects and van der Waals forces. In the nanoscale, the impact of the deformation can be neglected and the proposed model is thus similar to the classical expression for van der Waals forces. In the microscale, the deformation induces van der Waals forces to increase significantly and a new analytical expression is proposed. The limit of validity of this 'deformable van der Waals forces' is also discussed. This result can be used as an alternative to classical adhesion-deformation models in literature (Johnson-Kendall-Roberts (JKR) or Derjaguin-Muller-Toporov (DMT)), which have been validated at the macroscale but are not sufficient to describ the interaction forces in the microscale (typically from 100 nm to 500 µm).

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-Despite a large number of proofs of concept in nanotechnologies (e.g. nanosensors), nano electromechanical systems (NEMS) hardly come to the market. One of the bottlenecks is the packaging of NEMS which requires handling, positioning, assembling and joining strategies in the mesoscale (from 100nm to 10µm, between nanoscale and microscale). It requires models of the interaction forces and adhesion forces dedicated to this particular scale. This paper presents several characteristics of the mesoscale in comparison with nanoscale and microscale. Firstly, it is shown that the distributions of charges observed on the micro-objects and meso-objects would have negligible effects on the nano-objects. Secondly, the impact of both chemical functionalisation and physical nanostructuration on adhesion are presented. Thirdly, the van der Waals forces is increased by local deformations on the mesoscale contrary to the nanoscale where the deformation is negligible. This article shows some typical characteristics of the mesoscale.Note to Practitioners -Micro and nanorobotics cover a high range from nanometers to micrometers which represents six orders of magnitude. Most of the microassembly activities have been focused on micro-objects whose size is 10 µm or more when nanohandling provides solutions mainly for nano-objects up to 100 nm. The interest in the medium scale (mesoscale) has been growing recently. This article presents an analysis of the behavioral characteristic of the objects on this scale in comparison with the two others. It shows that specificities exist on the mesoscale which show the requirement of original micro-nanorobotics at this particular scale.

The robotic manipulation of microscopic objects is disturbed directly by the adhesion between the endeffector and the objects. In the microscale, no reliable model of adhesion is available and currently the behaviour of the micro-objects cannot be predicted before experiments. This paper proposes a new model of adhesion based on the analytical resolution of the coupling between the mechanical deformation of the micro-objects and van der Waals forces. In the nanoscale, the impact of the deformation can be neglected and the proposed model is thus similar to the classical expression for van der Waals forces. In the microscale, the deformation induces van der Waals forces to increase significantly and a new analytical expression is proposed. The limit of validity of this 'deformable van der Waals forces' is also discussed. This result can be used as an alternative to classical adhesion-deformation models in literature (Johnson-Kendall-Roberts (JKR) or Derjaguin-Muller-Toporov (DMT)), which have been validated at the macroscale but are not sufficient to describ the interaction forces in the microscale (typically from 100 nm to 500 µm).