Michaël Gauthier

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.

Principle of a Submerged Freeze Gripper for Microassembly

The development of reliable and repeatable strategies to manipulate and assemble microobjects lies in the efficiency, reliability, and precision of the handling processes. In this paper, we propose a thermal-based microgripper working in an aqueous medium. Manipulating and assembling in liquid surroundings can indeed be more efficient than in dry conditions. A comparative analysis of the impact of dry and liquid media on surface forces, contact forces, and hydrodynamic forces is shown. In addition, ice grippers represent flexible manipulation solutions. Nevertheless, when micromanipulation tasks are performed in air, capillary forces can drastically perturb the release. Our submerged freeze microgripper exploits the liquid surroundings to generate an ice droplet to catch microobjects, and to avoid capillary forces during the release. The thermal principle, the first microgripper prototype, an ice generation simulation, and the first tests are presented. The main objective is to validate the manipulation principle. Further research will be focused on control and optimization of the ice generation and the miniaturization of the system.

High speed closed loop control of a dielectrophoresis-based system

Nanosciences have recently proposed a lot of proofs of concept of innovative nanocomponents and especially nanosensors. Going from the current proofs of concept on this scale to reliable industrial systems requires the emergence of a new generation of manufacturing methods able to move, position and sort micro-nano-components. We propose to develop `No Weight Robots-NWR that use non-contact transmission of movement (e.g. dielectrophoresis, magnetophoresis) to manipulate micro-nano-objects which could enable simultaneous high throughput and high precision. This article deals with a control methods which enables to follow a high speed trajectory based on visual servoing. The non-linear direct model of the NWR is introduced and the calculation of the inverted model is described. This inverted model is used in the control law to determine the control parameter in function of the reference trajectory. The method proposed has been validated on an experimental setup whose time calculation has been optimized to reach a control period of 1 ms. Future works will be done on the study of smaller components e.g. nanowires, in order to provide high speed and reliable assembly methods for nanosystems.

Capillary self-alignment assisted hybrid robotic handling for ultra-thin die stacking

Ultra-thin dies are difficult to package because of their fragility and flexibility. Current ultra-thin die integration technology for 3D microsystems relies on robotic pick-and-place machines and machine vision, which has rather limited throughput for high-accuracy assembly of fragile ultra-thin dies. In this paper, we report a hybrid assembly strategy that consists of robotic pick-and-place using a vacuum micro-gripper, and droplet self-alignment by capillary force. Ultra-thin dies with breakable links are chosen as part of the assembly strategy. Experimental results show that we can align ultra-thin (10μm) dies with sub-micron accuracy without machine vision. A fully automatic sequence of stacking several of these dies is demonstrated. Up to 12 ultra-thin dies have been stacked. These early results show that die-to-die integration of ultra-thin dies with higher throughput than the current industry robot is possible by applying both robotic handling and droplet self-alignment to ultra-thin die assembly.

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.

Optimization of the size of a magnetic microrobot for high throughput handling of micro-objects

One of the greatest challenges in microrobotic is to handle individually a large number of objects in a short time, for applications such as cell sorting and assembly of microcomponents. This ability to handle a large number of microobjects is directly related to the size of the microrobot. This paper proposes a theoretical study of the size of a magnetic microrobot maximizing its capacity of displacement. It demonstrates that there is an optimal size can be obtained, due to a trade-off between the inertial and the viscous effects. Analytical expressions of the optimal size and the related frequency of motion are derived from a simplified model to highlight the influence of the geometrical and the physical parameters of the magnetic manipulation system such as the viscosity of the liquid and the size of the workspace. A numerical simulation validates the analytical analysis and demonstrates a high displacement capacity of the microrobot (around 100 back and forth motions per second for a robot of around 20 μm).

Simulation and experiments on magnetic microforces for magnetic microrobots applications

Magnetic microrobots have a wide variety of applications in micro/nano-manipulation, micro/nano sensing and biomedical fields. Untethered magnetic microrobots are usually driven by a group of electromagnetic coils. To control the magnetic microrobots trajectory it is of utmost importance to know the magnitude of the magnetic force applied on them. In this paper finite element simulations are proposed to derive the magnetic field produced by an iron core coil. A three dimensional static magnetic analysis is also performed to simulate the magnetic force applied on a magnetic microrobot. The simulation results are validated by experimental measurements. A teslameter is used to measure the magnetic field on the central axis of the coil. A magnetic microrobot (less than 400 × 400 μm2) is fabricated and glued to a force sensor to measure the magnetic force applied on it. The measurement results are in good agreement with the simulation and show the effectiveness of the magnetic simulation.

Analysis and Specificities of Adhesive Forces Between Microscale and Nanoscale

Despite a large number of proofs of concept in nanotechnologies (e.g., nanosensors), nanoelectromechanical systems (NEMS) hardly come to the market. One of the bottlenecks is the packaging of NEMS which require handling, positioning, assembling and joining strategies in the mesoscale (from 100 nm to 10 μm, 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. First, it is shown that the distributions of charges observed on the micro-objects and meso-objects would have negligible effects on the nano-objects. Second, the impact of both chemical functionalization and physical nanostructuration on adhesion are presented. Third, the van der Waals forces are increased by local deformations on the mesoscale contrary to the nanoscale where the deformation is negligible. This paper shows some typical characteristics of the mesoscale.

Parallel microrobot actuated by capillary effects

This paper presents a new actuation mean for a parallel microrobot based on capillary effect, combining surface tension and pressure effects. The device presented is a compliant moving table having 6 degrees of freedom (dof) among which three are actuated: z axis translation having a stroke of a few hundreds of microns, and θx and θy tilt angles up to about 15°. The structure is immersed in a liquid and the actuation principle is based on fluidic parameters (pressure and volume). A model to calculate the stiffness of the system is presented and validated by experimental measurements. Some issues inherent to this type of actuation are also addressed. The presented device is an illustration of a promising solution for microrobotic actuation using capillary effects in a liquid media.