Jean-Marc Breguet

In Situ Electron Microscopy Mechanical Testing of Silicon Nanowires Using Electrostatically Actuated Tensile Stages

Two types of electrostatically actuated tensile stages for in situ electron microscopy mechanical testing of 1-D nanostructures were designed, microfabricated, and tested. Testing was carried out for mechanical characterization of silicon nanowires (SiNWs). The bulk micromachined stages consist of a comb-drive actuator and either a differential capacitive sensor or a clamped-clamped beam force sensor. High-aspect-ratio structures (height/gap = 20) were designed to increase the driving force of the geometrically optimized actuator and the sensitivity of the capacitive sensor. The actuator stiffness is kept low to enable high tensile force to be exerted in the specimen rather than in the suspensions of the comb drive. Individual SiNWs were mounted on the devices by in situ scanning electron microscopy nanomanipulation, and their tensile properties were determined to demonstrate the device capability. The phosphorus-doped SiNWs, which were grown in a bottom-up manner by the vapor-liquid-solid process, show an average Youngs modulus of (170.0 ± 2.4) GPa and a tensile strength of at least 4.2 GPa. Top-down electroless chemically etched SiNWs, with their long axis along the [100] direction, show a fracture strength of 5.4 GPa.

Applications of Piezo-Actuated Micro-Robots in Micro-Biology and Material Science

This paper presents a few examples of manipulators and micro-robots based on piezo-actuators developed in the Laboratoire de Systemes Robotiques (LSRO) at EPFL. Three working principles was described (bender, inch-worm, inertial drives) and illustrated through examples for various applications (neurology, microbiology, electro discharge machining, nano-material testing and assembly of carbon nanotubes). Our goal is to demonstrate that an innovative mechanical design can make it possible to realize extremely simple manipulators working in the nanometer range for applications in micro-biology and nanotechnologies.

Micropositioners for microscopy applications based on the stick-slip effect

Piezo actuators are widely used for precision positioning purposes where a submicron resolution is needed. Among the possible means to increase the working range of those actuators whose stroke is, depending on the material, usually limited to a small fraction of the actuator length, is a stepping motion of the actuator. We use a stepping motion based on the stick and slip effect in order to achieve a long range while maintaining the advantage of a virtually unlimited resolution. In this paper we introduce miniature x-y-stages dedicated to the manipulation of samples under a microscope. As previous setups and experiments have shown, a parallel kinematic structure for positioning purposes in microscopy or micro assembly is not well suited because x and y motion of the actuators have an influence on each other. A system with a serial kinematic structure has therefore been developed. The proposed device will provide the same capabilities as existing motorized stages, but at a lower cost than manual positioning stages and at a very compact size.

Issues in precision motion control and microhandling

Illustrates with various practical examples an activity at the intersection of MEMS, system control, robotics and ultraprecision design. The resulting new application domains include microrobotics, microfactories and nanotechnologies.

A high-sensitivity and quasi-linear capacitive sensor for nanomechanical testing applications

The design, modeling, fabrication and characterization of triplate differential capacitive sensors employed in novel on-chip tensile and compression material testing systems are reported, where the capacitive sensors are integrated to measure the load on the specimen or the specimen deformation. Analytical expressions for studying stability, linearity and sensitivity, including the effect of the electrostatic force generated by the excitation signal on the sensing electrodes, are derived for the first time and discussed for quasi-static applications. The possible influence of the electron beam of an electron microscope on the capacitance measurement is also analyzed. The in-plane suspension stiffness of the fabricated device is determined by a resonance method performed inside a scanning electron microscope and used for pull-in voltage prediction. Sensitivity and linearity are extracted from capacitance-to-displacement measurements and agree well with analytical and finite element analysis results. The fabricated capacitive sensors show a high sensitivity of 0.61 fF nm−1 within a quasi-linear moving range of 2250 nm, which yields a displacement resolution of 1 nm and a load resolution of 34 nN.

Microvision system (MVS): a 3D computer graphic-based microrobot telemanipulation and position feedback by vision

The aim of our project is to control the position in 3D-space of a micro robot with sub micron accuracy and manipulate Microsystems aided by a real time 3D computer graphics (virtual reality). As Microsystems and micro structures become smaller, it is necessary to build a micro robot ((mu) -robot) capable of manipulating these systems and structures with a precision of 1 micrometers or even higher. These movements have to be controlled and guided. The first part of our project was to develop a real time 3D computer graphics (virtual reality) environment man-machine interface to guide the newly developed robot similar to the environment we built in a macroscopic robotics. Secondly we want to evaluate measurement techniques to verify its position in the region of interest (workspace). A new type of microrobot has been developed for our purposed. Its simple and compact design is believed to be of promise in the microrobotics field. Stepping motion allows speed up to 4 mm/s. Resolution smaller than 10 nm is achievable. We also focus on the vision system and on the virtual reality interface of the complex system. Basically the user interacts with the virtual 3D microscope and sees the (mu) -robot as if he is looking through a real microscope. He is able to simulate the assembly of the missing parts, e.g. parts of the micrometer, beforehand in order to verify the assembly manipulation steps such assembly of the missing parts, e.g. parts of a micromotor, beforehand in order to verify the assembly manipulation steps such as measuring, moving the table to the right position or performing the manipulation. Micro manipulation is form of a teleoperation is then performed by the robot-unit and the position is controlled by vision. First results have shown, that a guided manipulations with submicronics absolute accuracy can be achieved. Key idea of this approach is to use the intuitiveness of immersed vision to perform robotics tasks in an environment where human has only access using high performing measurement and visualization systems. Using also the virtual scene exactly reconstructed from the CAD-CAM-databases of the real environment being considered as the a priori knowledge, human observations and computer-vision based techniques the robustness and speed of such a simulation can be improved tremendously.

Comparison of nanoindentation results obtained with Berkovich and cube-corner indenters

There is increasing interest in using sharp cube-corner indenters in nanoindentation experiments to study plastic properties. In combination with finite element methods, it is, for example, possible to extract stress–strain curves from load–displacement curves measured with differently shaped pyramidal indenters. Another example is the fracture toughness of coatings, which can be studied using cracks produced during indentation with cube-corner tips. We have carried out indentation experiments with Berkovich and cube-corner indenters on eight different materials with different mechanical properties. To gain information about the formation of pile-up and cracks, indentation experiments with cube-corner indenter were performed inside a scanning electron microscope (SEM) using a custom-built SEM-microindenter. The results show that reliable hardness and modulus values can be measured using cube-corner indenters. However, the fit range of the unloading curve has a much bigger influence on the results for the cube-corner than for the Berkovich tip. The unloading curves of a cube-corner measurement should, therefore, be carefully inspected to determine the region of smooth curvature, and the unloading fit range chosen warily. Comparison of the modulus results shows that there is no significant difference between cube-corner and Berkovich measurements. Also for hardness, no fundamental difference is observed for most of the investigated materials. Exceptions are materials, such as silicon nitride, cemented carbide or glassy carbon, where a clear difference to the hardness reference value has been observed although the modulus difference is not pronounced.

Piezoactuators for motion control from centimeter to nanometer

This paper presents several approaches for piezoactuators in motion control over a large dynamic range (cm to nm). The devices include monolithic two-degree-of-freedom actuators with mechanical amplification, stick-slip actuators and 6-DOF designs of micro-positioners. Closed loop feedback is of course necessary for good performance. All the proposed solutions have been realized and experimental results are discussed, application examples in scanning probe microscopy and biology are shortly presented.

Micro/nanofactory : Concept and state of the art

A Microfactory is a set of cooperating micro-machines dedicated to the production of Microsystems in small to medium quantities. This paper describes the Microfactory concept currently developed at the Institut de Systemes Robotiques (ISR). A state of the art in this domain is presented. Several novel designs on micro-positioning systems are discussed. Emphasis is put on piezo-actuators with nanometer resolution and large workspaces (few cm3). Finally, our vision for the future trends in the field of Microfactory is briefly introduced.

Toward the personal factory

Production tools undergo a constant process of miniaturization. Technical, economical, as well as environmental reasons motivate this process. The research in the field of the Microfactory and Nanofactory addresses these issues. The question is how far and how fast will this miniaturization go? Does it make sense to have a factory so small that you can put it on your desk, next to you computer, and start to produce whatever you can imagine? Will Personal Factories (PF) ever exist? We first present different scenarios of the Personal Factory. One approach, which is generally favored by physicists, chemists and biologists, consists in the assembly of atoms or molecules, like LEGO-bricks, to build up complex devices (bottom up). We will not follow this approach in this paper. The second approach consists in the 3D microstructuring of the parts and their assembly (top down). We briefly present different structuring technologies that could apply in the PFs. We then briefly present micro-positioning systems developed at EPFL that could be used in assembly in PF.