Christoph Edeler

NanoLab: A nanorobotic system for automated pick-and-place handling and characterization of CNTs

Carbon nanotubes (CNTs) are one of the most promising materials for nanoelectronic applications. Before bringing CNTs into large-scale production, a reliable nanorobotic system for automated handling and characterization as well as prototyping of CNT-based components is essential. This paper presents the NanoLab setup, a nanorobotic system that combines specially developed key components such as electrothermal microgrippers and mobile microrobots inside a scanning electron microscope. The working principle and fabrication of mobile microrobots and electrothermal microgripper as well as their interaction and integration is described. Furthermore, the NanoLab is used to explore novel key strategies such as automated locating of CNTs for pick-and-place handling and methods for electrical characterization of CNTs. The results have been achieved within the framework of a European research project where the scientific knowledge will be transfered into an industrial system that will be commercially available for potential customers.

Open Loop Force Control of Piezo-Actuated Stick-Slip Drives

In this paper a new method to generate forces with stick-slip micro drives is described. The forces are generated if the runner of the stick-slip drive operates against an obstacle. It is shown that the generated force can be varied selectively without additional sensors and that virtually any force between zero and a limiting force given by certain parameters can be generated. For the investigated micro actuator this force is typically in the range up to hundreds of mN. For this reason, the method has the potential to expand the application fields of stick-slip positioners. After the presentation of the testbed containing the measured linear axis, measurements showing the principle and important parameters are discussed. Furthermore, it is shown that the force generation can be qualitatively simulated using state-of-the-art friction models. Finally, the results are discussed and an outlook is given.

Contact mechanics modeling of piezo-actuated stick-slip microdrives

This paper draws a line from early attempts of modeling stick-slip microdrives to open questions from today’s research. As a basis, it contains a collection of substantial investigations on piezo-actuated stick-slip microdrives for nanomanipulation purposes. Friction models showing special characteristics and their mathematical representations are reviewed. It is found that the working properties of stick-slip drives strongly depend on friction characteristics of the contact points between the guiding elements, which is known for years. However, numerous publications in the field of friction and remaining problems — which cannot be explained by known friction models — indicate that there is a demand for even more friction-related research.Former attempts to model stick-slip drives are based on the so-called LuGre friction model, which is shortly presented. An empirical model called CEIM is also analyzed. It is an adaption of the elastoplastic model. The latter can cover not only the phenomenon “0-amplitude’ (described by the authors in recent publications), but also stick-slip based force generation scenarios. Nevertheless, interesting friction characteristics such as the generation of μN forces with stick-slip drives, which are already proven, cannot be covered by known friction models. It is pointed out which characteristics have to be considered.

Modeling of Piezo-Actuated Stick-Slip Micro-Drives: An Overview

This paper gives an overview about problems of modeling of piezo-actuated stick-slip micro-drives. It has been found that existing prototypes of such devices have been investigated empirically. There is only few research dealing with the theory behind this kind of drives. By analyzing the current research activities in this field, it is believed that the model of the drive depends strongly on the friction models, but in most cases neglecting any influences of the guilding system.These analyses are of fundamental importance for an integrated model combining friction model and mechanical model offering promising possibilities for future research.

Simulation and experimental evaluation of laser-structured actuators for a mobile microrobot

This paper describes the simulation, fabrication and evaluation of a mobile platforms actuator, which is the foundation for microrobots. The working principle is based on the mobile platform RollBot. The new feature is the combination of three rolling steel spheres driven by three laser structured piezoactuators, each containing three ruby hemispheres. Because of the piezoactuators special design, the hemispheres stick-slip displacements decrease and enable a more precise control. The platforms properties concerning rigidity, resolution and maximum velocity improve. After an introduction of RollBots and the new actuation principle, a short description of the laser structuring process is given. Several finite-element (FE)-simulations are presented to understand the expected performance of the mobile platform. Finally, measurements of step sizes and maximum velocities are shown. The application of the actuator in a mobile platform proves the derived properties.

Development, Control and Evaluation of a Mobile Platform for Microrobots

Abstract This paper describes the development, control and evaluation of a mobile platform for microrobots. The platform uses laser-structured piezoceramic plates equipped with ruby hemispheres in order to continuously rotate three steel spheres using the stick-slip effect. The spheres roll on the working surface and can thus move the platform in two translational and one rotational degrees of freedom. This indirect stick-slip actuation does not stress the working surface and can even operate on surfaces that are not perfectly flat. The exact geometry of the actuators is analyzed and an open-loop control approach is derived. As there are 27 piezo segments moving nine ruby hemispheres and three steel spheres, both the amplification hardware and the software algorithms need to be carefully designed. A prototype was built and evaluated to prove the concept. Basic data about the platforms properties such as step length, resolution and actuation speed was gathered. The results are very promising as the platform can move with nm-resolution and with velocities of up to 10mm/s.

Simulation and Measurements of Stick-Slip-Microdrives for Nanorobots

This paper presents the results of measurements and simulations of a linear stick-slip axis for a mobile nanorobot for the height adjustment of end-effectors, e.g. microgrippers. The function is dependent on surface condition and friction characteristics. The axis is driven by laserstructured piezoceramics, who generate a dynamic stick-slip motion. It is shown, that the dependency to surface etc. can be partly described by a phenomenon that will be denominated 0(zero)-step amplitude. It is the amplitude, where an actuator displacement is generated, but the final step length remains precisely zero. To investigate several influences on the 0-step amplitude, a test stand was build up. For simulation of friction according to literature dedicated to micro- and nanorobots, friction contacts can be modeled using the LuGre-model of friction. However, the 0-step amplitude is not covered by the model. Furthermore, the dependency to surface condition is not part of actual friction models. Thus, this effect is systematically measured and finally it is discussed how to integrate it into available friction models

Measurements and Potential Applications of Force-Control Method for Stick-Slip-Driven Nanohandling Robots

This paper describes the transition of a recently invented force-generation method to mobile nanohandling robots and outlines future applications. The presented mobile nanohandling robot makes use of miniaturized, piezo-driven Stick-Slip actuators. This allows for very accurate and fast positioning. The drives are fully developed and have proven their performance in fast pickand- place applications. On the other hand, the mentioned force-generation method allows a Stick- Slip axis to exert a dedicated force to any object, which could be useful in many micro- and nanohandling scenarios. However, the method was tested yet only in a testbed similar to the conditions in the robot. Therefore this paper deals with the extrapolation of the results to the real conditions in the robots and discusses benefits and drawbacks. After an introduction of the robot and the force-generation method, measurements are presented and discussed. The paper ends with a sketch of a possible application, which could boost the application potential not only of such mobile robots, but of Stick-Slip-based setups in general.

Laser-Based Structuring of Piezoceramics for Mobile Microrobots

This paper describes the laser-based structuring of piezoceramic actuators used in a mobile microrobot. The actuator has to meet several requirements. Firstly, the achieved positioning accuracy of the mobile platform should be in the single nanometer range. This leads to the use of piezoelectric ceramics, which support this demand. Secondly, as the robot needs to have up to three degrees of freedom (DoF), a complex actuator design is necessary. Thirdly, a small size of the actuator is advantageous in terms of microrobotics. Conventional structuring especially in three dimensions is challenging, due to the refractory properties of piezoceramics and the danger of short circuits or overheating. The presented laser fabrication process uses an Nd-YAG laser and a developed algorithm to structure special actuators. The successful application in a mobile microrobot proves the concept.

Micro-nano-integration based on automated serial assembly

Within this paper an approach for micro-nanointegration of MEMS-based devices or smart miniaturised systems is suggested. In order to overcome the limits of conventional, silicon-based MEMS manufacturing techniques, automated serial nano-assembly processes can be applied. The process chain of such a technique and solutions for key issues with respect to automation are presented. This involves both the key processes and the infrastructure for assembly on the nanoscale. As an application example, results from the automated assembly of carbon nanotube (CNT) based devices in the scanning electron microscope (SEM) are provided.