Arvid Bergander

Touching the microworld with force-feedback optical tweezers

Optical tweezers are a powerful tool for micromanipulation and measurement of picoNewton sized forces. However, conventional interfaces present difficulties as the user cannot feel the forces involved. We present an interface to optical tweezers, based around a low-cost commercial force feedback device. The different dynamics of the micro-world make intuitive force feedback a challenge. We propose a coupling method using an existing optical tweezers system and discuss stability and transparency. Our system allows the user to perceive real Brownian motion and viscosity, as well as forces exerted during manipulation of objects by a trapped bead.

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.

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.

Position feedback for microrobots based on scanning probe microscopy

A cluster of small cooperative robots capable of executing measurement and manipulation tasks is being developed within the scope of a European project. The robots are autonomous and have an overall dimension in the order of 1 cm/sup 3/. In this paper we present the concept of the robots, along with possible locomotion modules based on piezoelectric stick-slip actuators. Tools can be added to the robot for different measurements and manipulations. The integration of an AFM probe on the robot has been realized as a high resolution sensor for localization purposes and for measurements. First experimental results are shown.

Non-contact mesoscale manipulation using laser induced convection flows

Laser induced convection flows is a new and promising method to achieve better manipulation of mesoscale objects (above 1 mum and below 500 mum) in a liquid medium. The temperature gradient created by laser absorption generates natural and thermocapillary (or Marangoni) convection flows. These flows are used to perform the manipulation itself. In this paper, we demonstrate for the first time that large and heavy particles can be dragged using the Marangoni convection flows. Experiments based on these phenomena show that fast and accurate underwater micromanipulation of particles up to 280 mum is possible using only a convergent 1480 nm laser beam.

Flexible micro manipulation platform based on tethered cm/sup 3/-sized mobile micro robots

This paper presents a micro manipulation platform based on several cm3-sized mobile micro robots. The proposed platform consists of a high resolution XY stage with the mobile micro robots on top of it, a camera with a microscopic objective for the local view and a second camera for the overview and tracking of the robots. The concept of such a manipulation platform is discussed and the realized platform is described into detail. Two applications of AFM measurements with an onboard AFM-tool and micro manipulation by adhesion, realized with a similar setup, are discussed

Stick and slip actuators (SSA)

Stick and Skip Actuators (SSA) are particularly well adapted to micro- robotics. A simple design, a very high intrinsic resolution (a few nanometers) and a high rigidity make them especially interesting in high precision micro-manipulations. Moreover, a smart design allows to combine the guiding and actuating function. The mechanical interface between the piezo-elements and the guiding mechanisms in an important point of the stick and slip actuators. The design of this interface and the choice of the material are very important. Both aspects have an impact on the rigidity, which has an influence on the behavior of the actuator. They have also an incidence onf the reliability (lifetime) because the design gives the contact condition and the material the wear resistance. In addition, a loading system allowing to keep the mechanical contact at this interface has a direct effect on the contact pressure. In order to confirm the performance of SSA, prototypes have been developed at the ISR. Their designs have bene made for application in optical microscopy, for manipulators in industrial assembly of micro- engineering products, for micro-factory, chemical and bio-engineering equipment for research or routine tasks, such as testing, screening etc. This paper presents a short description of several SSA made by the IRS and describes the parameters characterizing the stick and slip motion and the mechanical interface.

Haptic feedback of piconewton interactions with optical tweezers

Haptic feedback for micro- and nanomanipulation is a research area of growing importance with many potential applications in micro- and biotechnology. Past research often involves the coupling of atomic force microscopes to haptic devices, but the results are not satisfactory.We propose to adopt a different approach, which consists of contactless manipulation, in particular by using optical tweezers, coupled with a haptic feedback device. In this article, we describe the potential of such a tool and show with some first experiments of stable interactions between micro-particles.

Sensing interactions in the microworld with optical tweezers

Optical Tweezers have become a widespread tool in Cell Biology, microengineering and other fields requiring delicate micromanipulation. But for those sensitive tasks, it remains difficult to handle objects without damaging them. As the precision in position and force measurement increase, the richness of information cannot be fully exploited with simple interfaces such as a mouse or a common joystick. For this reason, we propose a haptic force-feedback optical tweezer command and a force-feedback system controlled by one hand. The system combines accurate force measurement using a fast camera and the coupling of these measured forces with a human operator. The overall transparency allows even the feeling of the Brownian motion.